CONTRACT NO. RD-33

• Document Type: CREST
• Collection: General CIA Records
• Document Number (FOIA) /ESDN (CREST): CIA-RDP78-03424A002000030011-6
• Release Decision: RIPPUB
• Original Classification: S
• Document Page Count: 12
• Document Creation Date: December 22, 2016
• Document Release Date: September 15, 2011
• Sequence Number: 11
• Publication Date: May 3, 1960
• Content Type: MEMO

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~~=t, t~ ru-a.
~-~eeti Cantraet !b. ID-33
ite are ploaeed to onoloeo tro copio? of a peepoeal is rotpmso to
Toter lector dated April. 14, 1960. In the o~es-t Tou roald rich w
to ruA~rtala the paro~ras, ?e gill be pleased to do eo ae a eoet-
pise-ris~d-tie tank order to onr bait ag:waent rith Too.
ti1o ass aUo retnrnin ~, ae Ton req~teeted, Tope April 14th lottee
and all attaahasnte. It Tea I~avo ay ge.eetiow abov~t ov prepeeal,
p]eare io not Hesitate to aeataet ttie s4derei~ned.
9erT trW Tom,
JVtel
Z eooU (pr~e~oael)
! epei? (altaobrnt~e)
CQN~IDENTIAL
ONFID-Ef?~~~ ~ ;
Myr 3, 190
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vylV~IUCIV I If-iL.
In regards to items (a) and (b) the following is a description of a
proposed design of magnetic field and clamp-on current sensors for low
frequency signals. Both types of sensors utilize the Hall effect in
intermetallic semiconductors. Alow-frequency magnetic-field sensor
has been designed, capable of detecting fields below one microgauss.l, 2
As a result of this work, a magnetic -field sensor can be designed
for frequencies down to 5 cps. This lower limit of frequency is due to
the fact that a direct biasing current is used and the ohmic drop at the
Hall terminals is blocked by a capacitor. Increasing the capacitor should
reduce the lower frequency limit; however, the increase of excess noise
in the amplifier reduces the sensitivity of the sensor. If an alternating
biasing current is used instead, the Hall-output potential is shifted in
frequency and can be amplified mare conveniently. Using a regular enve-
lope detector should restore the waveform of the original magnetic -field
being measured. Although it seems that the use of alternating bias cur-
rent should enable a similar measure of direct magnetic fields, it should
be pointed out that because of the unusually high requirement on stability
of the aV?pphed alternating current bias, the sensitivit~r of the steady
magnetic -field measurement i~minished by a few orders of magnitude.
This is because the relative change in the amplitude of the bias current
causes a similar change in the Hall-output signal, as far as alternating
magnetic fields are concerned, while for the case of the direct magnetic
fields, such a change may be larger than the measured signal itself.
1 Epstein, M. and Schulz, R. B., `'Magnetic-Field Pickup far Low-
Frequency Radio -Interference Measuring Sets", 1959 IRE National
Convention Record; p. 64.
2 Epstein, M. , Greenstein, L. J. and Sachs, H. M. , "Principles and
Applications of Hall-Effect Devices't, Proc. National Electronics. Gon-
ference, Vol. 15, 1959; p. 241. ,,.. ,
~~1'~~~i~~NTIA`I`~
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The magnetic-field measurement capability of aHall-effect device
can be used conveniently to measure currents in a conductor. The method
of measuring the. magnetic field around acurrent-carrying conductor has
been utilized in the case of alternating currents using current trans -
formers. The unique quality of the Hall effect to detect magnetic fields,
both steady and alternating, is the basis for a so-called "clamp-on"
ammeter. The sensitivity of such a device. can be obtained as follows..
Let us ,assume a specimen of indium antimonide one thousandth of
an inch thick. The semiconductor wafer is then placed in a gap of a toroid
made of permeable material with relative. permeability of 850. It is con-
venient to define an equivalent air -gap which is equal to the length of the
actual air-gap plus the circumference of the toroid divided by the relative
permeability. Therefore, the length of the equivalent air-gap, for a
toroid one inch in diameter, is given by
deg = 0.001 + ~~ = 0.0137 inch.
Designating m as the current to be measured, the magnetic flux density
in the air -gap is given by
I 4~ x IO-7 I
B - ?~._ ,. ?, ~ ., __ ., r .n , ? - = 3 . b x I O -3 Im `vim .
