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August 1, 1952
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CPYRGHT Approved For Release 1999/09/24: CIA-RDP83-00423R002000130013-1 PHILIPS TECHNICAL REVIEW A publication on Lighting, Electronics, X-Ray and other technical subjects PHILIPS PHILIPS RESEARCH LABORATORIES 'Philips Techn. Rev. Vol. 13, No. 1-2, pp. 1-48 ApAMR "Epr Release 1999/09/24: CIA-RDP83-00423R002000130013-1 PHILIPS PUBLICATIONS Philips Technical Review A monthly publication dealing with technical problems relating to the products, processes and investigations of the Philips Industries. It contains articles on Lighting, Electronics, X-Ray and other technical subjects. 32 pages per issue, size 201/2 X 291/2 cm. Published in English, French, German and Dutch. Philips Research Reports A publication containing physical, chemical and technical papers in the English and French languages, relating to the theoretical and experimental research work carried out in the various Philips Laboratories. Philips Research Reports are published in volumes of six issues, each of about 80 pages, size 151/2 X 231/2 cm. Communication News A quarterly publication on transmitters, transmitting valves, line telephony, line telegraphy and automatic telephony. 32 pages per :issue, size 201/2 X 291/2 cm. Published only in the English language. For particulars regarding these publications apply to the publishers mentioned on the back cover of this issue. (Approved For Release 1999/09/24: CIA-RDP83-00423R002000130013-1 Approved For Release 1999/09/24: CIA-RDP83-00423R002000130013-1 VOL. 13 No. 1-2, pp. 1-48 PhIis Technical Review DEALING WITH TECHNICAL PROBLEMS RELATING TO THE PRODUCTS, PROCESSES AND INVESTIGATIONS OF THE PHILIPS INDUSTRIES EDITED BY THE RESEARCH LABORATORY OF N.V. PHILIPS' GLOEILAMPENFABRIEKEN,EINDHOVEN, NETHERLANDS PHILIPS' DIAMOND JUBILEE It was sixty years ago, in the month of May, that the Philips' Lamp Works were established at Eindhoven. The Editors of Philips' Technical Review wish to take part in celebrating this memorable event by issuing this Jubilee Edition. In. the 1941 volume of this Journal one might seek in vain for any mention of the commem- moration of-the 50th year of our Concern's existence. Under the conditions of enemy occupation it had been decided merely to celebrate that event unostentatiously at a meeting of the Management and the executives. Nevertheless that day in May 1941 turned out to be one of boisterous merry-making. Quite unexpectedly the tens of thousands of Philips workers spontaneously downed tools and set out in procession to give vent to their feelings of joy - and to their sense of national pride. Within a few hours almost the entire population of Eindhoven had enthusiastically joined in that demonstration. Although these festivities were abruptly brought to an end by the threat of armed intervention and prohibitions, there are many who regard that May day of 1941 as one of the most memorable days of their lives. Now that, on the occasion of this Diamond Jubilee, liberty and fraternity again reign supreme in our country, there is every inducement for celebration when looking back upon the past, as we shall do in this Jubilee issue. No attempt will be made here to set forth the history of the Philips' concern: as a whole ; this is to be done in some other way. It has been deemed Spontaneous jubilation on the 50th anniversary of the foundation of the Philips' Works. Approved For Release 1999/09/24: CIA-RDP83-00423R002000130013-1. CPYRGHT best Lo confine the scope of this special issue to some aspects of the research work which, from about 1910 on- wards, has been carried out mainly in the Physical Research Laboratory, and to throw light upon the importance of that work for the enterprises of our Concern. Dr. W. de Groot, who has been connected with the laboratory ever since 1923 and thus has been personally as- sociated with the development of this research work for the greater part, having himself furnished valuable contribu- tions towards it, was found pre- pared to write a review on the lines indicated above. It will not lay any claim to being a complete summing up of all research work carried out - such might well prove to be too dry reading - but rather it is to be regarded as an illustrated story about the laboratory, showing in particular the multifarious nature of the problems dealt with and the often unexpected new possibilities emanating therefrom. In conclusion, on behalf of the whole of the editorial staff, we extend our sincere congratulations, on this Diamond Jubilee, to Dr. A. F. Philips, one of the two foun- ders of the Concern, and further Lo the Board of Management and to all who have worked so hard to contribute towards the growth and prosperity of Philips Industries. TIIE EDITORS Approved For Release 1999/09/24: CIA-RDP83-00423R002000130013-1 CPYRGHT Approved For Release 1999/09/24: CIA-RDP83-00423R002000130013-1 SCIENTIFIC RESEARCH OF PHILIPS' INDUSTRIES FROM 1891 TO 1951 With the invention, at the beginning of the wise greatly interested in electric light. Later on nineteenth century, of the voltaic pile and the he conducted negotations for Rathenau in Berlin galvanic battery, providing a source of current between the A.E.G. and the municipality of Amster- with an almost unlimited voltage and a relatively dam about an electric-lighting project, but these small internal resistance, in principle also the negotiations broke down on account of the high price possibility of electric light was created. In 1808 per kWh (fl. 0.60) asked for by the A.E.G. Davy succeeded in passing current through air in 1890, when 6800 are lamps and 118,000 between two carbon rods of a few millimetres incandescent lamps were already burning in Paris, diameter. The tips of the carbons and the gas four electric power stations in Berlin were supplying discharge radiated a bright light. Upon the carbon current to some 3000 are lamps and 70,000 in- tips being spaced a couple of centimetres apart, candescent lamps, and in London a generating owing to convection the discharge assumed the station was being built for feeding 600,000 lamps of shape of an are (an inverted U), which name came 10 candle power, whilst in the U.S.A. 23,500 arc to be used to describe all gas discharges with a lamps and 2,800,000 incandescent lamps had already high current density and with a thermionic cathode. been installed, Ir. Philips conceived the idea of In a certain sense the carbon arc is the precursor starting a new incandescent-lamp factory in the of modern discharge lamps and, in so far as the Netherlands, where others had already been light originates from the glowing carbon tips, also established, among which were the Pope and the of the incandescent lamp. A second forerunner of the De Kothinski works. This plan materialised in the incandescent lamp is the platinum wire brought to month of May 1891 with the opening of the factory at incandescence by an electric current, an experiment Eindhoven. In the course of time G. L. F. P hil i p s which was also carried out by Davy (1802). Carbon- and his younger brother Anton Frederik Philips, are lamps were known about 1850 and, as was sub- who joined the firm in 1895, turned this small sequently disclosed in the famous law-suit between factory, with a starting capital of 75,000 guilders, Edison and Goebel (1893), also electric incandescent into a world-wide concern, the parallel of which lamps had already been made at that time. These is but scarcely found. sources of light were fed from galvanic batteries. It It is not the intention to enter here into the history was not, however, until the invention of the dynamo of this concern, for this will be found in a book (Siemens 1866, Gramme 1869) that electric light which is to be published shortly. Instead of that, came to be introduced on any large scale. In 1879, a review will be given of the development of the on the one hand the differential-arc lamp of Von scientific research, both in the pure and in the Hefner-Alteneck made its appearance and, on the applied sciences, of the Philips Industries and in other hand, Edison's carbon-filament lamp, which particular that which has been carried out in the was demonstrated at the Paris exhibition of 1881, Physical Research Laboratory founded in 1914. together with the machines for generating the current and the means of distributing it. That The first research work connected with the Philips exhibition aroused interest everywhere, and it business was carried out by Gerard Philips was shortly after this that E. Rathenau founded himself. For some time before the factory was started the A.E.G. in Germany. he was studying the preparation of the carbon All this greatly interested the young Dutchman filament and various other processes in a primitive Gerard Leonard Frederik Philips, born 9th workshop at home. In November 1890, when writing October 1858 at Zaltbommel, who was studying to one of the many people with whom he was at the Polytechnical School (now the Technical negotiating for the establishing of the new factory, University) at Delft, where he graduated as an Ir. Philips wrote: "I am able to produce perfectly engineer in 1883. Shortly after that he was given homogeneous cellulose filaments on a business the opportunity to install electric lighting in some scale". Considering, however, what the management ships at Glasgow, and there he made the acquaintance of a rapidly growing young industry involved, and of William Thomson (Lord Kelvin), who was like- bearing in mind that up to 1895 both the commer- Approved For Release 1999/09/24: CIA-RDP83-00423R002000130013-1 CPYRGHT Approved For Release 1999/09/24: CIA-RDP83-00423R002000130013-1 4 PHILIPS TECIINICM, REV'IEW' VOL. 13, No. 1-2 Ir. G. L. F. Philips engaged with his first experiments for the manufacture of carbon flanients from cellulose (1890). cial side of the business and Lite management of the works were in the hands of one man, obviously this research work was at first limited to what was absolutely essential. Technical and scientific help soon became necessary, especially when from 1903 onwards new materials, such as osmium, tantalum and tungsten, the last of which was destined to be the filament material of the future, came to be used in the manufacture of incandescent lamps. About 1907, at the time that incandescent lamps began to be made with squirted tungsten wire, P. N. L. Staa1, A. de Broekert and II. Gooskens*) joined the firm as Gerard Philips's assistants, these being followed, respectively in 1908 and 1909, by the chemical engineers J.C.Lokker and A.dc Graaff, and shortly afterwards by the mechanical engineers IT. de Jong, 11. Ileufel and W. K.oning. In December 1911 the brittle squirted wire was successfully replaced by the more rigid drawn wire. Thus a technical staff of some size was formed, comprising people trained in mechanics and in chemistry, but-it was not long before also the *) lit this review the names of people connected with the Philips Concern are spaced out, while those of others are printed in italics. iteed of physicists began to be felt when, in 1913, a new development was announced in Lite lamp- making world, in the form of the gas-filled lamp. In Lite General Electric Company's laboratory at Schenectady (U.S.A.), where Edisoii's work was carried on and physicists were available, in 1909 Coolidge had found an entirely new method for drawing strong, thin wires of tungsten. There soon followed, in 1913, in the same laboratory, 1. Langinuir's invention whereby a coiled filament Could be brought to incandescence in an inert-gas atmosphere, thereby counteracting vaporization of the tungsten and thus making it possible to heat Lite filament to a higher temperature, so that the luminous output of the lamps could be greatly increased. Within a very short space of time a num- ber of other inventions followed from the same laboratory, such as X-ray tubes with heated cathode and gas-filled rectifying tubes. In November 1913 also Philips brought gas- filled tungsten lamps on the market, under the name of "half-watt lamps". In Lite manufacture of these lamps and also, for instance, in their photometry so many problems arose which lay- more in the domain of physics than in that of chemistry or mechanics that I r. Philips decided to engage a physicist. Thus on 2nd January 1914 G. I b i s t joined the firm in that capacity, and this was the beginning of the Prof. Dr. G. IIolst, after a painting by S. Schroder. Approved For Release 1999/09/24: CIA-RDP83-00423R002000130013-1 CPYRGHT Approved For Release 1999/09/24: CIA-RDP83-00423R002000130013-1 foundation of a physical laboratory. Some months later E. Oosterhuis joined the staff of this laboratory as second physicist. It will be shown how the work of the laboratory established in 1914, starting withthe problems of the manufacture of incandescent lamps, has expanded into such a multifarious programme, from which such a wide variety of other products have been born. In this growth three main periods are to be distinguished: 1) 1914-1923, the period which saw the first world war and during which the laboratory was located in a part of the lamp factory; 2) 1923-1940, beginning with the opening of a new laboratory specially equipped for the purpose (in 1929 it was considerably enlarged) and ending with the occupation of the Nether- lands by enemy forces in the second world war; 3) 1940 up to the present day, covering the years of occupation and the revival of activity after the country's liberation. After studying at the Technical University at Zurich- where he took his doctor's degree in 1914 - Dr. Holst worked for a number of years in the laboratory of If. Kamerlingh Onnes at Leyden, where, inter ilia, he took an active part in the discovery of superconductivity. Thus, in addition to his bent for purely scientific work, Dr. hoist was also technically interested in taking up his new appointment with the Philips' laboratory. Although it was considered as his main task to study the physical questions arising in the manu- facture of' the tungsten lamp, it was felt at the same time that it should not be left at that, but that it was necessary to penetrate to the very roots of the phenomena to be studied. From the tackling of subjects on such a wider basis physical science was primarily benefited, but then this in turn bore fruit for technical science, often in a surprising manner, in the form of improvements of existing products and the opening up of new fields of activity. The study of the tungsten lamp was therefore the starting point: first the behaviour of tungsten wire in the processing, and further its behaviour upon being heated by an electric current to a high temperature in a glass bulb either in vacuo or in the atmosphere of an inert gas; the current had to be passed into the bulb via vacuum- tight and. fused-in wires. Owing to the extensive programme of work the staff soon had to be enlarged. Dr. Hoist received successively the assistance of P. G. Cath, S. Weber, C. Bol, II. C. Burger, C Hertz, Balth. van der Pol, A. Bou.wers, A. E. van Arkel, W. Gciss, J. H. de Boer, P. Clausing, B. Vermeulen, W. de Groot, C. Zwikkcr and others, whilst contributions towards this research were likewise furnished by L. Hamburger, D. J. A. M. van Liemp t, who belonged chemical staff of the works. Lely and to the As regards the physical problems directly related to the incandescent lamp, first of all there was the photometry to be studied, particularly of the gas-filled lamps, since their luminous flux is distributed in space in a less surveyable manner than that of vacuum lamps with a linear filament. In a series of "Communications of the Philips' Laboratory" (1918-1919), which in be regarded as the forerunners of a sense may this journal, Approved For Release 1999/09/24: CIA-RDP83-00423R002000130013-1 CPYRGHT Approved For Release 1999/09/24: CIA-RDP83-00423R002000130013-1 conception- ill Ihl' find of ill it tit illation wira explaitu'd 1(11(1 tu' ba-it'I('ntint- (If utility light fitLing-. projector-- gar lit Ili ll- uill igi(t lautp-. ('te. wee(' d('alt \41111. Of it room hi rid it rnerttal nature 441(- 1114' in4 c - t i- git lioit of rit (liit tittrl. -11 ('11 a- lit, spl-cl rat encrgv di-trihotinn of int?aud('-rant litmlt At that title 11(1nclr".S formula 4t a- -till regardctl with Soule -erptici-4'n and IIll-r(? 44 a- no I houl111( bit451cii Boll r'- tlworv and the lrhenomena of ('lcctrit rnndit ctit it ce iu g1(-e-, fur 4%Itich. in 19?6. tiler 44cr- both awarded 1114' \obt'1 prize. hertz' - ins I'-1 tiun- t4' ill Ito, disci--ed iit ill' next section. 'Ha' nth-t intlturtit rtt re - IIIIuf* the itt4.c-ligation of gas di-charge- ill Ibe period I O 11- I )2.) w1(- till' dlepur insight I11err'bv gained into the plicnonlena of cIteIll 'a! hrait kii iwn. in particular at loot pre-sure. ill Jul r e g 1(- r- between plane, parallel. cold metallic electrode and the deeper kno4tlydge gained of tine Irann-itiun from tit, non- -elf--u-taiue(l to the -elf--u,tained di-charge (Ilol-I. ()u-lirhui-), ()Ic if' the fact.- tlu'reb4- r-tit bli-hell 44it- that, t11e production of electrons in the al0w i- due to tu' action of tlic positive roll- upon Lhe cathode and 110E a' TOIrnsen(1 itnaginetl it to he. a- it result of direct. ionization of till' g1(- 11 111v pusibyl' run-. Tlit fir-t practical ultruute of the in4r-t.igation into gin- di-r11arge- \N ii- the appearance in this period of the Ill lilt glo4% Iantp (IOI") and the tong - lr?n a rc 11(1111) 44iIIt noun - billing ( 1920). 