U N u L A b b F E D T̂ >i« Documtmt Consists of s / PURCS

This is Cot)y 7^ of 41A

MUI-561 Date.

Contract Number AT-33-I-GEN-53

i ' ^ ^ ̂ H'H'i

MOUND LABORATORY

operated By

lONSANTO CHEMICAL COMPANY ^

MIAMISBURG. OHIO «^

§^

REPORT ' ^ V FOR ''^

GENERAL RESEARCH

DECEMBER 26 , 1950 TO APRIL 16 , 1951

(SuppttrtlnR Research Volume)

This documoit is PUBLICLY RELEASABJLE

r to ted.

Date May 2t. insi Approved By:

Laboratory Dlrac

•'-UNCLASSIFIED

DISCLAIMER

This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency Thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof.

DISCLAIMER Portions of this document may be illegible in electronic image products. Images are produced from the best available original document.

UNCLASSIFIED 1̂ niMbLrtooiriLU «'5Gi nTSTRIBliTifON

I - Ciirroll A. r'nchnnlt

issued JUL 2 7 1951

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Burbaec Ilurine S t a n i f o r t h Anthony

McCarthy E i c h e l b e r e c r

Ileytl !i!ead , lr.

M i l l e r Payne, .Ir.

Jlcehan Renbolrt

S c o t t Panbl0

Olt Parks

PCROld Timnia

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Hood IHcEwcQ

Orban M.

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Prather Richmond

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Manaeer Manager

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Central P i l e s • Central P i l e s - Central PjleH

-2 UNCLASSIFIEQ

II ^,ipJ*>liig''4T—ty^y MLM -561

' AfiLE OP CONTENTS AND MAN POlffiR ANALYSIS

(Supporting Research Volvme^

SU,MMARY

Countinn System of Wide Dynamic Range, W. H. Baker

Fast-Neutron Survey Meter, J. F. Combs

Stable Energy Independent Gamma Monitor, A J. Rogers

Mechanical Integrator for Improving Counting Statistics A ,J Rogers

.Ab.sorption Studies on a Nuclear Instruments PC-1 (Bradley) Counter, M L Curtis Probletns in Beta Counting, M L Curtis

The Standard Torsion, EQual-Arra Balance. M I. Gray, R G Olt, and J H Wright

Mass Spectrograph, Don Haas

Total

Man Months

2-5

2-5

0.5

^•5

1.25

1,0

S'O

3-0

1J.25

Page

4

6

24

28

32

34

36

37

51

-3-

^jDr^f-TM-kT MLH 561

SUMMARY

Tilts volume present.s the quartorli resul ts ol that portion of the research and cUn-olupment «hiph u. directed towards estabU-^hing new teohniquos and instruments and towards improving present method.s for determining levels of radioact ivi t j accurately and sulel j

The lorallv developed amplifier of high gain and of wide dynamic range has l)een shewn to provide plateaus .suitable lor the simultaneous counting of alpha and beta pnrti cle.s Coramercmlly available amplifiers have failed to exhibit suitable plateaus when used under the same conditions This locally developed amplifier m conjunction with the Nuclear Instruments PC 1 churatjer has made it possible to estimate beta energies down to 0 02 million electron volt *hich is to be compared to u former lower limit of 0 1 million electron volt {p G)

A last neutron survey meter must be simple lightweight portable and efficient and mast provide discrimination against gamma raj-s The f i r s t step which is the design of n sui table detecting device has been successfully completed as good efficiency and good discrimination agamr.t gamma rays have been achieved The necessary electronic c i rcui ts must nm be engineered to provide the requisite simplicity l ight weight and portabil i ty (p 2'n

A stable energy independent; gamma monitor has been achieved through the use of a well regulated power supply and a highly degenerative amplifier The monitor maintains I ts accuracy withm t 2 per cent when calibrated once per day The direct coupled amplifier is capable of measuring currents of the order of 1 x 10"*'^ ampere (p 28)

A continuously operating a i r monitor for health protection must be capable of providing rapid response aid good counting precision when operating a t low-counting rates These requirements have been met by devising a switching device which permits the a c cumulation ot charge on a sequence of condensers for arbitrary time intervals. Discharge of the setjuenco of condensers operates an alarm if the rate of accumulation of charge has been excessive (p 32)

The Nuclear Instruments PC 1 chamber has been under investigation for use in the measurement of the energies of soft beta rays by absorption RaD and RaE mixtures have been used as "knovsns" The resul ts are in substantial agreement with the l i t e ra ture values Cp 34)

Several local problems m the use of the Nuclear Instruments PC 1 chamber are under investigation The beta rays associated with thij polonium alphas are being investi gated by studvmg the behavior of the Nuclear Instrumisnt PC 1 chamber when f i l led with argon or methane atid exposed to natural or a r t i f i c i a l polonium sulfur 35 or phosphorous 32 Polonium samples are being calorimetered to obtain an alpha plus beta determination and the samples are being counted to get an Independent alpha determination so that a comparison cdn be made to check for the presence of beta act ivi ty The effects of secondary electrons from absorbed radiation is also under investigation (p 36)