From the work performed at the Foundation, for n-type indium
antimonide with 1016 carrier concentration at liquid introgen, it can be
assumed that a biasing current of at least 0.25 amperes can be safely
passed through a specimen one mil thick. The Hall coefficient, for this
3
material, has been found to be RH = 2.3 x 10 -Coulomb' Hence, the
Hall-output potential is given by
RH Z.3x10-4x 0.25x3.bx10-3I
t _ 0.OO1x2.54x10
CONFIDENTIAt2 -
=8.15x1013 lm volts.
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.? .
Therefore, the sensitivity can be defined as
S=~=8.15x10-3 amtere'
m p
Low input-impedance amplifiers. are available to match the low
resistance of the Hall-effect sensor, which are capable of measuring
signals down to the thermal noise at its input. Ass~uni.ng that the noise
generated at the input does not exceed, on the average, five. times the
thermal noise, 3' 4 we obtain, far aHall-effect sensor having a source
resistance of one ohm, the open-circuit noise voltage generated in the
frequency range of 3 kc, at roam temperature,
YN= 4kTOf5= 4x 1.38x10-23x300x3x 103x5 = 1.6x10-8voit.
Thus, currents down to two microamperes can be detected over
the frequency band of 3 kc. If narrow band filters are provided at the
output of the amplifier, smaller currents, or the same currents with
improved signal-to-noise ratios can. be measured. In using awide-band
amplifier, in the manner indicated above, the currents. in the frequency
range of the amplifier can be read directly at the amplifier output, or dis -
played on an oscilloscope to represent its waveform.
The construction of the current meter in the form of a toroid
around the conductor reduces considerably the pickup from external
fields. It is of interest to note that the position of the current-carrying
conductor with respect to the center of the toroid is not important. This
3 Oliver, D. J. , "Current in Indium Antimonide", Proc. Phys. Soc. B. ,
London, Vol. 70, pp. 331-332; A[a.rch, 1957.
4Suits, G. H., Schmitz., W. D. and Terhune, R. W., "Excess Noise in
In Sb", J. App. Phys. , Yo1..27, p. 1385; November, 1956.
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follows from the fact that for materials with relative. permeability ~r ,
the field in the gap depends mainly on the length of the gap, and is almost
independent of either the length or the location of the high-permeability
magnetic -reluctance path.
Our proposal for item (c) encompasoea the designing, fabricating,
and testing adual-channel modulator playback system and modification
of an Ampex Modal 350 transport mechanism. Two estimates are given,
one fo.r (I), adual-channel modulator system and modification of the
transport for 1-?/8 and 3-3/4 IPS operation, and the second, for (LI),
development of L-shaped gap record anal modulator playback heads with
associated electronics and modification of the transport for operation at
1-7/8 and 3-3/4 inch per second. An alternative to the second estimate
is (IIA) development of adual-channel modulator system and modification
of the transport for operation at 0.06 inch per second..
The two estimates are given for your consideration because of
recent conversation with your representatives, indicating a desire for a
total speed reduction, from record to final playback on the order of 1000
to 1. If this is to be done in two steps., that is, recording at 60 IPS and
playback at 1-7/8 IPS and re-recording this reduced frequency signal at
60 IPS and again playing back at 1-7/8 IPS, effecting approximately a 1000
to 1 frequency reduction, the final recorded wavelengths of the low fre-
quencies become several inches.. The output of either a velocity or mod-
ulator type playback head approaches aero as the recorded wavelength
increases beyond the head-to-tape contact length. It is th?refore neces-
sary to either accomplish. the reduction in one step, thereby eliminating
re-recording causing expansion of the wavelengths, or by employing
L-shaped gap heads . An L-shaped gap head is a composite. of a
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.:*ry~ 1.t1..~ ~F.l! T. R
11!e K .~ia .
.?.. A~F'Y~ W.h~-
longitudinal-gap and transverse-gap. head. This type head allows record
and playback of signals down to and including zero frequency, which gives
infinite wavelengths without reducing the high frequency capabilities of
the system.
If extremely fine playback gaps (rnicrogaps) are employed to meet
the frequency response requirement of paragraph Z.9 in the specification,
a fairly poor signal -to-noise ratio will result. If conventional quarter-
mil gaps are used, an unequalized signal-to-noise ratio- of 50 db can be
obtained. Using equalization, the overall sigxaal-to-noise ratio will drop
to about 40 db and the system response will be flat within + 1.5 db from
0.03 cps to 3500 cps at 3-3/4 IPS with the signal level down 12 db at ?000
cps. Some experimental work will be done to improve the signal-to-noise
ratio and system response in an attempt to more closely meet your
requirements .
