Gamma-Ray Wavelength Measurements of Gold 198, Iodine 131, Cobalt 60, and Tantalum 182 Using a Curved Crystal Focusing Spectrometer Citation Brown, James Roy (1951) Gamma-Ray Wavelength Measurements of Gold 198, Iodine 131, Cobalt 60, and Tantalum 182 Using a Curved Crystal Focusing Spectrometer. Dissertation (Ph.D.), California Institute of Technology. https://resolver.caltech.edu/CaltechTHESIS:08152025-205227845 Abstract A description of the two-meter curved crystal focusing spectrometer, including improvements in several of the component parts, is given. The systematic errors inherent in the measurements and the calibration necessary to determine them are discussed. The construction of a sensitive geiger counter for the detecting system was necessary and was achieved only after many failures. The over-all instrument sensitivity is low, requiring sources of the order of twenty to fifty millicuries. The gamma-ray spectra of four sources, Gold 198, Iodine 131, Cobalt 60, and Tantalum 182, were studied. In the case of Iodine and Tantalum the entire spectrum was not obtained because of the lack of sufficient source strength. The results for all these sources and the method by which they were obtained are given. Item Type: Thesis (Dissertation (Ph.D.)) Subject Keywords: (Physics and Mathematics) Degree Grantor: California Institute of Technology Division: Physics, Mathematics and Astronomy Major Option: Physics Minor Option: Mathematics Thesis Availability: Public (worldwide access) Research Advisor(s): DuMond, Jesse William Monroe Thesis Committee: Unknown, Unknown Defense Date: 1 January 1951 Record Number: CaltechTHESIS:08152025-205227845 Persistent URL: https://resolver.caltech.edu/CaltechTHESIS:08152025-205227845 Default Usage Policy: No commercial reproduction, distribution, display or performance rights in this work are provided. ID Code: 17630 Collection: CaltechTHESIS Deposited By: Benjamin Perez Deposited On: 18 Aug 2025 20:57 Last Modified: 18 Aug 2025 20:57 Thesis Files PDF - Final Version See Usage Policy. 32MB Repository Staff Only: item control page

GAMMA-RA. 'l WAVI~L£Nr}TH MEASU E~Gr1L~NTS 01', GOLD 198• IODINE 131• COBf.i.LT 60, AND TANTALUlvl 182 USING A CURVED CRYSTAL :FOCUSING SPEC'rR OMBTER Thesis by James Roy Brown In Partial l:ilulfillment of the Requirements For the Degree of Doctor of Philosophy California Institute of Technology Pasadana., California 19.51 'r he encouragement and many helpful sugges t;ions gl·ven by Dr. J.1.' . r.t • .DuMond are gratefully acl-s:nowledged . ri'he assistance of Dr. D.A. Lind in many phas0s of this work was extremely helpful. Th0 construction and assembly of the mecrianical part of the s pectrometer wore carried by or. J. w.M. DuMond before 191~2, with the help of Dr. W.H.K. Panofsky, Mr. R. Yost, and Mr. B. E. Merlwl, ins tru.ment maker. 'l"he assl8tance of Mr. D.E. Muller a..'ld tvir. D.J. Klein in many operations and discussions is gratefully a.ppl"dCia ted. The financial support of tho Office of Naval Resear•ch r;1 ade possible the construction of equipment and procurement of sourc es ·. vhich would not have been otherwise possible. ABSTRACT A description of the two-meter curved crystal focusing spectrometer, includ:lng improvements in several of ti.1e com;:, onent parts, is given. The systematic errox•B inhe :~ent in the measurements and the calibration necessary to determine them are discussed. The construction of a sensitive geiger counter for the detecting system was necessa.:v,y- and was achieved only after many failures. 'rhe . over-all instrument sensitivity is low, requiring sources of t i-10 order of twenty to fifty millicuries. The garnma- r ay spectra of four sources, Gold 198, Iodine 131, Cobalt 60 » a nd 'rant alum 182, we1~e studied. In the case of Iodine and Tantalum the entire spectrum was not obtained because of the laclt of sufficient source strength. The results for all these sources and the method by which they were cbtalned arc given. 