Routine operation of the quartz-fiber microbalance has been improved by the development of interchangeable panholders The quality of balance parts has been improved by providing bett:cr regulation of the pressure in the gas lines for the microtorches (P 37)

JaifSrft>B T-

4

.jfca:s=6-fr-eni^ MLM^SBI

The mass SIKTtrograpli is being modified so that it may operate e i ther as a six'ct rograph or spectrometer Operation as a spectrometer is som(>tiraes desirable since I.sotopic aljundanres can be determined more precisely with a spectrometer I t will soon be nuce.ssarv to measure the isotopic punt3 cf polonium 20B samples (p 51)

mm^S'^9SC'K:EZI,

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U N C L A S S I P I E O MLM-,561

I'l'H^lf't Tttle rmiii l it i i , .S.vsrems oj Hide ilyiramic Range

Rehn t '

U N C L A S S I F I E D MLM-.'iRl

loading, It seems possible to obtain the necessary increa.se in dynamic range required by the increased gain of the head amplifier Remote mounting of the head amplifier reduces ciipacitivc loading of the ionization chamber i thereby minimizing pulse integration and attenuation but it demands one common ground lietween the head amplifier and main ampli-fier. A common ground is accomplished through the use of double shielding, two-way receptacles and common grounds within the amplifiers The head amplifier case was con-structed with copper-plated steel for optimum electrostatic and magnetic shielding, and ttie outside of the case was chrome plated to minimize corrosion.

It has been found that the configuration of the input network of the head ampli-fier Is very Important, The load resistor of the ionization chamber has been set at 1,000 ohms becau.'ie of the sharp pulse developed across it (0 l-microsecond rise time or better 0 1-mlcrospcond duration at 0.60 inaximtm amplitude). The effect of the grid resistor and coupling condenser of the input stage should be optimized, so that the pulse at the output of the amplifier has a minimum duration without developing objectionable overshoot The value of this grid resistor will hove to be different with different overall amplifier gains. This is because the normally insignificant trailing decay voltage assumes sizable proportions when amplified 10.000 times in a limited amplifier.

Because of the extremely fast rise time of the pulse, it is possible further to Improve the dynamic range and the resolving time of the amplifier by sharply differenti-ating the pulse before it is applied to the trigger pair. This differentiation and the fast rise time of the pulse increase the sensitivity of the system from 80 microvolts to approximately 50 microvolts. Since spurious counts are not detectable with a maximum usable input pulse of approximately 0 5 volt amplitude it appears that this amplifier has a dynamic range of at least 10.000

The overall amplifier gain-bandwidth curve is shown in Figure 6 The bandwidth is 3 decibels down at 3 megacycles for an SO-deeibel amplifier whose sensitivity approxi-mates 80 microvolts. The main amplifier limits at 3.75 volta, while the maximum usable pulse from the head amplifier approximates 3 5 volts. The amplifier gain changes 2 5 per cent for a 1 per cent change in line voltage

Figure 7, A B. and C and Figure 8A show the pulse at the output of the head amplifier, stogos 1 2 and 3. respectively of the main amplifier, and Figure 8B shows the pulse at the output of the differentiating circuit. Figure 9. A and B show the noise output of the araplifler and the noise at the output of the differe»itlating circuit.

One of the best criterion of a counting system operation is a plateau curve of counts versus voltage. Figure 10 shows the plateau obtained with an alpha sample and a commercial amplifier. It is impossible to obtain an alpha plus be*a plateau with this system Figure 11 shows the alpha and alpha plus beta pleateau obtained with the described amplifier and a standard scaler

Up to the present time, routine beta absorption studies have been limited to energies of 0.1 million electron volt' because of the thickness of mica windows in Gelger-Muller tubes. With a windowless proportional chamber and a hieh-gain. wide-dynaraic-range amplifier it has lieen possible to measure weak Ra-D beta energies of 0.025 million electron volt. Figures 12 through 16 show the graphs used in determining this energy level with feather analyzers as described by Glendenin.' The measured energy by this method was 0.022 million electron volt A similar amplifier has been in use for 10 months and has proven very reliable

UNCLASSIPIED

http://increa.se

U N C L A S S I F I E D MLM 561

REPKHFNCES

1 Elmore and Sands Electronics .Mcliraw Hill, New York, p 159 (1^9)

2 Glendenin L Nucleonics 3. pp 17-27 (January 1918)

U N C L A S S I P I E D

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,=:=&J6s«S=1PirT MLM-561

'' '••,!ri T * ( l'a.«>it Nt'iitron Survt'.y Meter

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INTROnilCTIOS

The tievc lopiik-nf of n f as*-nt-iitron survey meter was undertaken to provide a huitjl>l(> iiistrumf-nt for thr deioction ot fast neutrons At the present time there is ri'i auch iiustruniunt avuilablf which i.s .simple liBhtweight, and portable

