PHYSICS

• Document Type: CREST
• Collection: General CIA Records
• Document Number (FOIA) /ESDN (CREST): CIA-RDP80-00809A000600210082-8
• Release Decision: RIPPUB
• Original Classification: C
• Document Page Count: 13
• Document Creation Date: December 22, 2016
• Document Release Date: June 23, 2011
• Sequence Number: 82
• Publication Date: January 18, 1949
• Content Type: REPORT

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PBOT CK= A>I> I WYR's Al AJITDMJIiT-
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Submitted 28 Aapmst 1947
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for daily me.
its priaeipie of maltiple s+lifioatica b,7 assns of sescmdar7-sleotroa
aolaoicm has as its basis the oamstrnotim A himbli asasit ve aaltiplier In-
4 is sash as the easbinatim of photsleetrioa117 ao+ire oetboam alto
effostive snifters, whose astim sassnts ?o asplifjing'As esth'4.a photo-
esrasmt. The positive rtsalts obtoiasd reasntly (3,4,5) In t07Sm
ph.tosleetbon aaltiplisrs In spse'ran analysis and astrasm p attraot$1 She
attmmltim of any swearoh voehsrs, mad ~17 revived the interest in phvto-
elssram aaltipliees.
CLA:. .-CATION CO1'3A:.
CENTRAL IN MV h REPORT
INFOR ffffl
FOREIGN DOCUMENTS OR RADIO BROADCASTS CD NO.
COUNTRY ussa
SUBJECT Pbisics
HOW
PUBLISHED 10104tbl7 psriodieal
WHERE
PUBLISHED
DATE
PUBLISHED dsnaaa7.1948
LANGUAGE Rnrpien
I. L C.. 81 M2 U. A@ "INSW M'}Y0M1oYO. w m0 anoawaow.
M els CICtgw M 1,t wIn 18 La ,LMt1 I .. hRwse IC PCI,
r4xtR, YU. 5110101101 w v,m Pon a sea1"1110s.
DATE OF
INFORMATION 1947
DATE DIST.I8 dsmhae7 1949
SUPPLEMENT TO
REPORT NO.
SOURCE Vnr=l T eeisheskar 71miki, To31. ZYIII, No 1, 1948. (]'b8 Per Abe
41490 -- Trans tiro wpboifioall7 requested.)
50X1-HUM
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(ONFP,
In the multistage secondary-electron multiplier in a glass envelope
and elbotromagnetic focusing suggested by KubeLskiy, a oanplicated Ag-O-Ce
layer was employed as a cathode, and a Cu-S-Cs-layer as an emitter in cascades.
These layers were unresponsive to temperature changes and were efficient in
respect to secondary-electron emission. In this type of multiplier (with
13 stages) with a total applied voltage of 750, an~ lifioation of 103 is
obtained, which provides speotroseneitivity of 1-3 A/lm (amperes/lumens).
The dark current of multipliers with given parameters varies from one
type to another within the limits of 10-6 to 10-! A. Itmy be considered
an established fact that the basic cause of dark current in an multiplier
is the thermionio emission which can be considerably decreased by in-
creasing the operating output or by cooling the cathode (8,9).
The magnitudes of the speotrosensitivity and the dark current, as is
well know determine the threshold sensitivity of the multiplier, (The
term threshold sensitivity means the point at which the light stream pro-
dunes a flux equal to the dark current. In fact, the threshold sensitivity
is determined ::y fluctuations of the dark current.) In striving to improve ",
the parameters of a photoelectron multiplier, 1. e., to lower its threshold
sensitivity, an antimony-cesium cathode was tabstituted for the Ag-A-Ce
cathode. Among the qualities of the antimony-cesium cathode area .nigh
speetrosensitivity in the visible part of the spectrum (10,11), large quantum
output (12,13), and resistance to changes of temperature, as well an a low
vain, of dark current (14), and high durability. There is no apparent
possibility of combining a Cu-S-Ca emitter and an antimony-cesium cathode
since, according to literature on this subject, the presence of traces of
sulfur greatly lovers the sensttititj of the latter (15).
However, as a result of the work undertaken, as may be seen below, a
technological method was worked out which guaranteed the production of a
sensitive cathode with a Cu-S-Ce emitter containing sulfur.
Research Procedure
The procedure in obtaining secondary-electron multipliers (having an
antimony-cesium cathode) with a glass envelope consisted mainly of the
following stages:
1. Application, by chemical cooling and electrolysis, of a layer of
miller On Ws inner wall of a glass tube. The silver layer served as a
lining for the On-S-Cs emitter and made contact with 15 platinum lead-ins
soldered into the glass. As a result of the deoxidizing reaction, the silver
was oeparated into:
Z,(Ka( ) 7 O3+C6H12o6 = C6H1207+ 4IH3+ H2O+2Ag.
2. Zleotro:y"io application of a layer of copper and treatment with
hydrogen sulfide. Due to the action ofthb sulfur, a layer of cuprous sulfide
was f;+' se on the copper. The reaction, as is well known, takes place in
two, was n
Cn2t+} . Cu28+H20,
2Cn}H2S+ 2 Cc28+320.
). Scaling the antimony atomiser in the tube a4d degasaing the tube in
a vacena apparatus nsder conditions similar 'a the well-known msthod of pre
paring a layer of Dhotoeleegnt on glass.
4. Application of a local layer of antiaw4y to the glass near the first
stags by vaporisation of an antimony ball, screened from the window-side of
the multiplier, in a high vacuum (10'6 ma). The opaque layer of intimacy
produced in this manner has a metallic luster. To obtain simple antimony-
cesium cathodes, the surface of the glass is cooled by an air current during
the process of coating with antimony.