1 B. Collimator c. CrJstal and aolder 9 ' D. Gei 1.; e r Counter and Cosmic- Hay ;ShlolJ.1ng 111. .Lr. .l·· Compm"ator Galibr•ation of iiaVelen.r;;-th .Jcrow 17 IV Absolute Galib r~ution of ,;avel eH1J;th Scrow 20 ~ 22 VI Automatic Obse1•ver 23 VII ,Je lg0r> Counter •Deaign 25 29 VIII ApplL:.:ation of Spectr·oi:2otor to hieasuromont of v ain.ma-Ray- #avolen6ti'"l.S A. Gamra.a-Hays Following ~ -Dooay of Iodine lJl 30 (Il_jl) . ~. 1.1 ar1-~i 1. 3 nic::y crwr1tna.-..i~a~{ Lin?~ Followi ng ~- ,)t1 c&y of Jobal t oO • IhG t1s1.1i-)<~rn~:>r1ts. of t.t'.10 (Go 00 ) c. D. 30 32 "' Uk~asu:rmnent of tine :+11 k("te_ '•uv Qgi)mna- :,ay f'ollo ,0 ing~ (3 ... Decay of i}old 19d ~ 1 "I 36 Check of 3pectrom~ter Screw Fnctor ( Tungsten K~l Line} 38 1. Hou gh D0t e r'lnina tion of 113 l{eV Line !+4 2. :1evision of Cor>k 1 s Dec.a,; :3c ::1·.'.m ie on Basis of · fires -ant Meaaur>ements 1~5 References 48 Page Number . of elect1.. ons in aluminum ~md copper 1. Hange .... ? Results of Gold 19d measurements 3. Rn cults of Iodine 131 nea.sul'erncnts 51 52 4. Hesults of Cobalt 60 measurements 53 5. Hesu l ts on high E3nerg:y lines of Tantalum 182 54 I Rooults on low energy lines of Tantalum 182 55 Tantalum 182 results .56 o. ~, I • sur:imary of 5. Compari.son of r•eported energ ies for Tantalum 182 50 .·57 2 .. • rrwo .M:e ·thods of Using Spectrometo:c' ). Geometry of Diffraction ll• Ab€n")ration D't.10 to Failure of Crystal to be on Pocal • Circle G. Source .dolder 7. Ends of Collimator 7A. Collimator ~indow Curve d. Crystal Holder ~. Crystal Slab 10. Crystal F'ocus Di a 15rrun 12. Anti-Coincidence Counters 13. ~ench Circuit 13A. Anti-Coincidence '.~u.ench Circuit 1 1+• Anti-Coincidence Circuit 1:;;. Tung sten Kl Line Profile l o. Gold 1')8 Line I1 rofile 17. Rang e of Electrons in Aluminura and Copper ld. Op timum Plate Tl1lckWJ8S F). Df:Jcay Schemes of' Iodine 131 20. Cobalt 60 Line Profiles 21. Cobalt bO Line Profiles 2c::. Cobalt 60 Line Profile 23. 'l'antulum 1H2 :JDectrurn 21.~. Tantalum survey Hun 2s. Decay Scheme of Tantalum 182 ,.::6 . .,f ofified Decay scheme of Ta ntalum l d 2 - 1 - Tt1e spec trom0ter us.ea in thL3 study of garm11a-ray ·,v ave 1 en .t h s nas o e en \ es c r t"bet1- 111-o'ttr?.:;t'7Tl.-rrc-e·s--<-L)_bttt-i-t is f01t tha t a 11~1o r t descri p tion is necessary here for com- pleten 0ss . This is a trans mission-type spectrometer which makos uso of' Bragg reflection'l:• from the ( 310) atomic planes in a quartz crystal. This qua.1.. tz crystal which is 2 milli- n::otors t l1ick ls curved to a 2 meter radius by clamp ine; 1 t against t r1e convex surface of a. stainless steel block ,vi:iic i1 1--: i.a5 bcon accurat0l;y- p rofiled to a cylindrical ;__;urface of this radiu s. Th.Ls crystal and holder wi;l.l be described in r:1ore detail later. If a giv,:m spectromoter sott;ing corres- ) Onjs to the Braf;t~ angle for a wav0len16th of 6 .-;.mma-re.y emitted by the s ource t l1en these garnrna-rays vdll be di f fracted by t i10 cr:,rstal and the d0tectini; system will re::.;pond. Of courue o nly a s t:;all f'ri1c 'c lon of the 1:;arnrna.-ra1s wl t11 this ;;1£w0length wi11 be d.if'frac ted. Tl:10 ga.mma-i-•a;fs of other wavelengths tJl l l continu0 on t;hr'ou .