The dp.siCT ol the delprtine device was ol the greatest concern ini t ia l ly This dctertor consi.st.s of K chamber t i l led with methane gas which will operate as a recoil propor'iondl counter Gamnti discrimination is accomplished by liraitinR the physical size (it IJK- chatnbti Thu.s the electron path and the resultms pulse amplitude can be limited ' o fiiiv df;iii«'d valut The counter is fully described m a previous report "

The final model of .several counters built and tested resulted m a fast neutron lountuu; 'ffic.it'ncy ol 0 2.T per cent at a sensitivity of 5 millivolts when 2 350 volts v.f5» .ippl lod to ith center electrode Oarama radiation was not detected at the same sensi-t ivuv urn ll the cuuntct voltase was raised to 2 400 volts

At this point in the development ol the fast-neutron siTvey meter emphasis was si'itii-d liom th( det.ectHiR device to the necessary electronic circuits

IlETAILKII REPOIIT

Two ndcpt-ndem electronic circuits are required to operate the survey meter ."in ( ' Ik jfi-sf unii-nt i.s to he portable both circuits must be battery operated and both .iiiij si n. 1'itnp.if I .iiid !iph«wf-icht To provide a means of indicating the number of fast It. us 1 on.. (It It-red \i\ ) l.i proportional counter a rate meter circuit is necessary To pio >i:i> !hi 2 400 \ o i t s ni;ri>Hsa''y to operate the counter a high-voltage power supply is

A f.uc-tncTf'" circui t (Figure i) was built which employs a smele-staee pulse an;;.I 11( i wiih an approximate gam of 10 The output of the amplifier fires a thyratron tutu whi. ti hah Tti.- '.urialilc 500 ohm resihiance connected m parallel with the microammeter and i 000 ohm -ie» ii;.s usifetor allows tor calibration of the meter The circuit provides three icji '- oi sfm.it jvi'.v lor full scale deflection of the meter by varying the time constant 111 . „(• iij.'iti- Ci'fuit of the type RK* 61 t;hyratron When switched to Its most sensitive (am;'- iyi:>ilion C u fast neutron flux of 100 neutrons per squared centimeter per second P!C)fiu'_

rj^bfeteS- MLM- 561

Th«; hiRhvoltagi^ power supply reaulred to operate the counter must be regulated uiKi must pn)du(;e n voltage of appro.xiinat;ely 2,500 volts The use of eight or nine 'lOO-volt drv (•(>!! hattenes to supply this voltage results in a bulky and heavy instrument and the butteries are co.itlv to replace It was therefore decided to design a miniature piilsod-tvne, pow«-r .supplv Of the several types of circuits available the neon bulb-relaxation oscillator type ot pulsed power supply was chosen because of its reported high efficiency" and because it recpurcs the smallest number of components Several circuits were built and tested utilizing the relaxation oscillator and straight rectifier or voltage doubler cir-cuit.s The most satisfactory results were obtained with the circuit shown in Figure 2 The (iinkc used in t.hc plate circuit of the typo 5678 tube is a United Transformer tvpe 0-5 It IS very .small and weighs approximately one ounce. The wave shape of the induced high voltage n, th(- tvp 0-5 choke was such that the conventional type of voltage-doubling circuit did not operate satistactorily. The negative portion of the high voltage pulse was much smaller ' han the po.sitivr- part The circuit shown in Figure 2 makes use of only the positive portion '•; th(> pulse While this circuit does not double the voltage, it increa.ses the voltage out-put h\ ahnut 33 per cent over that achieved with a straight rectifier circuit. The high-volt HKO output IS regulated by a series of corona regulator tubes. The type 5841 tubes regu-Isiie ;it 900 voits each and the type QF--771 tube regulates at 700 volts giving a total regu-lated voltage ol 2 500 volts. Sub-miniature tubes are used throu(5hout the circuit an" iiU iHif the tvjx- 5678 tube are of the cold cathode t.ypo. The power supply operates at isi '-ull eitieiencv ol 10 j-er cent a ripple of approximately 10 millivolts appears at its n .and at ,5 inirrnamE)ercs 2 .500 volts is available from the regulated output.

Knowing the battery current drains required to operate both the rate-meter circuit apf! the high voltage power supply circuit the number of batteries required for 150 hour-̂ o! -service wa.s determined. The filament voltage for the t.vpe 5678 tubes and the type RK-61 tube will be .supplied bv Mallory t.ype RM-12 mercury cells The 135-volt plate supply for iHtth the n-iaxa,'ion oscillator t;ube and the amplifier tube will be supplied by the same burterieH The fi 5-volt plate supply for the ttiyratron will be supplied by a separate h,tM"r\ This voltage must remain nearly constant over any one calibration period if the '•aiibratinn i.s to remain accurate The 4 5-volt negative bias for the thyratron tube will he sunpljed by three Mallory Type 1 RX mercury cells connected in series.

TlK design of a prototype instrument was Initiated. Several parts were under con siriictioii when work on this problem was temporarily discontinued

UflFEUENCKS

! Combs .1 P Quart Rpt Gen. Res MU1-529, P 12 Jan 29 1951

2 ilurst G S Portable Past Neutron Survey Meter ORNL - 485.