'I'll(- Int l- Ligation of rare -a-c- was facilitated 114 tin' fact that -ince I01(t the Philip-- works load 1wrii ntakilg (under Lhe gltidartee of II. Ii Ii ppo) I lair o5t It 111111 d U).4 gi it and nitrogen. l'roin which the rare g1(-e- could be di-tilled. litr during t(1( 441(4' Ill' importation of' X-ray I-(the- Kit- -lopped medical pract.itioner., ill tit(, Nederland-cot their tube- to the Philip works Fur repair. I'bn- intern-t al-o canto to be taken in the tuhr-. not ullIv ill 4'r-pact to the gas-filled Approved For Release 1999/09/24: CIA-RDP83-00423R002000130013-1 Approved For Release 1999/09/24: CIA-RDP83-00423R002000130013-1 tubes that were then being used but also in the new Coolidge vacuum X-ray tube with a heated tungsten filament as electron source. The study of the manner in which the metal leads could be passed through the glass of the lamp bulb led to the production of ferrochrom- ium alloys which have about the same coeffi- cient of thermal expansion as that of glass and which can be fused onto glass. Prior to this, the leads were of platinum wire, later of iron wire coated with copper; for other glass-metal joints pure copper was used, which differs in expansion from glass but owing to its softness changes shape while cooling. With the new alloys (B o 1, B o u w e r s, B. Jonas) there was no need to make _ allowance for any deformation during cooling, so that the leads and connections could be made much stronger and fusing-in was no longer confined to thin-walled tubes. This led to the construction of metal trans- mitting tubes and metal X-ray tubes. In connection therewith it was of importance that in 1916 Philips had started a glass works of their own (P. J. Schoonenberg). In 1883 Edison had discovered that an electric current flowed through the vacuum between the poles of the filament in his incandescent lamps, a fact which we now know to be caused by electron emission. Following upon Richardson's investigation of electron emission, in 1904 Fleming had invented the diode and in 1907 Lee de Forest had made the first triodes by adding a grid. Simple receiving triodes were produced by Philips in 1917, these being followed by transmitting triodes and diodes for rectifying alternating currents. Soon a systematic study of the phenomena in the radio valve was started. In 1922 Balth. van der Pol (a former pupil of H. A. Lorentz) was charged with radio research*). The new laboratory, situated in a part of Eind- hoven which in 1923 was still on the outskirts of the town, was taken into occupation in November that year by a staff of 15 graduated physicists, chemists and engineers with about 20 assistants, instrument- makers, glass-blowers, etc. By 1939 there were 106 scientists and 360 assistants. The number of publi- cations issued by the laboratory in the period 1914- Since 1949 Prof. Dr. Balth. van der Pol has been Director of the Comite Consultatif International des Radio- communications at Geneva. In connection with the manufacture of radio valves, whereby use was made of the electron- emitting properties of tungsten, further investi- gations were carried out with a view to finding materials which could replace tungsten and give a greater emission for a smaller filament power. In 1921, as a result of new ideas about the theory of atoms, Coster and.Hevesy discovered the element hafnium, related to zirconium. Great expectations were held about the thermionic emission of this ele- ment, and the preparation and study of this new material was energetically taken in hand in the Philips' laboratory. Though this did not culminate in the important results that were expected of it, the chemical and metallurgical experience thereby gained was useful in many respects. The ever-increasing amount of research work to be carried out demanded more space, so that in 1922 it was decided to build a new laboratory, which was completed and taken into use in 1923. Memorial tablet in the hall of the Research Laboratory pre- sented to Jr. G. L. F. Philips on the occasion of his 50th anniversary as Engineer in 1933. On 1st April 1922 Dr. In G. Philips, who during the first world war had had the honorary degree of doctor in the technical sciences conferred upon him at Delft, resigned his co-directorship at the age of 63. He died at The Hague on 26th January 1942. 1923 was about 150 and in the period 1923 - 1940 about 1500. A review of research done in this latter period must therefore be limited to the main lines and some outstanding points. The work begun in the old laboratory was contin- ued in the new under more favourable circumstan- ces. With the larger space available and the increase of staff there was more opportunity for deeper and more far-reaching investigations. It should be mentioned that Dr. H o l s t always left his scientific staff a high degree of freedom. Approved For Release 1999/09/24: CIA-RDP83-00423R002000130013-1 It is impossible, in this short survey, to give a proper account of the various ways in which Dr. IlolsL stimulated his many co-workers. The few places where Ilolst is explicitly named here, certainly give an imperfect impression in this respect. The same applies to I)r. Oosterhuis, who (until 19=16) held the position of Vice-Director and supervised a team of workers engaged in prac- tical radio research. Of course research work was still bound to a cer- tain extent to the factories and their production. The laboratory was expected not only to evolve new Approved For Release 1999/09/24: CIA-RDP83-00423R002000130013-1 ideas leading to new products or to the improve- nicnt of existing ones - ideas which were suitable for patenting - but these ideas had also to be brought to fruition for manufacture. Further, a certain amount of service was called for, such as the calibrating of measuring instruments, examination and testing of materials, etc. Thus, side by side with the purely scientific work, more and more work of it different nature had to be done. This is the reason why the number of publications issued year by year did not grow in proportion to the growth of the staff. For a better comprehension of [lie vastness of the laboratory work this has been divided into five main groups. viz: 1. Light and the production of light, including gas discharges. 11. I lrctroteehnics and radio, including acoustics. Ili. Chemistry, including metallurgy. IV. X-ray investigations. V. 'klatbetnaties and mathematical physics. These amain divisions have to be taken broadly, and furthertrtore there are important connections between them. The X-ray examination of crystals, for instance, forms it link between the groups III and IN', the examination of magnetic materials links up groups II and III, whilst the problems coming under the heading V mostly_ arise from other groups, especially from group II. Approved For Release 1999/09/24: CIA-RDP83-00423R002000130013-1 Approved For Release 1999/09/24: CIA-RDP83-00423R002000130013-1 JULY-AUGUST 1951 1891-1951. I. Light and gas discharges Investigations in connection with incandescent lamps, as far as the new laboratory is concerned, were more or less terminated about 1925 by Zwikker's thesis on the physical properties of tungsten as functions of temperature, which work can be placed side by side with similar work in the U.S.A. In the lamp factory, where a physicochem- ical laboratory continued to be maintained, for many years much important work was done by Van Liempt, Geiss and others in the field of the chemistry of tungsten compounds and the metal- lurgy of tungsten. appeared that an are discharge can take place in a rare gas when there is a potential diflerencc between anode and cathode lower than the lowest excitation potential. Other investigations concerned the n e g a- tive glow discharge, especially the heating of the anode when electrons enter it, and the thermal effects arising at the electrodes of the tungsten are lamp. Important work was by done by F. M. Penning in regard to electrical oscillations in a D.C. discharge in mercury vapour of low pres- sure; in deviation from Langmuir's findings (1925) it was proved that abnormal velocities of electrons in such a discharge are due to the said oscillations. Department for testing materials used in the Philips' Works. The investigation of gas discharges, which had been begun by IIolst, Oostcrhuis and Hertz in the old laboratory, was continued in the new one on a wider scale. Hertz had worked out methods for accurately measuring excitation and ioniza- tion potentials, mainly of rare gases, and estab- lished a relationship between these quantities and the spectrum (term diagram.). The resonance lines of all rare gases were photographed with the vacuum spectograph and their wavelengths accurately determined. Furthermore, following up the investigations of hoist and O o s t e r h u i s, the low-tension are was investigated, when. it For Hertz's experiments an equipotential cath- ode was used which had been coated with barium oxide, obtained by oxidation of barium. applied to the cathode in the form of an azide and then thermally decomposed. The experience gained with these oxide-coated cathodes was of direct use for the manufacture of radio valves. Tungsten as elec- tron-emitting substance was very soon replaced by materials (dull-emitters) which already give ade- quate thermionic emission at a lower temperatue. Oxide-coated cathodes soon came to be used also for rectifying tubes filled with argon and. mercury and for gas-discharge lamps (mercury lamps, neon tubes). Approved For Release 1999/09/24: CIA-RDP83-00423R002000130013-1 Approved For Release 1999/09/24: CIA-RDP83-00423R002000130013-1 to l'tur,iPs rl;cn ulc_~t, It1.~~tt:1K The study of Lite spectra of rare gases had revealed that the atoms of these gases, namely of argon and neon, maN- be in an excited slate Winch cannot he transformed into the ground state by radiation, such a state being called it metastable state. After the departure of hertz in 192.5, 11. B. I)urgelu, who in collaboration with purger and Ornstein had been studying in Utrecht the intensity rules for multildets in spectra, which study was continued in Eindhoven, took up the study of nu?tastable atom,. nun-file tastable state and then to Lite. ground state. It was also found possible by this means to raise the voltage drop of a positive column in a mixture of neon and argon by irradiation with neon light, and even to quench the discharge if the voltage applied is low enough. The effect of Litt, ionization through metastable atoll's is also apparent when investigating the breakdown voltage V between plane parallel plates as a function of the product purl (pu - pressure Tungsten-ribbon lamp.; ucade in the laboratory to serve as light source, for various optical methods of uaeasuring. The second lamp from the left has been ro shaped that, the light reflected by the bulb does not pass through the (plane-parallel ground) windows and thus does not interfere with the measurement. The third hunp from the left has two flat wvindows placed someww=hat obliquely, this being useful for optical pyronietry. These ato.ttu are capable of absorbing and re-emit- ting certain spectral lines which the normal gas allows to pass through unhindered. A ?itlt the aid of this absorption the lifetime of metastable atoms was investigated with respect to the in- fluence of temperature and gas pressure. Owing to their energy of excitation, in it gas l'tix- ture metastable atoms of one atomic kind (say neon) may ionize other atoms (say of argon), such being possible under the condition that the ioni- zation potential of Lite second gas is lower than the potential corresponding to the metastable levels of Lite first gas. In such gas mixtures various factors, such as the breakdown voltage. are greatly in- fluenced bw- small amounts of the readily ionizable ^omponent. This was further investigated by Penning. The fact that- Lite lowering of the 1lreakiioww?n voltage is clue to the action of metastable atoms was proved by denlonstrating that the breakdown voltage of neon, lowered by the addition of argon, rose again when Lite neon was irradiated ww-itlt light which is absorbed by the inrstastahle atones, as a consequence of which these atoms, while emit- Ling resonance radiation, show a transition to a reduced to 0 C. (I - - distance between electrodes), thus determining Lite Paschen curve. Instead of just one ruin 1111111)1 (optimum ratio of ionization and excitation) this curve then shows two minima, owing to an increase of luetastable atoms and thus the formation of "secondary" ions accompanying increased excitation. 'mothe'r anomaly of Lite Paschen curve occurs at values of port - (PotOnain? Normally V increases monotonically with decreasing pool, or, what amounts to the same thing. p,,d decreases monotonically with increasing In the case of hclium it is remarkable that. puff as a function of I; shows a nlnlinlnln and it maximum, so that in a certain range of purl values three critical values of Lite potential are fouled. J't. I., and V, Breakdown only takes place if the applied voltage Va answers to [ i - V n V. or E' --_ V.t. The sank anomaly is found when in the case of stronger currents the voltage is investigated as it function of the current. The study of the relation between the current I and the voltage Vin discharges, as described above, led also to interesting data being collected in regard to Litt- stability of gas discharges, it subject which Approved For Release 1999/09/24: CIA-RDP83-00423R002000130013-1 Approved For Release 1999/09/24: CIA-RDP83-00423R002000130013-1 JULY-AUGUST 1951 1.891-1951 was further investigated later in the Laboratory for Technical Physics at Delft University by Prof. H. B. Dorgelo, Chr. van Geel and. C. Verhagen. Finally there were interesting investigations into the influence of magnetic fields upon discharges. Apart from the fact that the discharge as such forms a "current conductor" which in the magnetic field is subject to a force perpendicular to the current and to the magnetic lines of force, there is the influence of the magnetic field upon the paths of the individual electrons. The latter is particularly manifested at low pressures, where the electrons have a long free path. Following upon Penning's investigations into this field a vacuum meter was constructed in which the current in a gas placed in a magnetic field serves as a measure for the pressure. With this meter direct readings can be taken of pressures be- tween 10-5 and 10-3 mm Hg and, for example, the improvement of the vacuum in pumping installa- tions (such as in the case of the electron micro- scope and the cyclotron) can be followed from one minute to the next. We must now consider the development of gas-discharge lamps. In 1923, following Claude's example (1910), the manufacture of neon tubes for advertising purposes was begun. These tubes had (cold) iron electrodes. Instead of neon, which gives a typical red light, other rare gases, such as helium, were used and also mixtures of a rare gas and mer- cury vapour. The colours could be given more variation by using coloured glass for the tubes. Later on, also fluorescent glass was used and fluorescent powders were applied to the inside of the tubes so as to produce new colour effects. With the intro- duction of the oxide-coated cathode, already ap- plied for rectifying valves, it was possible to make neon tubes for stronger currents and a lower voltage, which came to be used as beacon lights for airfields and as light sources for special purposes (irradiation of plants). Scientific research kept pace with this develop- ment. As is known, in the case of a discharge in an elongated tube Faraday had already distinguished a cathodic part (glow discharge) and an anodic part (positive column), the two being separated by ,,Faraday's dark space". It is the positive column that produces the light in neon tubes, the glow discharge at the cathode being of no importance in this respect. The positive column was thoroughly investigated, theoretically as well as empirically, by M. J. Druyvesteyn, after Schottky had yielded an important contribution to the theory of this discharge. An important concept is that of the electron temperature, which characterizes the velocity distribution of the electrons in the column and can be measured with the well-known probe method of Langmuir. Druyvesteyn was able to deduce that in the absence of cumulative processes the electron temperature is, to a first approximation, proportional to the ionization potential of the gas. Approved For Release 1999/09/24: CIA-RDP83-00423R002000130013-1 Approved For Release 1999/09/24: CIA-RDP83-00423R002000130013-1 ,prong the discharge Iambs with a filling of rare gas and metallic vapour the .odium lamps Occupy it special place. It is well worth -while ondining [lit, developnnent of Lite odium l a tut p in Lite Philips` laboratory. Discharges in sodiunn vapour had already been investigated and used. In 1919, for instance. such it discharge Was described bN R. .I. Strait (l,ord Raylei-gh's son). In 1923 _1. 11. Compton and 1'(ua Voorhis (Westinghouse) investigated a large number of gases and vapours for their ability of producing light and thereby found also the high light-yielding capacity of sodium vapour. They even patented it sperial kind of glass resistant to sodium, but. this did not lead to any useful lamp loving developed. In 1925 C. Hertz dcnuutstrati-d in Lite laboratory it low-tension arc in sodiunn vapour in a bulb o1' about 7 stn diameter. The bulb was fitted with an oxide-coated cathode and an anode. and tails sodium was introduced into the bulb b% electrolysis through the glass wall, with the cathode acting as negative pole and it bath of molten Na\(l.t as positive pole (Warburg's method, 1890). This lamp was placed in it furnace with a temperature of about 250 C in order to maintain it sufficiently high vapour pressure of the sodiutu. Attetttiunt was again drawn to sodium as it source of light when C. Lecher set out Lo improve. in Lite Philips' laboratory. the yield and the colour of the light of neon tubes by introducing a small amount of lithium into the tube. `I'bis was an ob- vious n>_ean-, since front the works of Kirchhoff and Buttsen it had become known that. lithium gives a flame a bright red colour. however, something sluice unexpected happened: the lithium attacked the wall of tine tube and thereby released sodium. so that it sodium lamp was formed unintentionally. This lamp and a number of similar tubes, in which sodium was purposely added to it rare gas. have been used as polariucter lanilts in tin- laboratory for a number of years. Meanwhile investigations conducted by I'irani in the ()srant works had shown that under favourable conditions more than 95?, of the energy absorbed by the column could be converted into sodium. light,, and talus Osrani works also brought it polariuncter lamp on the market. At that time the investigations carried out in. Philips' laboratory had turned in another direction. The use of the mercury lamp as a source of light for medical ray treatment had led to a closer study being made of the connection between vitamin D and rachit is. It appeared that viteunin D could be produced by irradiating ergoster.ine with light of a wavelerngtlt between 2800 and 2900 A, which could he produced by a mercury lamp or a magnesium spark. This cotntplexity of phenomena Was investi- gated by I'.. If. lie(-rink and A. van Wijk. The demand arose for it special source of light for the production of vitamin D and for anti-rachitic ray treatment. Magnesium proved to be the most suitahb' element for this. This led to the construc- tion Of' it low-tension are lamp with a mixture of rare gas and magnesium vapour; the magnesium 1n fit([ sodium latup (for direct current) and a lamp for con- nertion (via a choke) to 220 V' alternating current. each with its varnunt envelope. 