~-:; h the crystal. In order that this .,., ..,, .. The connection bet·N een wavelength. and ang le of incidence for B1~a; g reflection is f:1;l vcn by (for first order reflec- tion) '}\ • 2d sin e where )\ is the vrn.velen1,;th in centimotel''S, and d is the spac ll1t; of the atomic planes being used, in centimeters. e is t.iw a ~1;:S l u between the incident direction of gamrna-rays and tne a t omic planes used. If the boam is incident at an angle e the diffracted boain will make the s11me angle e with t he atornlc planes so thut i ncident and eme r gent angles are equal. Tt1U s the deviation of the refracted p ar>t of the be am from :tts initial direction 12 20. - 2 .. beam of gam11m-r c-J.JS whi.ch is not diffractOd by the crystal ;:ihall not reacn tho detocting system, a ;:;ystem of lead baffles called the collimator is placed between the crystal and the doteotinc; system. 'l'he construction of thls collimator will be dts cusaed later. Fi guPe l illustrates schematically the operation of the spectrometer. It s h ould b e kept in mind that t !1ts f.i ,;;ur>c is only schematic and d.lme11sions aro exa.1:i;gerated to ill irntrate the operation~ rrhe view on the left s l'1o·v1s t l1o s-o octromBter Ht · a. settin? .v :d.c h wlll 1,:;ive reflection from on0 sid e of t :- rn atorni.c planes of t.l:la quartz crystal and tho view on tho Pl g ht sho .is the settin1 for reflecti on from ti:10 other side oi' t ;,1e same atomLc planos. The view in the center s :1T.-vs the zer6 wavelength settlnt; , .in whlch all wavelength gan1rna- r ~y s will be detected by the gei ger counter. In order that the lead collimator and support ( wi'lich welgh nea~ly 1$00 pounds} ri,;;~ed not be rnovod as the Bragg angle is ci:1anf;ed, the spectro:m,J ter op era tes by rot a ting both tl"le soarco and t~10 Cl";/stal to maintain the lnc.ldent a nd emer• c: ;ent &.nglos the srur1e. In Figure 1 the focal circle ( which has e. J.1.arneter equal to the radius of curvature of the crystal) is shown although it does not ox.1st as such on the instrwnent. The source ls con ,3 tr·a1ned always to movo on the focal circle by tho radius bar SR ·ahile tho focal circle U;self' ( whose center is ut R) r·otatos bodily about the point P of its cir•cU111f e renco. '11 he carr.tage 1:3 p ivots about the point X which, along. - J d ith t i"l0 t . ivot point P, is fixed in space. The carriage C rolls a long B keeping always pcrp end:tcular to the bea..'11 PA.This b e am can slide thru carria~e C as necossur:r to allow the rhe carriag e D in turn roll;;; along the top above motion. of carr i age 1 c. Tbe distance DP is f :i.xed. Since the dis- tance SR is fixed B.lso, the source 8 moves on ball-bearing ways on bewn DP. l'he rnotion of the two car-riages C and D is deter- 1 mined by t·.vo lon,s precision screws l o cated in C ( one abovo t he othor) v1hich aro geared to -:se'ther so as to turn in oppos 1 to dL.re ctions a.nd which havo the same pitch anl same rate of rot a tion. ::.; crev,s. There aro thr>ust bearln6 s at the ends of' these Carriage C is moved by mae.ns of a nut fixed to B (ut X) runnin t, on the lower screw-. By means of a nut fixed to D runaing on the up per screw, carriage Dis moved the samo d ist ance on C as C is moved, on B. 'l1 hus t l10 ang le DPA is al wa y s eqL~a l to t l10 ang le Ii.PX. Each ,J f t ll0se a;.1 i ;l 0 s is equal to the Bragg an;ile de- f l ne d above. C, [,W rrhus tnc distance of ca1~riag 0 D alone; carriage measurod from tl'ie position .'.3ti,.lwn in the central vi e .v i.n Pi guro 1, is p roporti onal to the .sL10 of' the an;:~le D:?A. Fr '.)!'fl the l3ra2;g coni i !:;lon, then, this d.ist s.nce l::, .: Erectly p ropo :•tional to the wa vele11.,i;;tll bo t ng measured 1 n any . given s r:i ectrmnet c r position. Tl'rn pitcn or tho precision sc :r 0 v1 ls ;.; ,., ch that one revolution {whlch can be read to 0.001 of a revolution) moves ca:r rla{:) 3 D 1 mlllimetor relative to car r iage c. ;'J ith tht-) ) -- 4- - spac i ng of the atomic planes being u sed in the quartz crystal t h :i,.s one :l'.'<rvolution corres ) onds very ne a rly {111. fact to 3 ')u.rts ln 10 ,ooo) to a waveleng tl1 diff'eranc e of 10- 11 oe nti- mete 1"s 'Nhich is called a r'l illiang strom, The name 11 x.