3 Thomas (i. EloctroniCK pp 100-103 Dec. 1948

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' ' '• ^ '*'•' stable,Ener(» Indepcnilent Gamma Monitor

• ' e ' ' /i \ .1 Roger:*

•ui'i iOru' I'n A ,1 Rogers

INTRODUCTION

The development of a gamma monitor which is energy independent over wide ranges Aas reriuired for health protection purposes m areas having a high gamma flux The monitor ».is to be operated on alternating current ent irely It was to be capable of quantitatively indicating the gamma-radiation intensity in the ranges of 100 mllllroentgeas per hour and .•̂ 00 milliroentgens per hour full scale Means for the remote operation of the detecting 'hviro were to be provided An instrument incorporating these features was designed and a rode I IS being constructed

Df'TAILFn RKPORT

The completed gamma monitor includes the following ma.]or components a high 'iressure ionization chamber a dirccc-coupled amplifier and associated metering c i rcui t .I'v! mTpss.ir^ regulated and stabil ized power supplies

The cylindrical high pressure ionization chamber has a volume of 800 cubic ci nrimetors It is f i l led with argon to a gauge pressure of 150 pounds per square inch rheorv indicate? that this chamber will reach ionization current saturation when the

lertrode potential difference is about 200 volts I t is at this potential that electron oUef r io i i (jTjurs before ion recombination effects can dimmish the ionization current '•xper mental evidence validates the theory

'Aith the correct electrode polarity the flow of ions under action of the eloctro-stdtH field existing between electrodes produces an electron current a t the center elertr'idfj of the ionization hamber This current flows into an integrating network and is i . t i l i / ' d to change the bias of the input stage of the direct coupled amplifier (See Figure 1) ''liii ir 'siiJier i.s essentially a unity voltage gam or current amplifier The electron cur--eni j,r riuceri m the chamber for a gamirci flux of 100 millircentgeas per hour is about I . \ 10 o Biiipt̂ res With an input resistor of 4 x 10° ohms this gamma flux results m a po tt ti.ii change of approximately 0 5 volt at the input to the amplifier Since the amplifier hi-. I' n desif;ncd for unity voltage gain the equivalent amplifier outout is also 0 5 volt The tinti'If i

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The rilurient potential tor the switch is supplied bv a Miillory t.vpe RM 4 mercury e l l This rotentiul ih applied by closing a switch on the power supply chassis Calibration of the irii.tnitnent miiv then lie performed at the power-.siipply chassis also The direct coupled ampli-fier All! maintain i t s calibration to within ^ 2 per cent over a 24 hour period

T'Ao .separate poAer supplies are uti l ized to provide ull necessary eloctr(XlP potentials One power supply is ca.scaded upon the other The more negative power supply provides a siabli- ionizing potential for the itinlzatton chamber The more positiv" power -supply providt-'s all electrode and filament voltages for the amplifier and metering circui t These pTOor supplies are identical in design (Figure 2) and were suggested by an a r t ic le bv Peter Siilzer appearing in the December 1950 issue of "Electronics." enti t led "Stable Kiecinmir Power Sutipl.v " The power supplies are conventional vacuum tube direct current .'ippltfier regulated power supplies with increased s t ab i l i ty provided for through use of .1 heater voltage compensating network

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Problem T%tLc Mechanical Integrator for Improving Counting Statistics

Report By A. j Rogers

h'ork Ihne By A J. Rogers

INTRODUCTION

There is a need in health physics applications for a monitoring device that will combine rapid response with good counting reliability at the low counting rates normally found in health ph.vsics counting.

A mechanical Integrating device which fulfills these requirements was developed for use with a continuous air monitor for health protection where minimum time lag be-tween the occurrence and the detection of changes in the contamination level was required, together with good statistical counting accuracy.

DETAILEn REPORT

Since the response of the mechanical integrator is to be dependent on the input pulse rate, it is necessary to convert the input pulses, which are random in time, into voltage pulses that are uniform in shape, amplitude and duration. This Is accomplished by a pulso-shapmg network which precedes the integrator.

The charging network of the mechanical Integrator utilizes these uniform voltage pulses to produce in a capacitor a stored charge that is proportional to the input pulse rate over a definite time interval. This capacitor is then removed from the charging net-work and a second capacitor inserted. The charge applied to this second capacitor is de-pendent on the input pulse rate also, and is evaluated over the same definite time interval. This procedure • continued until N capacitors in turn hive buen charged to energy levels which are in each case proportional to the input pulse rate. Cascading these N capacitors in series provides a total charge that is proportional to the total number of pulses ob-served by the detecting device over a time interval of NT seconds.T in this case refers to the time interval over which each of the N capacitors has been affiliated with the charging network It is this total charge that is available for actuation of an alarm circuit. After a short time delay to permit the alarm circuit to evaluate the total stored charge, the first capacitor is discharged and returned to the charging network. In turn the N capacitors are discharged and recharged with the alarm circuit, evaluating the total stored charge at all times This last feature permits the continuous sampling of a total charge that is equivalent to the preceding (N-l ̂ K) timing intervals, where 0 < K < 1 .