'flit- D.C. lamps, in group; of 30 to to ranuerted in series and fed from it rectifier, were used for the first installations for road lighting with sodimn lamps (1932). Approved For Release 1999/09/24: CIA-RDP83-00423R002000130013-1 Approved For Release 1999/09/24: CIA-RDP83-00423R002000130013-1 was contained in the anode and evaporated into the discharge. This opened the way to the construction of other metallic-vapour lamps by the same means. In con- nection therewith, for instance, sodium was investi- gated anew and this led to the production of a low- tension are lamp fed with direct current and filled with a mixture of neon and sodium vapour, which has a favourable luminous efficiency (50-60 lumens per watt) (De Groot and E. G. Dorgelo). In order to give the sodium sufficient vapour pressure the bulb was thermally insulated by placing it inside another, evacuated, bulb. Experimental lighting systems installed in a corridor in the laboratory and later on in one of the roadways on the factory site soon demonstrated the excellent qualities of sodium light for road-lighting purposes. After the construction of the lamp had been improved and it had been given the form of a single bulb contained in a Dewar flask, these experiments were continued on a more extensive scale, inter alia in cooperation with Prof. Dr. H. C. J. H. Gelissen, on stretches of road forming part of the Dutch network of highways (1932). Meanwhile Druyvesteyn and W. Uyter- h o e v e n had been further investigating the posi- tive column in mixtures of sodium and rare gas, whereby it was found that this discharge, in a tube placed in a Dewar flask, is less susceptible to changes in the ambient temperature than the low-tension arc lamp. It is to the merit of Bol, who had also given the low-tension are lamp a shape suitable for manu- facture, that the A.C. column lamp with vacuum envelope was developed into a practical unit which for the greater part can be manufactured mechani- cally, also as far as the glass envelope is concerned. The discharge tube proper has the shape of an elon- gated U. By 1940 more than 100,000 of these lamps had been installed. Abroad too, where similar lamps had likewise been developed, numerous lighting projects were carried out with sodium lamps, some of which by Philips. Lighting with mercury lamps has also to be discussed. Compared with sodium lighting, at first Philips took little interest in mercury lighting. Since the investigations of Kiich and Retschinsky (1907), which resulted in the appearance of the quartz- mercury lamp with mercury-pool electrodes (arti- ficial sun), it had been found that with mercury vapour under high pressure (1-3 atm) a source of light of high efficiency could be obtained. The spec- tral composition of this light shows a striking lack of red and as a consequence colour rendering is inadequate. But with sodium there is still less colour rendering and when this drawback came to be generally accepted for the sake of the other, favour- able, qualities of sodium light (efficiency, visual acuity, contrast) there was every inducement to try out also the mercury lamps. Great Britain set the example by installing experimental lighting with high-pressure mercury lamps, with oxide-coated cathodes, on some highways. Eindhoven, too, very soon started producing these lamps. But meanwhile further developments were taking place. The experimental and theoretical investigations carried out by W. E l c n b a a s very soon made it possible to survey the whole field of mercury dis- charges as functions of the various parameters (dimensions of the tube, mercury pressure, current and voltage). For instance, a principle of similarity could be worked out, whereby the number of essen- tial parameters could be reduced and it could easily be predicted what the behaviour would be of a lamp with certain dimensions and containing a certain amount of mercury. It was again Bo1 who succeeded in drawing prac- tical conclusions from this study and arrived at a very compact construction of mercury lamps, which, however, only became possible after H. J. L e m m e n s had worked out a method of fusing tungsten leads to quartz, using only one intermediate glass. These lamps, only a few centimetres in length and with an internal diameter of 2 mm, were so designed that part of the mercury remained in the liquid state. Owing to the con- siderable heating of the wall of the tube these lamps were cooled with water. The internal pressure amounted to 100 atm and more. These lamps are being used for cinema projectors, in television studios and in searchlights, in general wherever there is no serious objection against the installation of a water-cooling system. Another type, with a determined quantity of mercury which entirely evaporated during the operation of the lamp, had no need of any forced cooling. The equilibrium pressure was 5 to 10 atm. This type of lamp found extensive use for road light- ing. In order to limit the preheating time the lamp proper, which has an internal diameter of 10 mm and a length of 35 mm, was placed in a normal incandescent lamp bulb filled with an inert gas to prevent oxidation of the leads. Notwithstanding the fact that at this high pressure the mercury spectrum shows, in addition to the much widened mercury lines, a continuous background extending into the red, colour rendering is inadequate, just as is the case with the lamp with a pressure of 1 atm. This drawback can be remedied by admixing incandescent light, but then the efficiency of the Approved For Release 1999/09/24: CIA-RDP83-00423R002000130013-1 Approved For Release 1999/09/24: CIA-RDP83-00423R002000130013-1 whole is reduced. Later it was found possible to improve Lite colour rendering by coating the inside of Lite outer bulb with substances which fluoresce under the influence of the ultra-violet rays of the mercury light. Even when corrected with incandescent light or by means of it (red) fluorescing substance, however, for various reasons these lamps are not suitable for indoor lighting. In this direction gas-discharge lamps appeared in a different form. Starting from the low- -pressure mercury discharge, whereby the emission of the visible mercury lines is only small and mainly the ultra-violet resonance lines of 2537 A and 1849 n are produced. these ultra-violet rays were converted into visible light by means of fluorescence. Philips contributed much towards tile. development of these `-TL ' to lies. By coating the inner wall of the discharge tube with it suitable mixture of fluorescent substances (MgWO_t, interest in the more or less forgotten work of A. Korrig (1891) on the subject of seeing at low brightnesses and lie strougly advocated Lite ideas of Schrodinger (1920) in regard to Lite use of the colour spare for colorimetric problems. his division of the visible spectrum into eight sections as a means of judging colour rendering has conic to be of almost universal use, at least in Europe. For the practical application of Lite eight-section analysis a special photometer was constructed by P. W. van Alphcn. II. Elcctrotechnics, radio and acoustics From the manufacture of incandescent lamps a number of important. clectrotecliiiical products have emerged which are related to Lite property of the filament to emit electrons, an effect which, as already remarked, was discovered in principle by Edison and subsequently investigated quanti- (Zii,Mn)ZSiO,i, Cd_B2OS-1In. (Zn,Be,'.47n).oSiO.i. and tatively by Richardson, later also other substances, such as halophosphates) it was possible to produce a white light with it spectral energy distri- bution sufficiently approxi- mating that of daylight or of incandescent light. Such lamps as these. with a gross output of 40 to 50 bu W. are being used more and more for all forms of utility lighting, such as in the home, work- shops, offices, shops. etc.. and for road lighting. J. Voogd and others have been occupying themselves with Lite photomctrv of gas- discharge lamps. The development of gas- discharge lamps with their spectral energy distribution differing so greatly from in- candescent light, their extensive applications for road lighting and the problems of colour rendering all called for a pro- found study of Lite properties of the human eve and Lite faculty of geeing under different levels of brightness. In the Philips' laboratory these prob- lems were energetically tackled by P. J. B o u m a and A. %. KruitIt of. Bounia revived Approved For Release 1999/09/24: CIA-RDP83-00423R002000130013-1 CPYRGHT Approved For Release 1999/09/24: CIA-RDP83-00423R002000130013-1 As a result of this investigation there appeared, as we have seen, first rectifying valves and radio valves with tungsten filament in vacuo, whilst Philips followed the G.E.C. in producing gas-filled rectifying valves with coiled tungsten filament. An important improvement was the replacement of the helicoidal tungsten filament in these valves by an oxide-coated cathode (J. Bruynes). With the introduction of the oxide-coated cathode many more uses were found for rectifying valves, because on the one hand larger emission currents were obtained, thereby extending the field of appli- cation to heavy currents, whilst on the other hand the lifetime of these tubes was so extended as to be dependent only upon the chance of accidental damage (breakage or breakdowns) and not upon exhaustion of the thermionic properties of the filament (J. G. W. Mulder). The field of rectifiers is an interesting example of a case, often seen, where a phenomenon first found as a small effect, so small that its existence might be doubted, ultimately finds application on a scale precluding any doubt as to its reality. The currents studied by Richardson could at first only be measured with a sensitive galvanometer. Now a rectifying valve with an emission current of 100 A is nothing rare. Rectifying valves are now being made for high as well as low voltages. Valves for low voltages (some tens of volts) are used, for instance, for charg- ing batteries and feeding cinema are lamps (D. M. Duinker). In X-ray practice, on the other hand, rectifying valves are employed which can withstand voltages exceeding 100 kV, thanks to their being given a suitable shape. Another important product was the welding rectifier, characterized by a very heavy current (H. A. W. Klinkhamer). Within the scope of rectifier research mention is to be made also of the work done in developing blocking-layer rectifiers, and in connection there- with the investigations with selenium (W. Ch. van Geel, N. W. H. Addink). With the advent of the triode as receiving and transmitting valve round about 1914, radio entered upon a new era, a development to which Philips laboratory contributed in no small degree. It is remarkable how often in the field of radio practice has been far in advance of the theory. The triode proved to answer its purpose well and was already being applied on a large scale ever before the relative problems, such as the calcula- tion of the field between the electrodes and the behaviour of the electrons in that field, had been really mastered; the propagation of the radio waves over long distances had been found practicable long before scientists had got to the bottom of the actual reason for it and before the electromagnetic equations governing the propagation along the earth's surface had been satisfactorily solved. In the long run, however, it is essential to gain the fullest possible insight into the theory of the phenomena, and for that reason Philips have always devoted much attention to their theoretical investigation. Many other problems remained to be A corner of the glass-blowing shop of the Physical Research Laboratory. solved in connection with the practical application of radio valves, and so in the new laboratory radio investigations were divided among a number of groups of research workers. B. van der Pol was charged mainly with the conducting of theoretical radio investigations, whilst the more practical investigations were carried out by E. Oosterhuis, P. R. Dijksterhuis, Y. B. F. J. Groeneveld, H. Rinia, B. D. H. Tellegen and many others. Van der Pot had begun in 1922 with the study of the triode. It had been found that the flow of electrons to the grid and the anode, respectively ig and ia, is a function of the voltages Va and Vg respectively at the anode and at the grid with res- pect to the cathode. A three-dimensional plaster model was constructed with which this relation- ship could be visualized. Then attention was paid to the paths followed by the electrons under the influence of the field and to the secondary emission caused by the electrons impinging on the anode, the effect of which can be demonstrated with the plaster model. Further problems were the distri- bution of the electron stream between grid and anode and the effect that space charge has upon the field; for the study of these problems a found- ation had been laid by the theoretical investigations of Langmuir and Epstein. Approved For Release 1999/09/24: CIA-RDP83-00423R002000130013-1 Approved For Release 1999/09/24: CIA-RDP83-00423R002000130013-1 16 PHILIPS TECTINICAI. REVII:XV The problem of the motion of the electrons, which has always demanded attention in connection with the construction of radio valves, was subsequently investigated by 1'. U. J. A. KIeynen and J. L. 11. .1 011k e r with the aid of it model employing small steel balls made to roll over it sheet of rubber. This device has proved to be of great value in eases where the mathematical approach to the problem is too complex. Another means of circumventing mathematical difficulties was the tneasurintr of fields of complex electrode systems with Lite aid of the electrolytic tank. In connection with the phenomena arising in the radio valve mention is also to be made of the extensive investigation of fluctuation phenu-tt- ena (noise) carried out In- C. J. Bakker and M. Ziegler, which later ou was extended to higher frequencies by It. .1. 0. Strutt, A. van der Ziel and others. Further, there was the investigation made I)- Ii. 13ruining into the secondary electron emission of solids, not only in connection with the occurrence of this emission in ordinary radio valves but also with it view to the construction of special valves iiiwhiclt secondary emission is brought about I-urposely in order to produce special ('fleets. Following upon the study of the radio valve as such, its behaviour was investigated when employed as an amplifier or as are oscillator in it network com- prising capacitances, resistances. self-inductances and mutual inductances. An electric network is it .system which as a rule is governed by it number of liucar differential e(lua- Lions. \TVltll the introduction of radio valves in the network not only are negative resistances intro- duced, which make it possible for oscillations to be generated, but also non-linear terms titer enter into the equations and make the problem more contplica red. Van der Pol succeeded in working out it non- linear diffcrertt.ial equation in a simple form (the an tier Pol equation) which incorporates all essential data involved in the case of oscillations and the liutiting of oscillations in networks. 'l'ltis equation, t?-F(t--t'") F e-.