(ONFmffi f*
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 Sanitized Copy Approved for Release 2011/06/24: CIA-RDP80-00809A000600210082-8
CONFIDENTIAL
The layers (of antimony and cuprous sulfide) are activated at a ten-
perature of 2100 C with cesium vapor which is introduced through a glass
bulb connected at the anode aide of the tube. The cesium is obtained by
heating a nickel each filled with a mixture of C?CL+ Ca in a high-frequency
oven. The activating process is controlled by taking psriodio measurements
using a "guard ring," of the cathode photocarrent and "leaks" (interstage
conductivity) between the cathode and the first stage. The source of
light is provided by an incandescent imp (6 - 8 volts) fastened to the
cathode of the tube, which is excited only at the moment when measurements
of the photoeurrent are; made.
Activating Procedure
The properties of the inspected cathode changes according to the de-
gree of the absorption of the cesium by the antimony layer. This is evi-
dent in the changes of the photocurrent and thermoelectric current in time.
When the point of mnximam behsitivity is reached, the layer takes on a
dark red color as the light is passed through, during which the photo-
emission remains for some time at a constant maximum magnitude. At this
point the oven is switched off, the bulb with the excess cesium unsoldered
and, if there are no large "Leaks" in. the last stages, the secondary-
electron multiplier is unsoldered.
The thermal emission of the antimony-cesium cathode at this tempera-
ture (210?0) is small, approximately 60 - 80 times lose than for an oeeiua-
ozide cathode. For this reason, in contrast with the cesium-oxide cathode,
whore thermal emission at the given temperature is sufficiently large, we
were obliged, in obtaining antimony-cesium cathodes, to control the acti-
vating process from the standpoint of photocarrent and not thermoelectric
emission.
The well-known fact (16) of the dependence of photosensitivity on the
temperature of an antimony-cesium cathode demandeu attention. The photo-
sensi''vity of the cathode increased in proportion to its cooling from
210 C to room temperature. At room temperature the photosensitivity was
two to three times greater than at 2100 C.
One very interesting result was that at a given temperature, the
coppor-sulfide layer in the oaccades was also aotivated by the secondary-
electron emission sloultaneaicly with the activation of the cathode. This
ooadition, and also the absence of an intermediate stage of oxidation and
partial deoxidation, simplified the technological method of obtaining a
photoelsotron multiplier in which the Ag-O-Cs cathode in it is replaced by
antimony-teem, cathode which surpasses the AS-0-0s only in respect to
sensitivity in the red and infrured bawds of the spectrum. Multipliers
with an antimony-cesium cathode, obtained by the method mentioned, were
invaatigated from the standpoint of the photoelectric properties of the
cathode and the secondary-electron emission properties of the emitters
is casoade.
Zteosemsitivitt of the Cathode
Ilse.saromont of the absolute photosensitivity is carried out b'
illasioating a point (1 eq cm) on the surface of the cathode by an-
decomposed Light (2.6 z 10-2 lm) from an incandescent lamp with Tc e
2,8h80 K. As shown by Table 1, the photosensitivity of the cathode in
multipliers varies between the limits of 50 and 125,+/!4x. According to
Glover and Janes (17), the photosensitivity of an antimony-cesium cathode
to daylight is approximately two - two and one-half times greater than the
photosensitivity to the light of an incandescent lamp with To , 2,6480 K.
CONFJiJENTIAL
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CONFAD
No of Multipliers Sensitivity of
(test series) Cathode (lnO?cA/ls!-
h 68
9-i
i
knoMp, can be greatly increased by surface o9cidatlon with csygm as at low
is n s sufficient which can be done s practice without och difficulty. It
eienent t t to state that M IZ, using this method in serial production ob-
talnsd entisany-cesium photosleaents with a sensitivity of 125,,1 A/Ion or bettpx.
However, the speotrosemsitivity curve of high sensitive photoelements
differs from that of standard antics -Gesium photoeleaents; the nazis ofv
sensitivity and the rod limit are displaced toward the log-wave lengths,
which results, as easy be seen from Sommer I s work (13)' from the decrease In
the operating efficiency due to the oxidation of absorbed cesium ataaa.
This is olio comtirsad by the increase in thermionic emission. Ion this
reason we were obliged, for the time being, to give up the idea of Increasing
the sensitivity, because, otherwise.the gain of two or awe time in the
zpootrosemsitivity would entail, as will be evident later, the Increase in
the photoelectron multiplier of the dark current which in effect is thearw.
esilasfs+es 1' , rfeCdr:6. ot, hd 4wrktr 'catdaticselould affect the secondary-
electron properties of Cu-S-Cs emitters in cascade.
decandarr-Aectron Enissian of a Cu-B-Cs Tearer
With a view to clarifying the secondary-electron properties of the
.sitter In a photoelectranic multiplier, meacureaents of the coefficients
of oaocodary-eleott.an emission g- of a Cu-Sc+Ca layer in all stages were
made by a yisple method. The essence of the method c nsisted In taking
sianlteneoas measurement of three adjacent stages which were placed under
voltage. The initial electrons were photoelectrons, originating as a rosult
of illuminating one of the cascades by a narrow pencil of white light
(sensitivity of the on-i-cs layer 2 -
For this purpose, in the process of plotting the curve of the emitter,
an aperture 2 ma wide is left along the whole length. Photoelectra!s, moving
in an electric field, are focused by an external aeg