A three capacitor mechanical integrator is shown schematically in Figure 1. A series of motor-driven cams mechanically operate switches that provide for the proper sequencing of capacitor charge and discharge cycles. The input to the alarm circuit is permanently connected across the seriesed capacitors to insure continuous sampling of the input pulse rate.

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1 2 3 4 ALUMINUM ABSORBER THICKNESS IN mglcm^

ABSORPTION STUDY OF RADIUM D

U N C L A S_S I F I E D

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'• ' > ". 7 f.'i Prtiblems in Reta Counting

''",' M I, Curtis

INTUOIUICTIO.N

Two ol the problems involved in counting beta radiation in the type of samples submitted tor measurement at Mound are

1 To distinguish beta radiation from secondary radiation conimg from photons

2 To count samples very low m specific activity with a high and variable cosmic-ray background.

Some prt'lnnmary work has been done on these problems

DETAILED REPORT

Since mnthaiie gas is less efficient for counting gamma or X rays than argon Kub m(;asurements have been made m a Nuclear Instrument (Bradley) PC-1 counter with eu( h ol these gases First indications are that there is less "beta" in polonium with methane gas but results are not yet conclusive. Samples of pure polonium natural |)til >h urn impure polonium sulfur-35 and phosphorus 32 mounted on both glass and i.iat inum have been preimred and will be measured periodically over a period of time V. ith both Ka.ses This will indicate whether any of tbe apparent beta is caused by any Jurion of the sample material on the sample mount

Samples of polonium have been measured on the LogacS Five of these samples '.ill be measured simultaneously in the calorimeter Since the calorimeter will measure Sieta radiation and the Logac S will not this should give a further indication oi ami l«"u impuiitv in polonium

The piohlem of counting low-level sampler with a high background requires ;.,s. iii'-diis ul reducing the background for its solution A Bradley counter wits set up

m Room 37 of the "T" Building and it was found to have a beta background of 30 counts [jei minute compared to an average of approximately 60 counts per minute cosmic-ray bat.k I" ujiirl HI the R Baiding

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L' N' C L A S S I F •[ E D MlJil 501

The Standard Torsion Fxjual-Am lUilance

M 1 Gr.iy U C (lit and .1 II Hnght

V 1 Cray C L LPKIIIM I. A Jewett R « Olt Ji W Staiit.^enb4ch and .1 II nricht

I^TRODLI^TI()N

The quart?;-fiber microbalance in the form used in microassays consists of d fompietety fused quartz-liber beam .s.ystein of a torsion-fiber equal-arm load-balancing 1 M>e m a case containing the d i iec t ly associated mechanical and optical systems This unit 1.1 further enclosed in a vacuum tight metal housing f i t ted with the mechanical and npt i ia l controls and accf.ssones essential for placement weighing and removal ol .sample bearing foils while maintaining atmospheric thermal and radiation shielding Since the Ciirrieih loi the foils also provide atmospheric and radiation shielding it is possible to operate the balance m low risk areas despite the high level of ac t iv i ty being handled

Because ot the high level ol internal contamination repairs to any portion ot 'he quart/; Iiber microbalance or housing requiring the opening or exposure of the hnu.-;nig inter 10! must be performed in a high risk area with a l l health precautions suggesred tor hish risk wnik Since the balance is used in a low-risk area i t is also necessary to toll'ift a l l interaroa contamination control procedures As a result internal balance service 1.S a lengthy procedure which often requires delicate work under diff icul t con fhisons

Incorporation of the mechanical e lect r ica l and optical refinements described ii! iireviou.:. reports - -' improved the operating characterist ics and extended the periods «i haian(e av,ii jabi l i ty to about a month at which time cleaning ol the pan well area would b< recjiiirfd Dessication of the balance interior further reduced the need for cleaning 'il tin pan viell ut'̂ a.s resulting in further extension ot the peiiodi. ol trouble free balance 'iiK-iiK I'jn tf) porr than six months •*

^ UMior factor m the increase of balance avai labi l i ty has been the development lit Miten haiiKeable panholders which eliminate the need for lemoval of a balance tu a high ri^k (Ue.i for panholder replacement and .subsequent loadjustment of pan arrests The im III »\ertient.s m panholaer mass dis tr ibut ion and size control have contributed also tn the .p.'.'d and ci ' i 'ajnty of the remote loading and weighing ol fiti Is

ttorkmg of quartz fibers has been adversely affected by microtorch flame changes tnd i !ashba( lis resulting from oxygen ariu fuel gas supply pressure variation Measurement fi( gas Urn pre£,sure.s for a 2 4 to 1 range ot flow rates showed pressures varying from il in hf's to 9 inches of water m the oxygen line and from 21 inches to 12 inches ol watet Ui the prop.me line when using two stage cylinder gas regulators