-: 0, contains a- parameter the factor r. which to a considerable degree determines the behaviour of rite solution. It. appeared that within a certain range of values (r 1) the oscillation bears a character differing greatly from the known behaviour. Van der Pol named these relaxation oscillations. As opposed to 'ordinary" oscillations as may occur when the system comprises mainly C's and L's, and which have a sharply defined cycle, while the amplitude depends upon various secondary con- ditions. relaxation oscillations may arise in systems which are governed mainly by C's and R's. In the latter case the amplitude of the oscillations is deter- -uined by the sy,-stent, while their frequency is highly sensitive to external disturbances. Thus a system showing relaxation oscillations, such as it glow lamp shu-rtcd by it capacitor charged by it voltage source via a resistor, can easily be synchronized with a periodical signal, it principle widely used nowadays in television. Small steel balk made to roll over a shcet of rubber give it picture of the paths followed by electrons in, for instance, electronic valves. NX itlt the aid of' relaxation oscillations it is also easy to demultildy frequencies (frequency dividing) and to produce the sub-harmonics, in contrast to the formation of higher harmonics, which can be obtained by connecting non-linear impedances to it normal oscillators- circuit. A, Van der Pol pointed out, the concept of relaxation oscillation is also of biological importance, where the role of' "resistance" is performed by some diffusion phenomenon governing the biological process. Examples are the reaction of plant foliage to the alternation of day and night and the func- tioning of the human heart. Approved For Release 1999/09/24: CIA-RDP83-00423R002000130013-1 Approved For Release 1999/09/24: CIA-RDP83-00423R002000130013-1 JULY-AUGUST 1951 Van der Pol and J. van der Mark succeeded in constructing an electrical model of the heart, built up from a number of glow discharge lamps, capacitors and resistors, with which not only the functioning of the normal heart but also certain pathological aberrations could be imitated. To our minds the medical world was too sceptical about the value of that model at the time. Fortun- ately, however, medical scientists of the present day are showing more and more interest in the results of clectro-physical and elcctrotcchnical work, as for instance in neurophysiology. There are many indications that in the near future closer cooperation between the medical practitioner, the physicist and the electrical engineer, with mutual appreciation for the experiences and views of each, will prove to be of great advantage to all concerned, including the patients. An important part of radio research is that con- cerning the propagation of electric waves and the interaction between these waves and matter. First of all mention is to be made of the investiga- tions relating to skin effect and to the penetra- tion of electromagnetic alternating fields in conduc- tors. The practical side of this subject was made manifest in the manufacture of radio valves, where- by the valve was placed in a high-frequency mag- netic field for degassing various parts mounted in it. It was of importance to be able to predict the degree of heating of the parts (plate, cylinder, grid) as a function of the field strength and of the orienta- tion in the field; this problem was thoroughly in- vestigated in the laboratory by M. J. O. Strutt and others. Of particular interest are the phenomena taking place in bodies of a magnetic material, for there it may happen that above the Curie point (,u ,uo) the product y (,u = ,ue,ur = permeability, 6 = depth of penetration) is small with respect to the dimensions and below the Curie point (,u ' ,uo) large. As demonstrated experimentally by J. L. Snock, this has remarkable consequences when small objects of magnetic material are sub- jected to high-frequency heating. Upon the field strength being reduced the temperature remains high, owing to sufficient power being absorbed even when the field is weak. When, however, the temperature drops below the Curie point the ab- sorption of power rapidly decreases and the field has to be made much stronger to heat the body to a high temperature again. The radiation from aerials was investigated both empirically and theoretically. As far as the experimental work is concerned, extensive measure- ments were taken, fnr inatnnnn, ~F Fh. Feld ctro gthe in areas covered by various broadcasting stations all over the Netherlands (R. Veldhuyzen). Theoretically the problem of wave propagation for a free radiating dipole had already been solved by H. Hertz. When the dipole is placed over an in- finite, perfectly conducting, "flat earth" the field of the dipole and that of its reflected image can simply be added together. Considering, however, that the conductivity of the earth is finite and that it has a finite relative dielectric constant, the problem is much more complicated. For this case Sommerfeld arrived at an exact formula as far back as 1909, but this formula is not suitable for calcula- tions. Therefore at the same time an approximative formula was given for calculating the field strength at the earth's surface. In 1919 the same problem was tackled once more, but in a different way, by Weyl, and in 1926 Sommerfeld showed that Weyl's result agreed with his own. But he then put his approximative formula in a somewhat different form. Much has been written on the question which of the two formulae, that of 1909 or that of 1926, was the "correct" one and what was to be decided by experiment. Important contributions on this subject were given by Van der Pol and his co- worker K. F. N i e s s e n (one of Sommerfeld's pupils), who arrived at a strict solution in a new form, and further by the Americans Norton and Burrows; the exact experimental determinations carried out by the latter proved to be in agreement with the formulae given by Weyl and by Van d e r Pol and Niessen. Another question of practical importance is what part of the energy radiated by a dipole is dissi- pated in the earth, since from that the efficiency of a transmitter can be calculated. This mathematic- ally complicated problem was solved by Niessen (1940) by employing Sommerfeld's exact formula. The problem of the propagation of the waves over a spherical surface has been the subject of an intensive investigation by Van der P o l and II. B r c m m e r following upon Watson's work. Since in the formulae the dimensions of the spherical surface and the wavelength are not bound to certain values, these apply also in other realms of physics, such as for the interaction between light waves and droplets of water (the rainbow). A remarkable theoretical result, for instance, is that the radiation of the rainbow shows polarisation. This can now easily be verified with the aid of "Polaroid" spectacles; it seems that meteorologists had never noticed it. In the investigations referred to, the atmosphere ogeneous medium. Later, Approved For Release 1999/09/24: CIA-RDP83-00423R002000130013-1 CPYRGHT Onnrnvpd For Pplpacp 1999/(19174 ? C:IA P lPR3-M473RM7Ml13M13-1 I'IIILLI's 't'I?:CIINICAL, Itt:Z IEw VOL. 13, No. 1-2 Tire miller contributed important information on propagation in an inhonlogencous atmosphere (tit(- ionosphere, '`ducts"). In Great Britain tit( investigation of the ionosphere had been taken up experimentally oil a wide basis by Appleton, who gave it lecture on this at Eindhoven in 1.930. The root of the problem. for which no solution had then been found, lay in the relation between the virtual height (velocity of light in vacua X half the reflection time) as it function of the frequency and the concentration of free electrons as it function of the height above the earth. From the discussions held at, Eindhoven it appeared that, when ignoring the magnetic field, this relationship is given by an integral equation of Abel, so that. time result. can be written explicitly. At certain frequencies the reflection ti.nte is in- finite. Van der Pot saw in this it connection with the mysterious "delayed ecluts" which at, that time were puzzling man radio amateurs. It is to he noted, however, that Stiirnter had quite it different explanation for this phenomenon and attributed it to charged particles coating front the sun at a great. distance from the earth (10? km and more). A remarkable effect of the ionosphere, discovered at Eindhoven, is the interaction of radio waves of different frequencies. In tile ellipty space, owing to the linearit.v of the 11a-tuell equations, the principle of superposition applies exactly, so that two wave svsLeuls may penetrate each other without airy mutual interference. In the ionosphere, however, the interaction is partly of a non-linear nature, witlc the result that waves propagated through the ionosphere over it powerful transmitter become modulated with the frequencies of that. transmitter. "1'ellegen observed this at Eindhoven in the case of signals from the Bero- Iniinster station, which were subject to interference from the powerful Luxemburg station, the capacitance between the control grid and the anode, which was found desirable on account of the ever higher frequencies at which transmitting station., were w-orking. -With the tetrode thus formed much trouble was experienced from the secondary emission of the anode. Tellegen therefore introduced between screen grid and anode a third grid (suppressor grid) to hold back the secondary electrons. Thus arose the five-electrode valve or pentode, which at first was used as output valve and subsequently came to be applied also in other circuits. On first sight this may not seem to be it very drastic change, but it, has proved to he an exceptionally important improvement, since now, with a very few exceptions, all radio valves are pentodes. Much work has been done in investigating the behaviour of these and other types of valves in various funct.ions, such as for high-frequency and audio-frequency amplification (A. J. Heins van der Ven, J. and others). van Slo.otcn, 11. van Suchteten, Considerable attention has also been paid to the construction of transmitting valves, partly in connection with Lite eniplo}-meat of short waves (1.i-50 nl) for long-distance radiotelephony. An experimental transmitter was built (J. J. N u In a ns), provisionally equipped with a "dummy aerial'', in which the energy normally radiated could be dissipated. A milestone was reached in the history of the laboratory in March 1927, when this transmitter was connected to an aerial and commimicatimn was established with what at that time was the -Netherlands East Indies. This soon gained world fame, especially when, on 1st June 19'2.7, if. M. Queers 11"ilhelntina used the transmitter (station PCJJ) to broadcast an address to the overseas territories. In connection with Lite ever higher frequencies that were being used, there was also the development of the magnetron as transmitting tube. Philips Research Laboratory contributed much towards a proper understanding of Lite working of this tube. The treatises by K. Post ]t a nt u s on the functioning of Lite magnetron with split anode still form the basis for all theoretical expositions in this field. Experiment-, in range finding by means of radio waves of 1 in and smaller generated by a magnetron transmitter were carried out in the laboratory before 1940 ; in the period 1940-'45 this principle was applied on it large scale elsewhere in the form of "radar". The designing and manufacture of radio valves calls for great care and special methods. As higher In addition to this, for the greater part, purely- scientific research it considerable amount of work was directed towards the practical side of radio, in connection with bout radio valves and further radio equipment. Above all, as was only natural, radio valves underwent repeated changes. There was a universal rational dimensioning of the various electrodes. In itlany cases the filament was replaced by an indirectly heated cathode. A second grid was introduced, first as .pace-charge grid and later as screen grid (hull). so as to render the io-19 characteristic less sensitive to anode voltage fluctu- ations and, furthermore, with tike object of reducing Approved For Release 1999/09/24: CIA-RDP83-00423R002000130013-1 Approved For Release 1999/09/24: CIA-RDP83-00423R002000130013-1 II.M. Queen Wilhelmina, accompanied by IT. R. II. Princess Juliana, addressed Her subjects in overseas territories via the Philips' transmitting station PCJJ on 1st June 1927. frequencies came to be used the connections had to be shorter and so different methods had to be found for constructing the electrode lead-ins. The solution was found by applying pressed glass or sintered glass (Lemmens) and special metals for the leads. This development came for a large part from the factory laboratories. At first radio valves and some radio parts, such as high-tension units, audio-frequency transformers and resistance-capacitance couplings, used by amateurs and set makers, were the only radio products manufactured in the works. However, with the increasing popularity of radio broad- casting there was such a big demand for radio receivers that it became worth while to start manu- facturing complete receiving sets. Looking back now, it is hardly imaginable that 25 years ago this was regarded as being something out of the ordi- nary. Almost at once the need was felt for an apparatus that could be worked without batteries by feeding it entirely from the mains. This was made possible by employing the indirectly heated cathode which had meanwhile been developed at Eindhoven. In the construction of radio sets, as already re- marked, a great many problems were involved which had to be solved in the laboratory, in the beginning even in all sorts of constructional details (Bol, C. J. van Loon, J. M. Unk). On the one hand there was a need of certain circuits which had to be as efficient as possible while at the same time being easy to make and to repair, and on the other hand accurate methods of measuring were needed for testing the functioning of experimental circuits. Much attention was devoted to the coils. By making these as loss-free as possible (according to a principle evolved in this laboratory by H. R i n i a) greater selectivity was obtained and a "straight set" could be built with four tuned circuits, which for a long time answered the purpose very well. As the "ether" became more and more crowded with the increasing number of stations working within the allotted frequency bands, so that short waves came to be used for broadcasting, receivers had to be built on the superheterodyne principle. Of great importance was the invention, by Metal leads and supporting rods can be fused into bases of sintered glass in an almost un- limited number and in any order. Approved For Release 1999/09/24: CIA-RDP83-00423R002000130013-1 PIIIL,IPS "I~ 1:CII ~[C.1I, RE II?1~i VOL. 13, 'No. 1-2 Posthumus, of negative feedback, for which patents were obtained already in 1928. This prin- ciple, which reduced distortion due to curvature of Lite valve characteristic,, was very soon intro- duced in Lite Philip, receivers. It proved, however. to have a much wider scope than this, so that at the present day it is being employed in practically all amplifiers and in all kinds of regulating devices, etc. For those cases where it highly constantvoltage (low internal resistance) is required for feeding radio apparatus a self-regulating high-tension supply unit was developed (Ilinia, 11. J. Lin denhovi us). In connection with snkootiling systems for the feeding of radio apparatus retention is to he made of Lite considerable amount of work clone in the field of electrolytic capacitors (Van Cccl, A. Claassen). A difficulty encountered in Lite manufacture of radio sets lay in the lack of uniformity of electric- al networks, especially since there are bout direct and alternating current mains. J. W. Alexander constructed vibrator-converters capable of converting direct voltages of 100 to 200 V into an alternating voltage. Such vibrators are note conn- monly used with car radio sets for converting Lite battery voltage of tt or 12 \ into an alternating voltage of 220 V. Another problem lies in the feeding of receivers in places where no stains are available. In the place of accumulators and dry-cell batteries the tliernio- electric generation of current was thought of, but this is too uneconomical. This suhscqucnth- led to the development of the air engine, which , o rect an y p before long will be able to take Lite place of the means of gramophone records or a Mill t er ape. petrol engine now. used for this purpose. Important. work has also been done in the field of the physiology of hearing. Particular mention In the development of radiotelephony there is is to be made of J. F. Scltouten's investigations also the problem of conversion of the radio signal into the validity of the so-called Ohm's acoustic into audible vibrations of the air, thus into speech law, from which it. appeared that in a mixture of or music. As it consequence acoustics, and especially frequencies which are it multiple of a certain funda- elcctro-acoustics, have become inseparably connec- mental frequency the latter can sometimes be heard Led with radio. In 1925, when under the guidance even if it is not itself present in Lite mixture (the of H. ernneulen Philips started making loud- ..residue" t.heory). speakers, these were built on Litt- electromagnetic Further, L. Blok designed various signal gener- principle, whereby the movement of an armature ators, which have been applied, inter alia, for is transmitted to a diaphragm. Then there appeared audionnetric investigations. the moving-coil loudspeaker, in which the cone- Other developments in the technique of sound shaped diaphragm is connected to it small cylin- reproduction will be dealt wit-11 in the last section drical coil through which the varying signal current. of this review. flows and which is placed in a radial magnetic field. This magnetic field was at first produced by The development of television began already means of a soft-iron circuit excited with direct in the thirties. In its earliest stages a Nipkow current. Philips very soon replaced this circuit disc with =18 lines was used both at the transmitting by it permanent magnet. This development involved intensive research in connection with magnet steel, it subject which will be referred to again elsewhere. The new magnetic materials also made it necessary to give the magnets a different shape, so that attention had to be paid to the de- signing of magnetic circuits (A. Ti!. van Urk). In addition to Lite work involved in the develop- ment of loudspeakers, much work has also been put into the development of power amplifiers, which in turn led to great activity in the field of line telephony (W. Six, If. G. Beljers, J. to Winkel). In connection therewith attention may be drawn to Lit(, various measuring instruments develop- ed in the laboratory, such as a measuring bridge for measuring losses in coils and capacitors, with which phase angles can be measured with an accuracy of 10 `' in it frequency range of 103 - 105 c/s (J. W. K61iler, C. C. Koops). Further research work led to the development of various types of microphones, gramophone pick-ups and gramophone motors, and finally sound reproduc- tion for the sound film and for broadcasting studios. An important part has been played in this by the Philips-~1liller process, whereby it width-nnodu- lated track is cut. in it celluloid tape coated with a lacquer, after which it is scanned by the known optical means. An advantage of this system was that the recording could he played back at once and thus corrected where necessary. In this connection mention is to be made of a system, developed by K. do Boer, for stereo- phonic sound re roduction b th di dl Approved For Release 1999/09/24: CIA-RDP83-00423R002000130013-1 CPYRGHT Approved For Release 1999/09/24: CIA-RDP83-00423R002000130013-1 JULY-AUGUST 1951 1891-1951 and at the receiving end. Subsequently a cathode- ray tube was used in the receiver, whilst the Nipkow disc, still employed for the transmission, was per- fected for televising films (Rinia). Later on the Zworykin iconoscope, meanwhile