It is believed all other requirements called for in Specification No.
60-A-1114-A can be met. Time and cost estimates for the three proposed
systems are given on separate attached pages.
Brief monthly reports will be submitted describing progress,
results of work carried on during the previous month, and plans for the
next month's work. Upon completion of the program, operation and main-
tenance instruction manuals pertaining to the modifications made on the
Ampex transport mechanism and the modulator playback system will be
provided. Also, the modified Ampex Model 350 magnetic tape transport
unit will be delivered equipped. with adual-channel modulator playback
head and electronic auxiliaries. A spare dual-channel modulator head
assembly will also be delivered. In the event the alternate approach is
pursued, the modified transport will be delivered with special dual-channel
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~~J
~.
~'~v ~~~~~A~
L-shaped gap record and L-shaped gap modulator playback heads with
record and playback electronic auxiliaries.
It is hoped this proposal fulfills your requirements and meets
with your approval. SiVe look forward to being of service to you and your
staff .
CONFIDENTIAL
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(.11
ta~or Hall-ifteot Ma~etort~era plea 'itiro w~plitiera
Optiow I - The senaitl~rity of the Hall-effect Sensors should be of th*
order of on? aiarogauss. Y>br tregvse-+ct respocue of the senoor
shoald be crow abaut S op~ to 50 app.
TI1~ /JID COST I~STIMATR
It is estiwatod that 3 worths rd,ll be regairad for pertorsianoe of tbs
roaearoh effort.
Salariea~
Rn~inaer (1?? aon-wmtb at i~50/aro ?, r-~.) = 850
Teebt-iolan (1 ran-worth at BOO/~w. a~~.) 500
8bop aerrioe? labor (inel.ader Drattin~)
100 tiaurs at X3.60/h~oa~ 3~
9alars related ooeta: (irploTee is-saraaq ,
F.I.C.1~, ~aaatlona, acid slot lie) ?ati.rated
? at 204 ~_.._
Total direct salar~r oorrta
Oterhead at actual oast, eatiwated ut the approved
aarernarnt bi ddin` rate of 894
= 2,052
>s 1, 826
t+~raLaswd .acp.ndbl. wateriaL, auppli... and aertioea
; 500
Parciias+d pneral or apeoial egztipwnaat
:1,200
Lbns diatanoe aad tele~rapR
; 5D
Report reparoddotlon
~ 5Q
PaakiA g, aratind aad shipping ol~ardaa
= 100
Msd tee
,~lu~
Total Eatimatwd Cost S 6,It1~
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(~ 1
De~tioprnt at a Hall-Ettaot Magneto~rter
pptlon II -Utilising alternating e~u~reaets. The ruccess2til co~pletioa
of this progru should result in higher sensitivity of ^easur-
ing altensatl.ng aagnetio tields and the asaanteaent of steady
? ~ aagnstic rielda belo~r 5 ops.
TIl~ ~ 006T tiSTIlL
Sal,ariea r
engineering (3 a~no~-#oaths at ;850/ao. a~rge) ~
2,550
Techniciaa (3 asn?aonthe at =500/~0. a~g~)
1,500
Shop serTlcea labc-r ~incl~ndN, Dzatting)
3~ ho~-re at ~~e~~10nT
1,~0
Salary related coats: (Sapl,eTee ~renrance,
1~.I.C.1., ?acatioas, and sick lease) sstiaaLed
at 20Z
- ~
Total direct salary coats
? ~',.~
O~erheed at aatnal Dort, estiaated at tkn appr~o~ed
()orarnasat bidding rate of 89~
; 5,479
larchased ezpendable aaterials, sub?plies sid services
= 1,000
purchased geaeral or apeelal equipwsnt
~ 1,200
Loac-g distance telephone sad t~lsgraph
: 50
jleport repredu~otice~
_ ~
? leekiag, orating and shipping oharpe ~
; L00
l~ixrd tN
~--~-_~
Total Bstisated Cost W~,877
It is eati>r-ted that 6 aoaLl~s dll be requir*d for pezforsisnce of the
reeear~h etf ort .
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(H )
De^nl+sprat o! a "Clamp-fin" Hall-fi'tect ~teasor vi.th one At~plitier.
Sensitivity should approach 2 ~nicroaaQeres in a fregn~ncy range of
3 ~C .