Better control of pressure has been obtained by addition of the third stage (..omponent ot the Airco Style 1608 three stage nitrogen regulator for oi l f i l led trans t'lrmers Thus component which has not been sold previously as a separate unit shows a pressuip regulation within 0 6 inch water at 14 inches over a flew rate range of 0 32 ci ) 40 cubic feet per hour

U N C L A S S I F I E D

37

U N C L A S S I F I E D MLM 561

DETAILED REPORT

tjiiartz Filler Puntiiildors

Early at tempts to make usable quart?,~fiber panholders according to Argonne dimen.sions and procedures'* proved uniformly unsuccessful bocau.se of incompatible poise and ilimensnin a(l.|ustments A p a r t i a l explana t ion tor the lack of success might be that whii. the Argonm typi m;tiimuin t i l l on arrest rcjleaso is shown m Figure 3

Fipine 4 shows panholder j ig A which is used for fusing the cross leg to the ptjneifji] memlKi and for making the two bends that position the ring The remaining bend inj; np< rat loas are peiloimed on panholder j ig B Figure 5

The curren' method of constructing and inspecting fused quart/, fiber panholders is il! tol Idws

Cons true:(ion

An 8 < ent imiiter iciigt h o! 175 micron fiber is cleaned with chrnmit avid w,iter .•n(! melon' beion- appUoalnin ot tht working flame. With thf fiber held m n near vet! ua l position a sharp 45 bend is made about 2 millimeters from Ih'̂ ne

U N C L A S S I F I E D MiJi) sm

The inspected t u c k and storo is rcixxsit loiied and clamped in jig A .so rhat the c i rc le IS centered on the engraved cro.ss lines (Piguie 7A. A 6 centimeter ieiigih of 175 micron f ihei is clamped in the groove which is at 90 to the axis ol the stem and !1 millimeters from the center of the c i c l e

Alter tieaiung the fiber inteisection with chromic a n d d is t i l j ed water and acetone the 90 joint is fused with ».he usual precautions for avoiding distort ions and necking m the heated area

The circle is undamped and the j ig is rotated so that the c i rc le fa l ls away trom th'> surface ot the j lg wh3n the stem is heated J millimeter from t,he junction to the cross leg The bending and i ig rotation are continued until the c i rc i t iie^. on the a iu ' s t pm (Figure 7B) with the j ig horizontal The j ig is rotated 90 and the ntem is heated about I raillimetei trom the c i rc le to make the reverse bend bringing the plane of the (.irtle parallel to and 4 millimeters above the plane of the cross legs and stem iPigtni 7C; At this stage the center ol the c i rc le should be directly ovei the .-.tew and 2 5 raillimt'ters back of the .uncnon ot the stem and cross legs

The bent stem ring and cross leg assembly is transferred to | ig B (Figure 5̂ and the tro.ss leg fiber clamped in the groove next to the cut-out quadrant iPigurc- 7D for thi forming of the rear loot column and hook The f i r s t bend 90 downwaid is made opposite the index groove m the j ig (Figure 7E; with the ]ig m the horizontal position The tixtiire is then rotated 180 while lurming the U-shapod I miiiimetar bv 1 millimeter lear leg (Figure 7P) The column fiber should then be about i miUinfter tiora the bend of the circle support fiber The column is bent toward the c i rc le at the index G millimri»»r.s above tht fixture surface until i t fa l ls in line wirh the hook index 10 millimeters abov

V .N C I. A d S f F i: F. D MLM 5S\

Sl igh th un.sati,st.irt;',tefft which was supplied with oxygen and piopam^ from cylinders through Airco Style 8401 'M','Bun and 8462 propane two-stage regulators maintained adequately steady iim: pressures at the torch controls while the regulators were relatively new

U N C L A S S I P I E p

-40

'• '̂ control noticed a f t e r atioul nine irontlis local s.v'-tem operiitioti led to u siirvej oi the ."^.stem aiis pressiire.s and flow r a t e s vtsmometers »ere Ins^talled m both the iwtien î nd propiine !in(-s a t the r egu la to r headers and each of tfse quar tz working bersrhej. Since the Ix-rich tapM were 22 and 42 feet fror the r e g u l a t o r s on l /4 - inch copper ttitx- l i n e s d i f l r e n t i a l pressure Bsinometers were ins t a l l ed I't these poin ts to measure prrMs,ure drop m t f I iix-s from the headers Manometeri iiidi e a t i n g pre.s.,ure in the tsixin^t chuirtiet.-, of the torch con t ro l s were u.sed to otit.un du).l f a t ior< ot flame hlzi'h and guh tiow.s r lurirg trie Mir\ey