developed in the U.S.A., came to be used for TV transmission, first for the 180-line system and later for larger numbers of lines (Van der Mark, G. Hepp, A. Venis). Experience was gathered in the construction of amplifiers (J. Haantjes and others) and the build- ing of transmitters (W. Albricht). Experiments In 1937 already a transportable installation for television transmission and reception was completed and taken on tour for demonstrations over a large part of Europe. It could be worked on the system of 405 lines or on that of 567 lines. were also carried out by means of lenses, tube with with projection television employing a cathode-ray screen (M. Wolf). Complete mobile television apparatus in two motor-vans, with was built and installed which demonstrations in Western Europe Copenhagen, Stock- Europe (Budapest, Warsaw). Owing to were given in various places (Utrecht, Brussels, Antwerp, holm) and also in Eastern Bucarest, Zagreb, Belgrade, the outbreak of the war these abrupt end in 1939. to an III. Chemistry It would be saying too much to maintain that all the chemical problems tackled in the Philips labora- tory in the course of time likewise emanated from the incandescent lamp, but for a very large part such is indeed the case, either directly or indirectly. Disregarding the metallurgy of the tungsten and the making of the glass, in the manufacture of the incandescent lamp chemical problems arise from the action of the gases released from the wall of the bulb and the metal leads upon the glowing tungsten filament, whereby traces of water vapour have a particularly disastrous effect. In the dissociation of the water vapour by the filament oxygen is combined with the tungsten and forms a volatile tungsten oxide which is precipitated on the glass wall of the bulb. The remaining hy- drogen in turn reduces this oxide to metallic tungsten. Thus, owing to this "Langmuir's cycle", tungsten is continuously being transported to the wall of the bulb, so that gradually this is blackened. It is therefore essential to remove water vapour and other gases, and this is done by introducing into the bulb a substance, such as phosphorus, which combines with the residual gases into a non-volatile and harmless product. Such a sub- stance is called a "getter". In radio valves, where phosphorus cannot be used on account of its high vapour pressure and residual gases are moreover obnoxious because in the ionized state they affect the oxide-coated cathode and give rise to grid currents, and in X-ray tubes, where residual gases increase the risk of breakdown, metals like barium and zirconium are used as getters. Even though the bulb of an incandescent lamp may not contain any gases attacking the filament, still evaporation of the tungsten takes place. In course of time this evaporation likewise turns the bulb black and thus the yield of light is reduced. Furthermore, the filament itself is reduced in thick- ness and as a result eventually collapses. The same applies in the case of the gas-filled lamp. The pre- vention of the evaporation by the gas-filling as such is offset by the filament being heated to a temperature so much higher that the lamp has about the same lifetime, so that the only advantage gained is the higher efficiency. The manner in which this evaporation of the tungsten takes place differs according to whether the lamp is filled with gas or evacuated. In a gas-filled lamp the tungsten atoms come into collision with the gas molecules time after time, so that they have an opportunity to combine into aggregates which move about in the gas in the form of sub- Approved For Dnln~cn 1999/09/7A CIA_RDP83_00123 002000130013_1 CPYRGHT microscopical flocculations and eventually settle upon the wall of the bulb. Owing to convection this shows a preference for that part of the latup which in the burning position is uppermost. thus not Lite part through wlticlt most of Lite light passes. With the vacuum lamp the situation is different: the tungsten atoms travel in a straight line from the filament to the inner wall of Lite bulb. It can be imagined that upon striking tile glass wt all Lite tungsten atorn is repelled like it minute metal ball. but we know that ultintatef.v it adheres to Lite glass, so every time Lite atom strikes against [lit- wall it must lose some of its kinetic energy.Lartgnucir's conception was that upon collision with Like wall Lite atom tetuporarily adheres to it and is then. as it were, again evaporated, thus implying a certain "adhesion time". By accurate experimentation this has been confirmed by f:lausirtg. It is true that in the case of cadmium atoms oniv an upper limit (10 " see) could be found for this adhesion time, but in the case of argon atotus on glass at temperatures of 80 to 90 K adhesion times of 10 to 10 sec were found. This matter of the evaporation of tungsten has been dealt with at. sotne'lengt.h because Lite investi- gations carried out in connection therewith formed an introduction to further investigations into the adsorption of tungsten atoms and tile resultant absorption of light. So long as the tungsten atoms remain isolated on the wall of Lhe bulb there is no appreciable absorption of light. but the position is different when they form a continuous laver of metal. In order to minimize Lite absorption of light, therefore, before the mount is fused into Like bulb the filament is sprayed not only with the getter but also with a little salt, say CaF.0. As soon as the filament is heated to a high tempera- ture this salt evaporates and is precipitated on Lite wall of the bulb as an invisible thin layer. The tungsten atoms conking from the filament shoot into this laver of' salt, Like particles of which keep the atoms separated. so that very much less light is absorbed. About 1920 little was known with certainty- about the effect of such layers of salt. Investigations into their action carried out in Philips laboratory. mainly by J. 11. de Bocr. extended over a period of more than 15 vears. It. has thereby been found that the laver of salt is not to be regarded as a homogeneous mass but as an agglotuerat:ion of minute crystal lamellae about 10 " cut thick lying criss-cross one on top of the other and thus forming a very large active surface, tens of times greater than the surface of Lite glass covered by them. The tungsten atoms are adsorbed on the surface of Lite crystals. 'I'll(- intensive study of Lite adsorp- tion of atoms and molecules (e.g. caesium and iodine) in such layers of salt (Dc Boer, C. J. Dippel, C. F. V'c e n e ni a n s) has yielded very important results. Metals like caesium may be adsorbed also on tit(- surfaces of metals. in which case they have the property of reducing the work function of the metal and thus increasing the electron emission, bout the thermionic cnntission and that brought about by irradiation with light - photo-electric effect. By oxidizing the adsorbed laver and again precipitating caesium onto Lire laver of oxide it is possible to produce complex layers with an exceptionally strong photo-electric effect (M. C. Tc v e s). The study of this emission was of import- ance for the construction of photocells, for which there was a need in connection with the sound film. '1'lo' deeper insight gained into the nature of these lavers opened up new possibilities, such as the entplovinent of the *'light transformer" for converting infra-red rays into visible light (Hoist, De Hoer. Tcyes), Lite construction of tike electron- multiplying valve and, later. the television pick-up tubes. 't'ile investigations into Lite vaporization of CaF2 also led to other compounds, such as ILiB03, K..B1' , being tried out for tile. same purpose, as a result of wlueh the volatility of various compounds was studied.. Wlkv, it may be asked, is NaCl for instance a substance having a high melting point and it negligible vapour pressure at room tempera- ture. whereas WC1G is a substance that readily melts and is easily evaporated? From the point of view of the theory of heteropular chemical com- pounds Like answer is simple. The molecule of NaCl is built up from it positive sodium ion and a negative chlorine ion, which together form an ch?ctric dipole, so that: two i aCl molecules exercise a very strong attractive force upon each other. In the case of \VCls. on Lite other hand, the central metallic ion is surrounded by six chlorine ions screening off' Lite charge of the central ion, so that there is no great attraction between neighbouring molecules. The theory of the lie terop o far chemic- al b u nd was formulated by Kossel in 1920,following upon Bohr's work. It is mainly due to the work of \'an Arkel in this direction that a more or less coherent explanaLion was established for the most important facts in anorganic chemistry, an explana- tion that, is of great value as a basis for chemical thought and for education in chemistry-. It is fortu- nate that this was more or less completed before Approved For Release 1999/09/24: CIA-RDP83-00423R002000130013-1 CPYRGHT *ppiaved Fa. Release i999te9t24. el*-Rl3P89-ee429Ree2E1ee1 See! 9-1. JULY-AUGUST 1951 1891-1951 the conception of the homeopolar bond came into more prominence as a result of the development of quantum mechanics. Thus the one-sided-hetero- polar aspect could gradually be introduced into the new system without losing its value. In connection with these investigations the energy of formation of a number of molecules and crystal lattices was calculated and the relative stability of various molecule models investigated. known that WC16 and hydrogen on the surface of a heated tungsten filament may react one upon the other and form tungsten, which is deposited on the wire. When a mono-crystalline wire is taken (Pintsch wire) also the growing metal becomes a mono-crystal. In the Philips laboratory it was found that dissociation of WC16 at elevated tempera- ture takes place also without hydrogen; attempts were made to produce other metals in the pure Measuring the spectral transmission of various materials in the ultra-violet range. On the right the source of ultra-violet radiation and the m.onochromator. In the centre, in a screening cage, the measuring apparatus with photoelectric cell. The above conceptions were also applied to the relation between physical properties of homo- logous organic compounds, as for instance the relation between the boiling points of CH4 and of the compounds obtained when replacing in CH. one or more hydrogen atoms by atoms of F, Cl, Br or I. Subsequently, after Van Arkel's appointment as professor at Leyden, this investi- gation was extended by him and his students to a large number of other compounds. Also worthy of mention is the study of the dielectric behaviour of organic dipole molecules in solution, which led, inter alia, to the "Van Arkcl and Snook formula", which was later investigated theoretically by Onsager and by Bdttcher. The study of the volatility of metal compounds had also important technical consequences. It was state in this way. Perhaps the most striking result was the preparation of titanium, zirconium, hafnium and thorium from their iodides by precipitating the latter on a thin tungsten wire as core (De Boer and J. D. Fast). In this way titanium and zirconium, known as being greyish brittle substances of a doubtful metallic character, were obtained in the form of fine lustrous metallic products. The rods, consisting of a few large crystals, proved to be highly ductile, so that they could be drawn into wire and rolled into foil. This is particu- larly of importance in the case of titanium, consider- ing the interest taken in this metal in recent years. Ductile zirconium has found important applications in vacuum technics. Applied to the anode of a transmitting valve it proves to be an excellent getter, on account of the almost unlimited capacity Approved For Release 1999/09/24: CIA-RDP83-00423R002000130013-1 t^.PYRC;HT 21 PHILIPS TECHNICAL REVIEW,' of this metal to adsorb oxygen and oilier gases. The oxygen taken up in the metal has a negative charge, as appears from the fact that. in an oxygen- further investigated by Van !lrkel, Snock and charged rod of zirconium through which a direct current is ]sassed the oxygen migrates towards Lite positive pole. The knowledge of metals and their interaction with gases proved to be of great value to the labora- tory staff when it was decided to nta nufacture welding rods (J. Sack, P. C. van der V illigen), in addition to the welding rectifiers and rectifying valves already being produced. The study of tungsten wire and the behaviour of tungsten in processing led to extensive research in Lite domain of reervsLallizat.ion. A substance particularly suitable for this is aluminium, which is easily deformed and recrystallized at. co-nparaLive- Iv low temperatures ( 600 C), while the process of this recrvstallization can be followed by etching in aqua regia after removal of the superficial oxide with caustic soda or hydroll uoric acid. This simple technique. supplemented by crystallographic study (W. G. Burgers, J. F. It. Custers). led to a deeper insight into the essence of the formation of crystal nuclei. This study is still being continued at the present. day by Prof. If'. G..Burgers in the inorganic- chemical laboratory of Lit(, Technical University at Delft. Finally, in connection with applications in Lite field of clectroteclutics and acoustics (transformers, loudspeakers), extensive research has been carried out in regard to Lit(- magnetic properties of metals, particularly of iron and iron alloys (G. J. Sizoo, W. F. Bra-tdsina, Elc-abaas, .Jonas, Snock, Six, G. W. llathenau. J. J. Went, 11. J. Meerkamp van Hoiden). Special products, Lite fruit of years of'study in Lhis domain, were the rolled nickel-iron ("Fernicube") with strong anisotropic properties, for loading coils, and magnet steels with exceptionally high coercivity and high value of the (111311;, product, which are widely used not only in loud- speaker magnets but also in pocket and bicycle dynamos. Of importance for the investigations both of magnetic and non-magnetic metals was the work done by Snock in studying Lite magnetic after- effects of iron, whereby it. was found that these effects are related to the presence of traces of carbon and nitrogen, which influence not only the magnetic but also Lite elastic after-effects. Both these are governed by a sort of diffusion of C and _N atoms present in interstitial places to neighbouring interstitial places. Other materials studied at Lite time in the labora- tory are Lite ferrites, which since 1934 have been 1:..1. W. Verwev. Preparation of magnet I eel. IE;mpLy?ing the furnace in which the alloy Inn. been melted by induced high-frcquenev currents. This led, inter alia, to the view (De Boer and Verwey) that it substance like Fe3O4 derives its conductivity from Lite fact that. ions of one and the same element but of different valency are present in crv stallographically identical places and thus make it possible for an electron to pass over from one ion to another. In tine course of the resultant investigations our research workers became familiar with various problems of the solid substance, in particular with oxidic systems, of which the spinets form an inter- esting sub-group. `1'111' latter were further studied both in respect to their electrical properties (Ver- wev and others) and with regard to their magnetic properties (Snock). The study of the electrical properties led to the development of semi-conducting materials. while that of the magnetic properties yielded the important magnetic material "Ferrox- cube", which will be dealt with later. Approved For Release 1999/09/24: CIA-RDP83-00423R002000130013-1 C:PYRGHT-- - - - - Release i999i09/24. el*-RDPO3-004238002000130013-1 The previously mentioned work by De Boer and others on the adsorption of atoms on crystals was extended to cases where atoms are built into a crystal lattice, a subject to which much attention was devoted in Germany by Pohl and his pupils. What is particularly due to De Boer is the disclo- sure of the fact that the place of a lacking negative ion in an ion lattice may be occupied by an elec- tron and that, at the cost of only a little energy, this electron may be brought into a state in which it acts as a conduction electron. It was at that time that the programme of work on solids was given shape, which later on was to occupy the minds of such a large part of the scientific staff of the laboratory and comprised, among others, the investigation of luminescent substances. The luminescent substances (lumin.ophores or phosphors) used for converting the ultra-violet light of gas-discharge lamps into visible light are prepared according to methods evolved by Lenard round about 1890. These investigations in the field of luminescence are to be regarded as classical and have not yet lost any of their value. They revealed in particular the fact that the luminescence of sub- stances like zinc sulphide is due to the presence of extremely small admixtures of certain metals, such as copper and silver (activators). When it became evident that large quantities of luminescent materials would be needed for light- Phosphors are exposed to an electron beam in a vacuum tube and tested for their fluorescing properties. ing purposes Philips began to take up the manufacture of these substances and, at the same time, the study of the phenomena of luminescence. This study covered both the physical aspects - such as the spectral composition and the intensity of the luminescent light as a function of that of the incident rays, the decay of luminescence as a function of time in the case of discontinuous irradiation, the relation between luminescence and temperature, luminescence under the influence of cathode rays and X-rays - as well as the chemical aspects, such as the influence of the composition and of the conditions during preparation upon the lumines- cence, and the influence of admixtures (quenchers, sensitizers) upon the inten- sity of fluorescence. Often the chemical and the physical problems are so closely interwoven as to be inseparable, so that close cooperation between physicists and chemists or the combination of physicist and chemist in one person is essential for these