'i'I~!$ AtID C06T FSTIMiT=
SalarLsst .
~i.neerinS (2 ara-iaati~s aL ~850I~o. ark.)
~ 1700
Tsolniei~aa (3 s~aa-nainth? at ;500/r. a~~?)
l,spp
Shop serrioe? labor (inolsdes drattiai)
300 atian hours at #3.60/ho'r
1080
Salary related oosts~
F~I,Cp~,, ?acations,
at Z0~
(iploTe? insurance,
and rick lesre) eatinatod
~ ~
g~
i 5,13G
Overlrad at aatnal coat, ?atiajated at the approved
Oovernraert blddin~ rate of 99~
~ b,S71
Purebas~d ?xpenda~Dle oaterialr, sv~pp~lies and eer~viaea
; 1,000
Ptirahased general or special eauip~siat
~ 600
Long distaaoa teLpboxra and teleOrapb
~ ~
Report nprodnotian
# 5p
Paclda~, oratiad and sbdppia~ ehar~es _
; 100
~'iztd toe
~ 6pp
Total Srtiaated Cott
x.2,19?
It is eatSaated that 6 ^antha gill De required for pertornaace of the
r~uroh effort.
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(C )
I Dral Cbrmol Msdalatos Plgbaalc lhjtt~s for 3 3/1- aad 1 7/d IP'B
?Ili ~D COB? l0?D!l!i
~~~ 1i ~.~.r~
~ P~'Krv of 6 a~ootat itiratian la pzopos.d :[or tlr dssigan, drrt.loprat,
eooatroation ana t.atin~ of a dual aluaaal a~odulator qat.^ aad ~oditi-
aatiaa of tba ta~po transport aralbarii.A tcc aDae~ation at 1 7/b sad 3 3/4
IlB. ?ha ~~i .Dort, and tha raaaltiaB aost .stLaatsr aonaidas.d . . _..._.
to Da aaaoaawr~- to adogtiato~ paetarn td ?urlc aa1Ld tos is ot~tlird as
toll~wr~ e
dalarioa~
iilaa.tLi (k aw~a at ~il50,~ar. ark.)
i3,liO0
taabni.oiaa (6 aaa-~ontlu a~ ~6O%r. a~~.)
Bboy (3OO ranra a ~3.6o/sort)
Dratti aB (80 t~onrs at ~ .6%our)
Salas~ r.Lt~.d aorta: (Lipl~ryro L~traot.,
l-.I.C.~., ~aaatiaaa, sad daft Lav~o) .stiartod
at Z0~
3,000
l,ur,o
2tl?
1.-~-
Total salari.a
S 9,322
o+ar~.aa at aateal coat, oati~at~.d at e9~
8,296
HaariaL aa-d 84pp1L.a
1,040
trav+sl
30O
Load Diataooo TaLphana and Tolap~aph
20
Aaport ltaproduotioa
50
l~i~wd ?w
1 1
i'atal Ssti~aatod Cost
=2O,1?2
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II
~I~
Deal Chaanel L-.;,ap Modulator Playt,acyc System for 3
or
Daal Channe'_ Modulator Playback Syetew for 0,06 IP3
3/4 +und 1 'l/~ IPS
TI1~ JIAiD C03r E3TIMA'i'E
~~
A 9 noath prop,~?aa 1+~ propoaed far the <emnati~re Rcope 1nvolvinK either
the L-shaped-gap heads or the, mods?lcatioa of the transport far O.C+6 IP3
operatioa~ The enginfering effort, and th,e result.in~ cost eatia-ate to be
neoessaty to adequately perforx the work called for is outlined as toll.owb;
~gineering (6 waa-~oatba at X850/ao. rn-g?)
i5,i00
Tec ion 1c tan (8 s~ -wonth a at =500/s-o . av g a)
1~ 000
Shop (500 hours at X3.60/hour)
1,800
Drafting (160 hours at =3.60/hour)
S76
Salary ~ related costs (Lglepree insuraace,
FBI ?G otu, ?acations, and sick lsars) estisiated
at 20~
2,295
Total 3aLaries
i~7.3,??1
OTerhead at actual cast, eetiaated at 89~
12,266
Materials a:rd 3uppliea
2,Q00
Trani
300
Long Di st anc. aad T.:1? graph
Report Reprodmction
zo
50
Maud Fee
....~
Total JBstiaated Cwt
=30,101
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