Flo* r a t e s of a nutaier of to rches nnd pilot .s were determined for large and sneill flame sf t t ing.s by water di.splucefrent time fien.su-o", rits Plow r a t e values for mixed ga.s ranged f ros 0 015 cubic feet pi-r hour far a 0 2 mil* meter o r i f i c e t i p at 0 fl inch raixmn chamber jiressiire to 0 77 r i ib i r feet pi-r hour for a 0 6 mi l l imeter n r i f i r e t i p at 4 0 inch mtting-chamber prrast ire The probable ex t rew.s of l]n» r a t e s l i k e l y to be encountered in the ?».\stem were es t i re i t fd from the cond i t ions of (A) one bench opera t ing with small torches ami flaw'.s and (B) t-*o benches opt r a t i n g with larg-i torches and tlames Taking the pro por t ion of one volume of propan*^- t o f ive volumes a^ the normal r a t i o of gases consumed e-,nii5ited flows range from 0 02 to 0 40 cubic feet per hour for propane and from 0 I tfi 2 0 cubic feet per hour tor oxygen

T jp i ra l pressures î nd flows encountered in the headers behind two s tage regu l a t o r s on changing from two bench f>{>eration to s ing l e bench operat ion were u.s follows

HEADER PRESSURE

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U N C L A S S I F t E n MLM 561

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Measiiroim'nt of line losse.s at the (wiximum rate of flow showed an oxygen [iressure drop tiPtween the header and f i r s t bench at the 1 4 cubic-leet pnr hour flow ot D (> inch of water Additional drop between the fir ' i t nrid .second bench At 0 60 cubic foot per hO'ir »as 0 35 inch water for a total drop from the header of 0 95 inch of water The propans* line pressure drop at 0 28-ct)bic-foot per hour Tim rate vm 0 15 inch water tietween the header and the second station Change of the oxygen line from 1/4 Inch tn 1/2 mch outside diameter copper tube lf» expected to reduce the lino drop to a value comparable to that for the propane 1ine

The decrease in header pres.sure change resulting from aririltion of the third stage of regulation has greatly ri^luced the d l t f i cu l t i e s experienced in attempting to control microtorches fc.- quartz l iber work Installat ion of arlequate flow capacity liii'ss should result in the elimination of detectable Interferences with microtorch flame control

RKPKHENCKS

1 Olt R 0 Quart Rpt Gen Res MLM 405 5 /,>p 9 21 Jan 1 1950

2 Olt R CI Quart Rpt (3en Res .MLM 443 5 pp 170 177 April 1 1950

3 Olt R G Quart Rpt Gen Rr;s MtJW 529 r>1i 23 26 Jan 29 1951

4 0 Donnell T J "Drawing and Working Quartz Fibers " A 3953 pp 27 29 March 1946

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U N C L A S S I F I E D

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U N C L A S S I F I E D

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FINAL ALIGNMENT

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PLACEMENT FOR HOOK BENDS D

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SECOND REAR FOOT BEND F

PANHOLDER CONSTRUCTION OPERATIONS.

U N C L A S S I F I E D

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PANHOLDER JIG B

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INDEX

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PANHOLDER JIG B

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U N C L A S S I F I E D

.50-

eritiientui and routine qualttutiV"' luial.v.sis and the investigation of radioactive and nonrudiouct ive isotopes

This iiloreineiitioned mass spectrograph Is now underKoinu u tonversion which will result in a muss spectrometer Retention of the Mattauch arrangement will permit, the sub •St 1 tut ion of an iun collector a.ssenibly lor the ptiotOBruphic pjute The ion source will be of the surface ionization type This spertiometer will be used lo determine the relniive ubundance of the a r t i t i c i u l l y produced poiterniination of ttie r e l a t i v e ubuuriiince of the 20B and 209 isotopes ol polonium produced in the cyclo t ron ut Oali Ridije

l)ef«'cl.iaii

[tecause the dens i ty of u l ine produced on a photntsiaphit p l a t e by an ion iKiom û no! r l i recf ly propor t ional to the miiBnlttide of the ton current producing the l ine the photographH nietiiod of d e l e d ion i s !o be di.scarded foi thin experiment In l ieu of the photouniphif plttt(« a probe t o weasure ton c u r r e n t s i s t.o be u.sed in a spec ia l Iv ron fitriicterl set of pole p ieces

A temporary probe has been const ructed and insorteri in the present s e t ol pole p ieces 111 un effor t to deteritilne the followlnn charac te r 1s t i c s

1 The proper design of the sh i e ld ing necessary to measure tht; ion cur ren t with a miiiimutn amount of background cu ' re i i t

2 An exi t s i l t l o r tfie cu r r en t probe

3 The magnitude of the ion cu r r en t neces'jary to d e t e c t i so topes d i f f e r i ng in mass tiy one mass uni t when present m a l to 1 000 ra LI o

4 A c a l i b r a t e d .s.ystem for varying the itBiKnetic f i e ld in terms of the i so top ic mass under de t ec t ion

A prel iminary experiment has been performed with burium oxide as a source niatoriul There a re seven isotopes of barium ranging in percentage from 0 1 per cent to 72 per cent

51

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in the samnle A to ta l ion cur ren t ol 5 ,v 10 " ' ' amperes was measured u t the en t rance to the magnetic f i e l d This r ep re sen t s t o t a l ions from the sample The l e a s t de t ec t ab l e i so top ic l i n e barium-134 which i s present in 2 4 per cent abundance was detec ted ut the ion c o l l e c t o r with an ion current of 1 x 10 ^•' amperes