investigations. Important physical results lay in the deeper insight thereby obtained into the mechanism of fluorescence and phos- phorescence, the transfer of excitation energy in phosphors and the relationship between persistence and quenching as a function of temperature (F. A. Kroger, H. A. Klasens). Chemical results lay in the deeper in- sight gained into the properties of zinc sulphide and related compounds and of substances such as Zn2SiO4-Mn2SiO4 and other manganese phosphors (Kroger). Approved For Release 1999/09/24: CIA-RDP83-00423R002000130013-1 CPYRGHT In Lite foregoing some cases have already been mentioned where organic compounds were studied. Mostly these concerned simple organic molecules which are very closely allied to the inorganic compounds. But work has also been done in the field of or- ganic chemistry proper, na-nely in that of compounds with large molecules. such as gelatin. cellulose, proteins and synthetic resins. Gelatin was thor- oughly studied because this substance serves as base for Lite Philips-Miller tape (Diit pc1, A'erin eu- len) used for sound reproduction; this tape con- sists of a celluloid carrier with it transparent coating of modified gelatin. covered by it non-transparent layer of IIgS-sol in which the cutter of Lite recording apparatus traces a "sound track". Artificial resins were originally studied with a view to Lite possibility of using these materials for making Lite bases of radio valves and loudspeaker baffles, and later for snaking various parts and the cabinets of radio sets from these materials. The. phenols hardened with formaldehyde, which had been named bakelite after Lite Belgian chemist Baekeland, were. placed on [lie market by Philips in a large number of varieties under the trade name "Philite". A third group of organic compounds, the diazn compounds, was intcosively investigated ill the Philips laboratory when it was contemplated to produce dye-line paper, in addition to the mercury lamps destined for the dye-line process. With the aid of these compound, in various carriers, such as cellophane, paper. cellulose esters, etc., materials for photographic reproduction were pro- duced which, via conversion of the products of dissociation through light into a developable latent. metallic image, ultimately vield silver images with a resolving power of 1200 lines per min. which appear to present interesting possibilities of appli- cation (Dippel, R. J. II. Alink, K. J. Keuning). Attention was also given to tile study of colloid- chemical problems. One result of these invcatiga- tions, which was of importance for the manufacture of radio valves, was a new method of coating cathodes with a layer of oxide, covering then by means of electrophoresis with finely distributed carbonates of barium and strontium, which are afterwards turned into oxides. Also the insulating layer around the filament of utdirectly-heated cathodes is applied in this way (De Boer, L erwev, II. C. IIautaker). This concludes Lite review of chemical research in Lite Philips laboratory prior to 19.10. A number of investigations carried out with metals and with non-magnetic and magnetic ceramic materials, glass and semi-conductors will be dealt with in Lite last section. IV. X-rays From the radio valve it is but one step to Lite X-ray tube. Any diode is in principle a source of X-rays, and it does in fact become so when Lite electrons strike Lite anode with sufficient energy. With Lite X-ray tube problems arise which are simi- lar to those encountered with the radio valve, such as Lite shaping of Lite electrodes with respect to the nature of Lite electric field, Lite paths followed by primary and secondary electrons, and Lite focus- ing. To these are added the typical problems connec- ted with high tensions, as for instance Lite efficient distribution of potential differences. Since only a small fraction of the electron energy is converted into X-rays and the rest is absorbed in the anti- cathode in the form of heat, it is a great problem how to carry off that heat: by providing for suffi- cient dissipation of this heat and giving Lite anti- cathode it suitable construction it has to be ensured that in the focus Lite material struck by Lite clec- tro-ts does not melt. Of physical importance is the measuring of Lite intensity of the X-ravs and Lite strength of the dose. Much attention has therefore been devoted to this problem by A. B o u iv e r s, who took up X-ray research in the Philips laboratory in 1920. I,t the construction of X-ray tubes one is. con- fronted with such problems as Lite safeguarding of the users of X-ray apparatus against scattered ravs and high tension, the raising of the specific load. the requirement of easy handling, and Lite applications in connection with a proper formula- tion of the optical requirements which Lite apparatus has to answer; these applications may be of a medical (diagnostics and therapy), a physical (examination of crystals with X-rays) or a tech- nical nature (examination of materials). An important, discovery was Lite possibility of fusing glass to metal, for which the chrome-iron already -nentioned was used. This made it possible for U0uwers to build rugged X-ray tubes, which, since the part where the rays are generated is en- tirely enveloped in metal, afforded the maximum of safety against undesired radiation and, moreover, allowed of it simple safeguarding of the user against high tension by earthing the metal shield. Tubes came to be developed for still higher voltages and for larger powers, both for diagnostic purposes and particularly for therapy. A special form of X-ray tubes which should be Approved For Release 1999/09/24: CIA-RDP83-00423R002000130013-1 CRXRr_WT Approved For Release 1999/09/24: CIA-RDP83-00423R002000130013-1 mentioned is the rotating anode tube, which was first developed by Bouwers in cooperation with J. H. van der Tuuk. The problem of the dissipation of heat in these and other anodes was thoroughly investigated by W. J. Oosterkamp. Further, special tubes were designed for crystallographic re,arch with the aid of X-rays,ip.-;;`nich the anticathode was mark= of special materials, such as molybdenum, copper, iron, etc., because these are required to yield approxi- mately monochromatic rays of a known wavelength. In the beginning all X-ray tubes were made in the laboratory, but later a separate factory was opened. The main features in the manufacture of X-ray tubes are well studied and well applied technology (getters!) and the exercising of extreme cleanliness in handling the materials. Apart from the development of the X-ray tubes themselves, that of the apparatus for supplying the high tensions required for the working of the tubes, as also that of the control desks, forms a considerable part of Philips' activity in the field of X-rays. Often alternating voltage has to be trans- formed into direct voltage, for which special rectifying valves are needed, One of the first practical executions (1937) of a cascade generator, for 1.7 MV direct voltage. which formerly had a tungsten cathode but now have either an oxide-coated cathode or one of thoriated tungsten. Side by side with the aim towards higher tensions and greater powers, provision was also made for cases where a relatively low voltage and a small 67064 One of the first experimental X-ray units of very small dimen- sions (1933), a forerunner of the "Centralix" and "Oralix" apparatus. power suffice. Small X-ray apparatus was therefore developed in which the tube and the transformer are incorporated in one single unit. Such units serve as portable apparatus for diagnostic work and, for example, as X-ray apparatus in dentistry. It has even been possible to produce a complete X-ray apparatus so small that it can be carried in the pocket, and yet it yields a satisfactory beam of X-rays. From investigating current sources for high vol- tages B o u w e r s arrived at the principle of voltage multiplying by means of a cascade circuit. Subsequently it appeared that this principle had already been recorded by Greinacher and that it had also been applied by Cockcroft and Walton for nuclear-physical research in the Cavendish laboratory. As a special feature of Philips' develop- ment in this field is to be mentioned the elegant solution of the heating of the filaments in the valves by high-frequency current (A. Kuntke). A number of high tension generators of this type, for tensions Approved For Release 1999/09/24: CIA-RDP83-00423R002000130013-1 r pyRnuT Small rectifier in cascade ronncction. ronsi.ting of selenium valves and capacitors. Connected to 2211 r altcruaItug voltage it yields 12011 V direct \nlIagr, with which, for itt taurr, a radiation counter tube ran be fed. up to 2 MV, have becu Intilt at Eindhoven for insti- tutions in several countries. Once it became. possible to generate high tensions it was only a logical setlueuce to take up also re- search in nuclear physics. Il o u we rs and F. A. 11 e y ii designed an ion-accelerating tube with which the constructed by Penning, whereby deuterium ions the working of this apparatus, scientific nuclear research work was carried out with it. In the course of that work lie vu discovered the. (it, 21t) reaction with Lite elements Cu and `Ln, by which reaction the nucleus is struck by one neutron and yields two neutrons, this being accompanied by the for- ination of it radioactive isotope of the same atomic number but lighter than the basic isotope. In 1939 A. IL W. Aten, Bakker- nd IIevn studied the transmutation of uranium and [li ium by neutrons. In this connection mention is also to`i;cMade of a neutron tube without a separate ion source are accelerated in a gas discharge and Lite target is placed in the discharge tube itself. In order that sufficiently high voltages can be applied and the free path of the ions made large enough, the tube is filled with deuterium under it very low pressure and the discharge space is placed in a magnetic field so as to constrain the electrons to follow long paths. just as in till' case of the manometer described earlier. thus making it. possible for the discharge to he maintained under the low pressure. Installation for X-ray therapy, working iaitli it voltage of l-00 kV, supplied in 1911 to the Academic [lospital at Groningen. ions of' deuLeritim, formed in a separate ion source. could be accelerated to an cttergl of 1.2 11e\ and focused upon a target of bervlliuni or lithium. Thus a powerful neutron source is formed by means of which materials placed in its vicinity can be made radioactive. In order to gain experience in Approved For Release 1999/09/24: CIA-RDP83-00423R002000130013-1 PHILIPS TF.CII.,\fcm. REVIEW VOL. 13. No. 1-2 V. Mathematics and theoretical physics With the growth of the laboratory more and inure interest was taken in theoretical-physical and mathematical research. whereas on the one hand. besides development work for practical applications, experimental physical research is Approved For Release 1999/09/24: CIA-RDP83-00423R002000130013-1 CPYRGHT Approved or Release 1999/0 - - - necessary to obtain a deeper insight into the prob- lems, so on the other hand fruitful experimentation is only possible when at the same time the necessary attention is devoted to theoretical physics. This implies that the necessary mathematical apparatus has to be mastered and where possible further developed. This applies more or less to each of the groups already dealt with. Both the study of gas discharges and radio research, as well as the physico-chemical studies and the work on X-rays, had each in turn their own mathematical problems. In regard to gas discharges there was the mathe- matical treatment by G. Hertz of the diffusion of electrons in an electric field. The method followed by Hertz has served as an example for many theo- retical calculations in this field (D r u y v e s t e y n, Penning, De Groot). This brought us a step nearer to the ideal: to explain the various forms of dischar- ges with the aid of a small number of data concern- ing elementary processes (the probability of exci- tation and ionization in the case of collision of electrons and atoms, etc.), in much the same way as the kinetic gas theory relates the measurable quantities, such as pressure and temperature, to the elastic collisions between gas molecules. Further it has already been seen, for instance, that with the aid of considerations of similarity the phenomena in discharges in mercury vapour of high pressure can be reduced to one single aspect. Once he had become familiar with this method of calculation, and following upon a publication by Nusselt (1916), Elenbaas was able to apply similar considerations to the phenomenon of thermal emissivity through natural convection. The need for this arose from the manufacture of blocking- layer rectifiers in connection with the dimensioning of cooling fins, but also other problems of convec- tion can be considered in this light, such as the heat dissipation of horizontal cylinders, which brings us back to the gas-filled incandescent lamp designed by Langmuir. The part of the work programme that lent most stimulation to the practising of mathematics was radio. Mention has already been made of important mathematical problems which arose in connection with the propagation of waves. Van der Pol took up the study of the wave equation and the potential equation, not only in three dimensions but also in the cases of fewer or more than three dimensions. As is known, the propagation of waves can be treated in two ways, either as a whole, by the solu- tion of a "wave equation", or by an approximativc solution of the behaviour of a narrow beam or "ray". The latter method is well known from the theory of light; the image produced by a lens is not usually studied by starting from the representation of a wave but by investigating how the rays of light are refracted by the lens. In the case of radio waves Bremmer has investigated in how far results can be reached with this geometrical-optical approximation. In addition to radio, particularly the theory of atoms has formed grounds for excursions into the field of mathematics. It is remarkable how closely the mathematics of these problems are associated with the mathematics encountered in the field of radio and acoustics. In 1925 Schrodinger showed, for instance, that the motion of an electron under the influence of an electromagnetic field has to be described by a wave equation which shows a certain resemblance to the equation representing the propagation of light or sound in an inhomoge- neous medium, and that the classical consideration of an electron as a "particle" describing a "path" is to be compared to that conception as geometrical optics compare to wave optics. The quantity used by Schrodinger to play the part of "field strength" or "deformation" of the medium, and which he denotes by 11, has the property that 1I 21 is a measure for the probability of finding a particle at a certain place. Owing to the similarity between these problems and those of the propagation of waves encountered in radio and acoustics, theorists in the respective fields soon understand each other and find interest in the results of each other's work. In dealing with the problems connected with oscillations in networks or the propagation of radio waves one mostly has to do with more or less com- plicated differential equations. Heaviside showed that in many cases the differential symbol, d/dt, can be regarded as an algebraical quantity (usually represented by D), with which ordinary arith- metical operations can be carried out. In this way he was able to derive deep-lying results by simple means. This operational or symbolic calculus was at first received with much scepticism, but later Carson (1926), for instance, found it to be justified. What Carson's formula amounts to is the furnishing of a function f(p) corresponding to a function h(x) by the Laplaec transformation: 00 f(p) = p f cPx h(x)dx. 0 The shape of f(p) depends, of course, upon h(x). This function f(p) is said to the be "image" or the Approved For Release 1999/09/24: CIA-RDP83-00423R002000130013-1 "translation" of the function la(x) and it is denoted by the symbol: f (p) . It (x). The functions x", C', sin x and cos x, for instance, have as their images is I P P P` and P P 1' j,_ 1 p-'; l from which it is to be noted that often the image is a simpler function than the original. 'T'hus relations between different originals can be deduced via simpler relations between their respective images. an der Po1 and Niessen have worked out it great many images and front them derived new relationships hetweenfunctions. 1lention Itas alreadti In the course of development (if carrier telephony it was necessary to investigate how the bcluniour of electric filters is affected by losses. This behaviour is governed by the Laplace differential equation. -l graphical solution of this equa- tion, with given boundary conditions. is obtained by stretch- ing a film of soap between three-dinn?n.ional curve, corres- ponding to tlue boundary conditions. The case illustrated here relates to a bandpass filter (frequency limits cut and 0)_); k is a measure for the losses, a a measure for the damping. been made of the problem of the aerial over the flat earth, and for that, Lou, the symbolic calculus was employed, with the further help of the methods followed in the theory of the functions of a complex variable. These results were obtained with the aid of the one - s i d e d Laplace integral, with the integration extended from 0 to oo. Later, Van der P o l and B r e m n e r went deeply into it symbolic calculus based upon the two-sided Laplace integral (integration from -^* to -; ). - The space available does not permit it.