In view ol these r e s u l t s the ion c o l l e c t o r assembly .shown dtagnimnuitically m Figure 1 has been designed Tlie s l i t assembly i s placed d i r e c t l y on the ax i s of the former photoitraphlc p l a t e D i rec t ly behind the s l i t a s t a m l e s s s t e e l Paruduy cup has been located A brass housing i s employed here so tha t the con t inu i ty of tbe a i r gap may he preserved Appropriately located a p e r t u r e s •lerrait the e n t i r e i o n - c o l l e c t o r assembly to be operated a t anal.vzer tube pressure The Pan day cup i s i onnoctod j o i n t l y to the e l e c t r o meter tutie and the gr id leak (a r e s i s t o r ol app-oximately 1 x 10** ohms) The Farudai' cup should suppress seconriurv e l ec t rons qu i t e e f t i c i e n t l y The e lec t rometer tube and grid leak are e lec t ros ta t ica l ly and electroinauneticaJ ly shielded tiy the steel housing the leads to the km potential ends ol the electrometer tube and grid leak are brought out of the vacuum chamber through Stupakoff seals The entire ion collector assembly can be removed from the pole pieces to fac i l i t a te ttie msta lhi t ion ol new coilectot slit*?

Source

The Shuw source previously employed is an integral replaceable unit that main lams no direct i ontact with the slit sections of the anaLvxing tube To recharge the source it IS necessary to remove the entire mechanism and the tollowing complications result

(a") Impossibility of realigning the source without an in i t i a l production ol ions

(b; The loss of sample material required lor th is ini t ia l pro duct ion of ions

Therefore It would appear ttiat a source which could be lecfiarged without disturbing the t tu t ia l uligrimeni would be conducive to investigiH lori.s with smaller samples The ahiiit> to use smaller samples liî conies a requirement when radioactive con t ami nut ion is to he inn imt'/ed

A source which would fuWill this quul it icution has been desipiied and is now m lonstruction Tfie source emplo.vs the techniqiios ol surface ionization for the prudurtion of ions It consists essentially of a filuinent anode con.structed ot tunitsten ribbon 0 030 inch wide and 0 001 inch thick This filament has a mechanism which will tieririt i t s re moval and replacem^-nt without disturbine the in i t ia l iilignraent This filament is aiao attached to the end of a brass sleeve which s l ides over the s l i t system of the specttotiieter Therefore once the source has been aliKtied with a nonradioactive sample a very small radioactive sample can then be run without the wasteful consumption of sample material

It IS well known that the surlace ionization techniques tan be applied to the alkali metals the alkaline earths and to the rare earths However the application of surface ionization techniques to the analysis of polonium (208 209) has never been investigated This investigation has been carried out in the followine manner

A filamiint constructed of tungsten ribbon 0 030 mch wide and 0 001 inch thick was coated with a 10-larabda sample of polonium {in n i t r i c acid) This filanient together

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with two stainless steel foils was then placed m a vacuum envelope The .stainless steel foils have been called foil A and foil B ^ potential ol 2 000 volts was then applied between the filament and loil A with the filament positive with respect to the foil The second foil B was operated at the same potential as the filanxint The ion current between the filament and foil A was measured and the following results were obtained

(a) An ion current of approximately 15 secwiJs duration was obsert-ed tor a filament temperature of 2 000*̂ 0

(b) An ion current of approximately 30 seconds duration was observed for a filament temperature of 2 200̂ 0̂

(c) A continuous ion current of 11 ramutes duration was observed for a filament temperature of 2 350''C

(ti) Above a filuinont temrierature of 2 800 C the ion current could not be observed

Upon the conclusion of this experiment foils A and B were counted with the following results

1 Foil A 8 53 X 10" counts/minute

2 Roil B 7 04 X 10" counts/minute

Poll A indicates the amount of polonium deposited liy the ion?zed current of materuil in addition tu the amount ol material deposited by the prtxress of distillation. Poll H indicates the nmoiinl of polonium depaslted by distillation The difference between the counting rates of foils ̂ and B (1 49 x lO" counts'minute) is an indlcction of the amount of polonium deposited exclusively b.v the ionization of polonium Therefore it tentatively appears nosslble that polonium can be effectivelj Ionized with surface ionization techniques

The conversion of the spectrogrnph to a spectrometer will result m an instrument thai can tiieusure accurately the isotopic relative iibundnnc'.' of any material that can be loni/ed with the techniques of surface ionization By the 'simple and convenient proce.ss of insert iiiK the photographic plate packing fractions can lie determined and qualitative anal.vsis perlormetl on all samples that respond to surface ionization techniques

RP'FKRFNCF.S

1 .Mattauch J Phys Rev 50 (117 (1936), AkacI »'iss Wien 145 4C1 (1936)

2 Shaw A K An Intense I'ositive Ion Source foi Solids Rpt No CP 3.159 1946

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