-; into details regarding other mathematical work in connection with radio and acoustics. We can only refer to the numerous publications by Struts on acoustic and antenna problems, Niessen's calculations on aerials and cavity resonators, C. J. 13 o u tv k a nt p's work on radiation properties of antennae and acoustic and electromagnetic diffrac- tion problems, that of F. 11. L. M. Stunipers Philip>-Millrr tape (upper picture) in which a sound track (10 times enlarge(l) has been eut. %% lien li_111 passes through the tape a diffraction sprctunl is obtained (lower picture) from which the Fourier analysis of the recorded sound can be read. lit thi? cast- (sinu-oidal signal) the speeLrunt consists only of components of the zero and first orders. and Th. .1. t\ cv-crs oil frecluenc~- modulation, 'I'e II e gens studies of network synthesis. from which the .gyrator" subsequently appeared as a new netiyork element. and finally Kieynen's investiga- tions of electric fields in radio valves, etc. As regards m athetnatical and theoretical-physical contributions outside the realm of radio, reference is to be made to the investigations of J. Ilaringx into problems of applied mechanics, the publications by Bouma and C. Ilcllcr on the geometry of colour space, and those by Niesscn on ditnagne- tism and by Verwcy and J. Th. G. Overbeck on the theory of lyophobic colloids. Approved For Release 1999/09/24: CIA-RDP83-00423R002000130013-1 Approved For Release 1999/09/24: CIA-RDP83-00423R002000130013-1 In the foregoing section an attempt has been made to give a review of the scientific research work undertaken in the period 1923-1940, and incidentally mention has been made of the technical products that emanated from that work. The development of this research suffered a check when on May 10th 1940 enemy forces in- A 1930 air-raid warnings, etc., all tended to create an atmo- sphere adversely affecting work. It would be wrong to suppose, however, that scientific research was thereby brought more or less to a standstill. On the contrary, manyinvestigations not directly concerned with practical applications were widened in scope and in some fields important results were reached, M 0 10 20 30 40 50m Ground plan of the Physical Research Laboratory as it has been since 1942. A high- tension room., B material-testing department, C television studio, D horticultural glass- house, E small greenhouses with artificial climate, F one of the chemical departments, G one of the battery rooms, II library, I installation for carrier telephony, J engine room, K glass-blowing shop, L central workshop, M room for testing transmitting valves. The wing K-L-M adjoins the main diagram at a-a on the right. Most of the buildings have either one or two upper storeys. vaded the Netherlands and shortly afterwards Eindhoven and the Philips' works came under military occupation. It is not the place here to enlarge upon the course of affairs during the period of occupation, which, as far as Eindhoven was concerned, lasted until September 1944. As everyone will realize, the state of tension arising from war conditions and the frequent acts of injustice, coupled with more direct causes such as scarcity of foodstuffs, clothing and means of transportation (bicycle tyres), and further a number of air attacks on the works, repeated though care was taken to keep them secret from the occupying forces. The long working hours imposed by the enemy administrators were further turned to use for the exchange of experiences in all sorts of domains by organizing lectures, courses of instruction, etc. After the liberation of Eindhoven in 1944 it took some time before a return to normal conditions could be established. In the first half of 1945 the northern half of the country was still in enemy occu- pation and even after its liberation there was no regular contact with the rest of the country owing Approved For Release 1999/09/24: CIA-RDP83-00423R002000130013-1 CRYRnul I Approved For Release 1999/09/24: CIA-RDP83-00423R002000130013-1 to the lack of railway communications. In order to help university students. ti%Itlt permission of the government in February 1913 a temporary- academy was set up at E,indhoven where it large number of Philips' scientists assumed slue role of professor, and this continued up to November 191.5. In this connection it may? be well to point out that relations between the Philips laboratory- and the higher educational authorities have never been confined to that special occasion. Long before that there had developed in the course of time it more tricted. The publication of Philips Technical Review, begun in 1936, had to be stopped in 1942, and publications in the Dutch journal "Physica" could only be made in the native language. It was not until 1946 that journals and books began to come into the country again from abroad. On 1st January 19.16 Philips Technical Review appeared again. Meanwhile, in October 1945, the first number had been issued of it new publication under the name of Philips Research Reports, containing scientific articles which bear a decidedly Department for analytical chemistry in the new part of the Physical Research Laboratory (1950). pYR -fie intimate relationship between the labora- Philips character or which owing to their volume is e elsewhere. Furthermore part of the material suitable for publication which University at Delft, partly on account of the fact that quite a number of scientists have in had been collected during the years 1940 to 1945 course of time left our laboratory to take up a was published in book form. professorship. Meanwhile the aced of more space was being felt During the occupation one began to feel more and in the laboratory, which in 1929 had already under- more the lack of literature from the outside world, gone a considerable expansion increasing ten-fold so that as far as scientific work was concerned the amount of floor space originally had the feeling of living as it were in a vacuum. The possibility of publishing was also greatly res- in 1923. A new wing had already been built in 1942, for the administrative staff and the library, but Approved For Release 1999/09/24: CIA-RDP83-00423R002000130013-1 Approved For Release 1999/09/24: CIA-RDP83-00423R002000130013-1 until 1945 the latter had been housed elsewhere owing to the risk of fire due to air attacks. In 1950 a second floor was built onto the oldest single-storey part of the laboratory first erected in 1922, and that new floor was destined mainly for chemical work. In 1946 a change was made in the management of the laboratory, Prof. Hoist, whose 25th year of directorship had been celebrated in the laboratory in 1939, retired from that function. As adviser to the concern, he has still at the present day a word to say, be it indirectly, in the course of affairs, whilst at the same time he is devoting himself to the interests of the Technical University at Delft, where he holds of the Presidency of the Board of Governors. The direct management of the Philips laboratory was placed in the hands of a triumvirate formed by the physicist Prof. Dr. H. B. G. Casimir, the electrotechnician Jr. II. Rinia and the chemist Dr. E. J. W. Verwey. For reasons which will be understood, in this section it will not be possible to do full justice to all the research work which has been undertaken in the Philips laboratory in the course of the last decennium and which, in part, is still in progress. Neither will it be possible to mention the names of all those engaged in the various investigations in the laboratory. More so than in the preceding sections, here atten- tion will be paid to materials and products and their applications. It has been seen that in the period 1923-1940 scientific interest was directed for a large part towards gases, particularly as carriers of electric discharges. In addition, in various ways more and more interest came to be taken in solids. Mention has already been made of the investigation of thin crystal layers adsorbing foreign atoms. Activity in the field of radio demanded a closer study of the dielectric properties of glass and other insulators. For illumination engineering, too, glass had become an important material, as a result of the demand, for instance, for ultraviolet-transmitting glass and for intermediate glasses for combining glass with quartz glass. For the fusing of glass to metal suitable kinds of glass and alloys were required. In the tech- nique of lighting fluorescent substances came to be applied more and more, so that the phenomenon of luminescence had likewise to be studied in the laboratory. Further, attention has also been drawn to magnetic materials, such as magnet steels and ferrites. Generally speaking it may be said that round about 1940 interest was centred upon solids and the problems relating to the solid state, both from the point of view of purely scientific investigations and in respect of practical applications. In the follow- ing a number of materials will be briefly dealt with, but since it will be mainly the results that will be brought forward it is well to point out once more that in many cases these results are due for a large part to purely scientific research. As an example may be mentioned the investigations into "induced valency", which led to improved methods of preparing semi-conductors and luminescent materi- als, and the insight gained into the structure of "sp i n e l s", which resulted in a greater variety of "Fcrroxcube" products. Luminescent substances The investigation of luminescent substances begun about 1935 led not only to the results already mentioned but also to a wider knowledge of lumines- cent tungstates and molybdates and of some acti- vators such as Mn, Ti and U in different states of ionization. Of particular practical importance were the silicates activated with Ti and magnesium arsenate activated with tetravelent manganese. With the latter substance, which shows a strong red fluores- c.-ncc, it is possible, for instance, to improve con- siderably the colour of the light from the small high-pressure quartz mercury lamps. The investigation of sulphides gave a better insight into the part played by "fluxes", such as NaC1, used in the preparation of luminescent sub- stances. It appeared that it is the Cl--ions that make it possible, for instance, for monovalent Cu"F-ions to be "built into" the lattice. The same can be reached by introducing into the lattice, which consists normally of bivalent ions Zn++ and S--, trivalent cations such as Als+. Results were also achieved in respect to lumines- cence brought about by bombardment with cathode rays; a deeper insight was gained into the phenome- non of saturation with increasing current. For some purposes, such as radar, it is not the fluorescence but rather the phosphorescence (per- sistent after-glow) that is of importance. It was found possible to obtain a fluorescent screen with long persistence by making it in two layers, the first of which gives a blue fluorescence under the influence of the cathode rays, this blue fluorescence then being suitable for producing a green phosphorescence in the second layer. For other purposes, such as the televising of films, Approved For Release 1999/09/24: CIA-RDP83-00423R002000130013-1 Approved For Release 1999/09/24: CIA-RDP83-00423R002000130013-1 substances with it short persistence are desired: a "field" produced on the fluorescent screen by an unm.odulated electron beans is itnageel onto the, film, whilst behind the film is a photocell. This converts the light passed through, which. is modu. lated by the variations in density of the film, into it signal which is passed to the transmitter. ceramic materials (ferrite s). because these have proved to he of great importance for high-frequency technique (radio and telecommunications). Of theoretical importance was the interpretation of the losses which the magnetic ferrites show at very high frequencies (105 to 107 cjs): these losses were ascribed to the gyromagnetic effect A simple hydrogen liquefar1or has Lrcn con,trueted for the examination of solids at low temperature (21) 'K). The hydrogen gas is fed in under high pressure and prrrooled to the temperature of liquid nitrogen, after which, through expansion, by employing heat exchangers according to the Linde method, it becomes partly liquid (Joule-Kclcin effect). This installation has an output of about 2 litres liquid hydrogen per hour. Many other important applications of lutnine.s- cent substances which have been investigated in the laboratory have to be passed over here. Ceramic materials and glass Ceramic materials are obtained by sintering together small particles which in themselves have a crystalline structure. We do not refer Mere to the more common materials like porcelain. steatite. etc., about which little research work has been clone. but to special materials, as for instance those with a high dielectric constant, such as rutile (TiO.,), and titanates such as 13aTiO.{. With which important work has been done in recent. years. Particular mention is to be made of the magnetic prophesied by Landau, and this conception was confirmed experimentally. Of practical importance was the resultant know- ledge gained of the fact that the less the initial permeability of the substance in the low-frequency range, and thus the greater its crystal anisotropy, the higher is the frequency at which the gyromag- netic losses become perceptible. The terrific materials. which combine great hardness and relatively light weight with a very small electric conductivity and favourable magnetic properties. such as low losses in a wide frequency range, are now being manufactured by Philips under the name of "Ferroxcube" in various compo- sitions. Approved For Release 1999/09/24: CIA-RDP83-00423R002000130013-1 C.PyRnwl Approved For Release 1999/09/24: CIA-RDP83-00423R002000130013-1 In addition to the ferrites, of equal importance colour or which, on the other hand, very readily are the ceramic semi-conductors, which will be change colour, and glasses which are transparent dealt with below in a separate section devoted to to ultra-violet radiation. semi-conductors. Improved quality and saving of space are important advan- tages of the magnetic material "Ferroxcube" as compared wiLh metallic magnetic materials. Left: can containing a bandpass- filter coil for carrier telephony, the core of which consists of nickel-iron wires and the jacket of dust-core material. The can is necessary on account of the small effective permeability of the dust-core material. Quality factor Q = 220 at 60 kc/s, volume 210 cm3. Right: coil with core and jacket of "Ferrox- cube", Q = 600 at 60 kc/s, volume 41, cros. Glass is a material of fundamental importance for the manufacture of incandescent lamps and radio valves. Apart from the obvious physical prop- erties, such as the softening point, coefficient of expansion and specific gravity, there are many other properties to be considered, such as the di- electric constant, dielectric losses in high-frequency electric fields, electric conductivity, spectral trans- mission, etc. Considering the large number of in- gredients from which glass is mostly made, and consequently the numerous possible variations in composition, it would seem to be an almost impossi- ble task to gain a clear insight into the effect of the composition of a glass upon its physical proper- ties. Yet in recent times considerable success has been attained in this direction, particularly due to the better theoretical knowledge acquired as a result, i.a., of the work done by Zachariasen. It is now possible to form an idea of the internal structure of glasses and from that to predict their properties. Even though the reality proves to be more complicated than the theoretical model, the latter anyhow points the way to approximating the correct relations of the phenomena and for investigating those relations which are most prom- ising for gaining the insight desired. In cooperation with the glass works the following practical results have been obtained: soft glasses with small dielectric losses, glasses which have small dielectric losses independent of frequency, glasses which under the influence of X-rays do not dis- Metals Metals form an important and extensive group of materials. The investigation of tungsten and molybdenum and of metals like titanium, zirconium, hafnium and thorium has already been mentioned, as also that of alloys such as chrome-iron. The investigation of in a g n e t s I. c c l s has likewise already been referred to. The very important "Ticonal" (an alloy of iron, titanium, cobalt, nickel and aluminium) with a high value of the product (BII)max and great coercive strength, was further improved by making it anisotropic by cooling in a magnetic field or by some other means. The nickel-iron with anisotropic structure ob- tained by rolling, for use in loading coils, has also been mentioned elsewhere. Extensive investigations have been carried out as to the manner in which the texture of this material could be influenced by a suitable thermal and mechanical treatment. Another group of products is formed by the weld- ing rods, the coating of which has been the subject of particular study. Special mention is to be made of the new method of contact welding, for which purpose the rods are given a special coating with a high iron content. It is partly in connection with this that extensive investigations have been carried out into the dif- fusion of gases in metals. This subject had be- come of real importance as soon as the manufacture of water-cooled metal transmitting valves and metal X-ray tubes was begun, and it proved to be of particular interest in connection with welding problems, especially as regards the penetration of hydrogen into the metal of the welding bead, causing porosity, cracks and fractures. In this connection mention is also to be made of more fundamental research, as for instance that concern- ing ageing phenomena such as occur, inter alia, in welding. The absorption of gases by metals has parti- cularly also been studied in the case of metals like zirconium and titanium, which are used as getters in X-ray tubes and transmitting valves. Incidentally reference is to be made here to the coating of anodes of transmitting valves with zirconium to give them a black surface with good heat-radiating properties and also to reduce secon- dary-electron emission. Investigations of a more technical nature in the field of metals led to new methods of shaping and improved methods for Approved For Release 1999/09/24: CIA-RDP83-00423R002000130013-1 Approved For Release 1999/09/24: CIA-RDP83-00423R002000130013-1 determining the properties of samples of metal. an example of the former being the so called 6-lost wax" casting of metallic parts of instruments and apparatus which would be too costly if Lite ordinary methods of processing were followed, whilst ail example of the latter is to be found in the m i c r o- hardness meter. This section on metals will be concluded by a short reference. to investigations concerning oxi- dation and corrosion. Interesting aspects are presented by the method of hardening alloys by internal oxidation. A study of corrosion at high temperatures revealed that. small quantities of molybdenum oxide may have a harmful effect. Investigations into the non-oxidizing property at high temperatures and the solderability of non- oxidizing metals were particularly of importance in connection with the development of Llie hot-air engine. A peculiar feature of these materials is that often their specific resistivity is not a property inherent in the material, as is Lite case, for instance, with a metal, but that it depends to a large extent upon the antecedents, such as Lite temperature and till- gas atmosphere applied in Lite preparation, Lite presence or not of impurities and many other factors. In the field of oxidic semi-conductors some extensive crystal-chcu.ical investigations have led to Lite production of semi-conducting materials answering high requirements of reproducibility and stability. Such a material is being marketed in various fortes as N.T.C. "resistors" (negative tem- perature coefficient. resistors). Much attention was paid also Lo selenium. The resisttutce of selenium can be varied by the addition of foreign substances. This investigation has led to the production of rectifiers suitable for low vol- tages, e.g. 18 V, and, by connecting them in parallel, for high currents. On Lite other hand very small rectifiers are being made for currents of a few milliamperes, as used in the a.nplifving technique, for example. for modulator cells, Which play an important part in carrier-telephony, and in series- connected sInall cells for rectifying high voltages. By a certain treatment of the surface of Lite ,eletriuin and choice of Lite electrode material it is possible, to a certain extent, to determine Lite voltages which are to be applied per rectifying unit. I)iiring the years 1910-1915 there has been re- newed interest in the crvstal rectifier, a coIn- ponent used in the early days of radio. It appears that in the range of ultra-short waves, which has become of such importance, this clement in a more perfected form offers advantages over rectifying valves. Extensive investigations are proceeding in the laboratory also in this field and have already led to it rapidly increasing manufacture of various types of crystal rectifiers. There are indications that the possibilities of applications in time field of semi-conductors are not by any means exhausted, and that, by the very reason of their abnormal properties, we are only at. Lite beginning of a development of great impoM,mce for electrotechnical engineering. Between the insulators of an inorganic and an organic nature, such as glass, porcelain, amber. polystyrene, on the one hand and the metals as good conductors for electric current on the other hand, there is an important group of substances which as compared with metals show little conduc- tivity, e.g. iron oxides, copper oxide, selenium, ger- manium, etc. These are of interest because the%- possess typical properties lacking two groups. 'T'heir principal property is a large, negative. tentperaturc coefficient of their resistance, a proper- ty found in practically all representatives of this group. Sonic of theme also show photo-conductivity. in that when exposed to light their resistance is reduced. Others, when provided in a certain tisay with electrodes, appear to have rectifying proper- ties, which means to say that when Lite current flows in one direction the resistance is many tiers, say 1000 or more Limes less than in tl.c other direc- tion. There are also certain materials whose resis- tance appears to he dependent upon the electric potential gradient. Although these properties have been known for it long time it is only during the last 10 to 15 years that it has been found possible to utilize tltent. Obviously a high. temperature coefficient of the resistance ofliers many possibilities. Mention may be made, for instance, of the measuring of tempera- ture and of radiation, furthcrntore, owing to the negative sign of time coefficient, there is Lite possibili- ty of suppression of current peaks and application in delay devices, regulating apparatus, etc. This review will be concluded by referring to some products which, have particularly come into existence in Lill' last ten to fifteen years as a result of laboratory work. The reader is not to expect a catalogue with detailed descriptions. Many of the Approved For Release 1999/09/24: CIA-RDP83-00423R002000130013-1 CPYR Toved For Release 1999/09/24: CIA-RDP83-00423R002000130013-1 1.891-1951 37 products which will be mentioned have already been described more or less fully in recent volumes of this journal, whilst a description, of some others will shortly be appearing in our columns. Suffice it, therefore, to mention in a few words only the most important products. Sources of light In the field of lighting we have already referred to the "TL" lamps, which as such have already Further, there is the low-pressure mercury lamp without any fluorescent material but made with a glass which is transparent to ultra-violet radiation (2537 A), viz. the so-called germicidal lamp. Other special sources of light are the flashlamp for the illumination of Wilson chambers and for other photographic instantaneous exposures, and a point source of light in the form of a gas-discharge lamp the light of which can be modulated up to high frequencies. long passed the laboratory stage of development. Further investigations in connection with these lamps are being carried out in regard to their colour rendering, for instance with new phosphors used in their manufacture. Particular mention is to be made of the application of "TL" lamps for irra- diating plants. Since 1949 the Philips laboratory has had a large horticultural glasshouse at its dis- posal, in which various plants are being cultivated, and also a dozen smaller glasshouses illuminated exclusively with artificial light. With the large variety of phosphors available it is possible to investigate how the growth and flowering of plants are affected by the spectral energy distribution and the intensity and duration of radiation. Radio, television, etc. In the field of radio conditions had already reached such a stable state before 1940 that the normal development of valves and apparatus no longer belonged to the work of the laboratory, so that attention could be directed towards new develop- ments. In the first place mention is to be made of the new valves for ultra-short waves (decimetric and centimetric waves). Development of these valves had already reached an advanced stage abroad during the war years, so that in 1945 Philips had a great deal to catch up with. Extensive investi- gations had already been carried out with radio valves in the metric wave range. Special tubes were developed based upon the velocity modulation of Approved For Release 1999/09/24: CIA-RDP83-00423R002000130013-1 CPYRGHT Approved For Release 1999/09/24: CIA-RDP83-00423R002000130013-1 Cucumbers cultivated entirely under artificial light. The light is supplied by "Ti" ,lamps. The temperature inside is prevented from rising too high by causing tap water to flow down the pane of glass in front of the lamps. Half-way down between the "T1' lamps is a TIN lamp, the ultra-violet radiation from which prevents the growth of algae on the glass. ,lcctrons (the velocity-modulation valve, the dysiron, the multireflection tube), employing a umber of Philips' own inventions. An important improvement of heated. cathodes s Lite L -cathode, which contains a reservoir illed with barium oxide and enclosed by a porous Tall of tungsten acting as the source of electron mission. With the aid of this cathode a disc-seal n o d e can be built for wavelengths down to 8 cm frith a clearance of only 40 !. between cathode and grid. This new type of cathode offers important possibilities for many other applications as well. An intensive study is being made of Lite special circuits for generating ultra-short waves, by em- ploying cavity resonators, and of modern means for conducting high-frequency energy with Lite aid of wave guides. After 1945 the development of television had to be taken in hand again in the laboratory on account of the greater interest being shown in it everywhere. Approved For Release 1999/09/24: CIA-RDP83-00423R002000130013-1 1 . YID'' , r I I Approved For Release 1999/09/24: CIA-RDP83-00423R002000130013-1 JULY-AUGUST 1951 1891-1951 Tubes for centimeLric waves. 1~'ront left to right: a multi reflection tube with a contin- uous output of 20 W on a wavelength of 12 cm; a receiving tube. of the "lighthouse" shape for amplification of wide frequency bands (gain 10 at a bandwidth of 50 Mc/s, noise figure 10 dh at a wavelength of 10 cm); a magnetron yielding pulses of 1000 kW at a wavelength of 3 cm; a velocity-modulation valve with a continuous output of 100 W at a wavelength of 3 cm. At first a system of 567 lines was used, with 25 frames it could quickly be changed over to different num- per second. In the audio channel frequency hers of lines. This proved to be of great value for modulation was applied. As a result of many judging the relative merits of various systems. discussions on the question of the number of lines When, later on, the Netherlands Television Commit- the transmitting apparatus was designed so that tee advised the adoption of a system with 625 lines 67074 Some 1, cathodes (with a cigarette for comparison of size). The L cathode has a porous, metal, emitting surface and can withstand heavy loads, say 1.00 A per em2. Approved For Release 1999/09/24: CIA-RDP83-00423R002000130013-1 Approved For Release 1999/09/24: CIA-RDP83-00423R002000130013-1 .'It't-utt fin takiti_ inra -ur.?tnrnt - of it , (.It,( it% - mmItil it tiit t c al%r (oil thr IxIre it (- right) at a ?a,~ lrti_tII ut 3 rni. Ilrrr ?a%r ,Inuit'. are ti-rd fur runtlurting tilt' energy. and ?.i franc- Itrr -round Hit- irt-tallatinn %%a- ^ladr -uitahlr fur that Furthrr. at.trutiurt N% a, dt?cutrd hut It Iu thr ltruhlrnr- rurunntrrrd at tltr rrcri\ i11 , 11111 and to t.hu-t ari-in_ in the trap-nti--ion. 1- far a- rrcrlttiuu i; runt?t?rnt?tl. ha-rd 111tun flit- rt?~ult. of rsltrrintrnt- alrt?atl,, nu?ntiuurtl a -v-trim (d projection ti-N-N 1-1(111 v, a-',, urkrtl out \cillt the aid of' a `+rIt tit it!t ultliral -v-tt?rn. a-irtg vrrc -tnall ltrujt-rtion tubes with tilt -rrrrn coated No, ith ltho-lthur- suitable For tin }turbo-r. tiltt-t?ial ltrrrautions hall to be taken main-l di-coloratiuu (if' tht? gla,, of thrrr tuhri unti l the influrucr of cathode ratis ant! S-ravs. In the ulttit?al -v-lrrn Itruln?r. n-r vVa- tttatlr? of a correction I' I a t r made of gelatin. fur ocitich a -eltarate method of ruanufacture had Lo hr tlrvelojtrd. I.rft: t?, I-i.,k-nli IIII1r- lur t,-leti.inn (an irrinu-nlir anti an iIII tgt' Ii i_It t: it Ii i r t it rr t it Itr tnr ttrujr?rtion tclr, i-inc Apprnvnrl I r%r Rnlnncn I QQQIf1Q/9A ? (1 A_Rr1DR4_fflA94RfG9=013013.4 ^"t CPYRGHT Approved For Release 1999/09/24: CIA-RDP83-00423R002000130013-1 Of course attention had also to be paid to direct- view reception. One of the most important results of the work done in this connection was a consider- able improvement in regard to flicker of the image by employing phosphors having a long persistence. As regards TV transmission the most important advance made was in the construction of new pick-up tubes based on the principle of the image iconoseope. Further improvements lay in the television cameras and in the studio lighting. Except for some short interruptions there have been regular experimental television transmissions from Eindhoven ever since 1946, for which purpose a studio, a control room and dressing rooms for artists were fitted out in the laboratory building. These experimental transmissions have helped much towards arousing the interest now being shown in this youngest branch of technical develop- ment both in the Netherlands and in adjoining countries. Next in order to radio and television is the work done in the field of telecommunications. Ever since 1935 there has existed a department in the laboratory (organically not belonging to it but as part of the A.F. telephony department of the works) where apparatus for carrier telephony, i.a. a 17-channel system, and for A.F. telegraphy have been developed. About 1940, in cooperation with the laboratory, a modern carrier-telephony system for 48 channels was developed, in which the new core material for coils, "Ferroxcube", plays an important part. This system is already being used on an extensive scale in the Netherlands and in Switzerland, whilst it is to be installed also in Denmark in the near future. In this connection a word of grateful recognition is due to the Netherlands P.T.T. officials for their close cooperation. In 1945 the carrier- wave department was transferred from Eindhoven to the Philips' Telecommuni- cation Industry at Hilversum, whilst a research group for telecommunications was established in the laboratory. Development work in Ililversuni is proceeding further in the direction of the improvement and reduction in size of electrical and mechanical parts, with the aid of results reached in the laboratory. Special carrier systems have been developed which are suitable also for short distances. Further, by developing through-filter and other filters, the laboratory has already contributed much towards a system now in course of development at Hilversum for incorporating some hundreds of channels in a coaxial cable. In this laboratory work is continuing on new methods of modulation; for instance, a simplified form of pulse-code modulation has been studied, the quantum modulation, which makes it possible for conversations to be carried satisfactorily over long distances in spite of a high noise level. In addition, the possibilities of applying new materials and components for telecommunication apparatus are being studied. In this connection mention is to be made of the new switching tubes with ribbon-shaped electron beam, which promise interesting applications in the field of telecommunications and electric computers. Special mention is to be made of the system of facsimile transmission worked outinthe labora- tory, by means or which documents can be transmit- ted and photographically recorded at the rate of 5000 cm2/minute. Of importance for meteorology is a newly devel- oped radio sonde, in which extremely small radio valves with low current consumption are employed and with which experiments are now being carried out in conjunction with the Royal Netherlands Meteorological Institute at Dc Bilt. such things as repeaters, a super-group Dr. A.F. Philips in front of the camera of the Eindhoven television transmitter. Approved For Release 1999/09/24: CIA-RDP83-00423R002000130013-1 Approved For Release 1999/09/24: CIA-RDP83-00423R002000130013-1 A product w- IIicI I certainh ha- -onto crrnnr'ctiun the lri-tun of une cdinder i- caused to act as Hie with ra(lio. ennridcrinr the jived of it ul)ltly -ourcc tran-iu r 1u-tort for another. i- of intltortancc in in place- w hcrc no rdcciricitv i- av ailahlt.. but which cortnectiort with 1nture lro--ihilitie- tin' curt-etluencs~s represent- the outconu? of a dctcinluncnt of it- uf' which ran utt Net. he falh predicted. own. i- tlic air eit t;irtc already rcfcrrcrl to in thi - rcview. From it clo-c -1nth of the kcal e chan~?,. hetssecn flowing ga-e- anti metallic wall- and of utatcrial- - uitalde I herefor. arid further of, the therrno-d, nantic- of tlo-v-\ r1r. it ha- ltccontc lto--ihlc to build a li ht hint--peed rnttur with frond tIli- anal efficienct. 1 to ws principlc_ ufapplicatioufor-~-tcnt- with more titan one c,,lindr?r_ according; to Ntiltich III the lield of acuu-tics there are rloite a numLer of ncvti product - in he no - ntionerl. F it-t of all late itn- lrrolcti -ountl rclrrvolut?tinrt by tuean- of' -tereu- I'lrons. \tihich ha- led aLu to the curt-trrtctiort of ,mill nrierolrhone-. The ideal nicrophune.witlt -mall dintco-ions compared vcilh the vrtv-clcniZth. al.o for iti`h audio-frcrlut?ncie appeared to he nut-t clo-eh apprurimatcd by the coudcit -cr uticJ. ophune Approved For Release 1999/09/24: CIA-RDP83-00423R002000130013-1 Approved For Release 1999/09/24: CIA-RDP83-00423R002000130013-1 Taking measurements in the testing of an experimental air engine. Energy input by electric heating, energy output via a loaded dynamo. Connected to the desk on the left are therrno couples measuring the temperature at various points (inside and outside). A Farrthoro pressure indicator records the pressure in the cylinder as a function of time; the phase of this diagram is checked with the aid of a capacitive pressure indicator (con- nected to an oscillograph) and a stroboscope. Hall for acoustical investigations (i.a. stereophony) and large-screen television (almost 3 m X 4 m). Approved For Release 1999/09/24: CIA-RDP83-00423R002000130013-1 Approved For Release 1999/09/24: CIA-RDP83-00423R002000130013-1 which can Hutt be rood' Ili it size of' about 20 ruin. and for special purpust- ex-en as small it- T min. In Lhe Philip- laboratory the nett'--art attestion has also iccn paid to the dctrloprtrcut. -tartttl in Denmark. of the nta g rt e t o p h o nt for recording and reproducing -ound. Thi- tttltloprn?ut ohligtd the manufacturer- of gr:nophonc record, at last to relintlui-h tlo? tb?nrand that it -built{ be po-sihle to play their record- both elctLricahIv and mtchanit- audibility. Icd further to tic designing of a vector cardiograph. some specimens of which have hecn gittu to nu?dical experts for testing. 1no01g the i-rav tilts titre is it net, one for contact tit(-rapt and. further. note high-powered Iuhc- for \ - rat (Ii fir action with accessorv apparatus. ally. as it rt=ult of tshu It to j. intprot ernenI.- hetame po"iilc in the fit-ill oftltttrital gramophone reproduction It,. urtau- of ntirrourroot t rctord