-unl t" is u.s t.: ally reserved for the Siegbah.l'l se a l<) and is i;t1er•efore not 11 10ce n timeters exactl y . The a ctual calibration of this screw wlll bo described later. f'i gui·e 2 sh0v1s two ways of using the t r·ansrni ssLon- t ;ype curved crystal s J ectrometer, of which the arrangement at the ri ght is used for measur.tng grumna-ray wavelongths . Figure J shows the fundamental geometi-•y of ti1e curve d cr;:rsta.l focusing spectrometer used in transmiss ion. Due to the fact t hat t he cry sta l 1s bent to a r•adius . ·. vhich is equal to the diameter of the focal circle thoro will be a eli ,5i1t aberx•atlon due to the failure of the cryst al t o lie on the focal circle as shown in li'igure 1+• 'l'he relative line broadening from this abe1~ration is g iven by (l) -- c.os e (\- cos "'J 4>) Cos(~+9) wh ere e is the Brag g angle and (\) the half angle of aperture as s hown in F'igure !.1.• .. 5 II Comoonent Po.rts of t i1e: :J ;)ec tromo ter 'I'hc soarce of ra.d lation f -n · t;:10 :3p6ctrometer is in mos t c a ses a tn5.n stri r, of m.~ t e1~ial of from U.10 inc h to t,1i c i{.:10 s2 from 0.001 O.~S inch de p ending u p on the absorption in ti:i.e :sot:.r ee of' rad:La.tlon b e inr; me ast.ired. In the c asu of ~uurce mutdr'ial itself onl y- a mucn smaller d ep th of t ~1e source on th e si d0 facl~~ the cryst a l and count er will ba effectlve in emi t t; 'L n c; g;a:nma-rays wnich can be measured. 'l'~ie sou rce is ;1laced on the focal cir·cle so tha t .sourc e l;e or;ic try ,·r i.th thG ~hieldlng n e ces sar y . l eust 4 1 ' 'l'here are at of l ea.J s u rro undints t r1e s ou rce except ln the f o r- ward di rection. The bottom part of the source shield sits on a metal p l a t e •i fbtch r ol ls on a uoti1a r p late f a stened to the boa.r:i b ;'f :lk:: ans of ball b earin ~,s in h a :edened tra c k s. 'l1his i s p r ::; c1.s o l y made s0 t ha t a s the ~p;;:3 CtI'onw tor moves, t he mo tion of tne ;:;o urce aloni;, b ·0 am P.0 ( se e 1i'i gu 2'a l} is v e ry a c curat ,~ l f in a hoPizonta l p l ane and in t he raJio.l d Lrect ion. As shown in Fi F_;u r o 6 t he so urce is p laced in a hol d er ..vn i c 11 holds 1 t uccuru t ely v e rtl cal. ti:1L::, 'rhe slopln;,; ja:,vs of f1o lde r {i n to wh Lch l ead is mo lde d ) mo relJ llmit t t10 llltlximur:1 i iver•g ,:;nc e o f tne be am of radiation. define a source slit . Tt10 J J,o not The entire source width omits radla- tion into t he c ry stal a pe rture. Th i s sou rce nolJe r mounts - 6 on a circular' dis c whi ch fits into a disc ::.;haped hollov1 in the lo -, :er l1ornispi1ere of ttlf;;) s ourc e shield so that adju~tm0nt ma; bri ,:u:1d,J to :Lnsure that t ,1e source is looking at tue. cry - stal str Lctly edge on (so as to minimize its effective width o:·1 the focal circl e and in.sur-e op timum resolvln;::; power). Tn0 surfaces involved are suff :lciently accu.r>ately ~,w i e so that 1 t is p ossibl. e in th0 follo .,v in,\ way to insure that t i:1e s our•ce stands acc uratel y v e rtical. "rhe lower homi- s phe re of' the so u rce shield, which has i t:s top a nd bot torn s u rfuces niac ::-1 l ne d paral lel anJ s l ts on a plate that moves parallel to itself is made level usinJ a p recision level, so t .crnt its. top surface li es in a horL zont a l _p lane. 11 h us when the so u r·ce holder l$ p erpendicular to this s u rface, th~ slot t~at tne source fits i nto flill be ve rtical~ •~~ ns c es- sity for ge tt l ng the sourc0 strictly vertic a l arises from t he f uct thut t~ e easiest way to have t he source parallel to tne generator~ of t1:1e cylinde r arou nd w11lch the cry-stal i s be nt is to have U1em bot h vertical. t 110 cr; stal hold or will be s een later. B. Golli1~ato r Ho~'-i t hiB i s do ne .on I n or de r tnat t he i iffracte d radiat ion may be dot o c tod v-.:it {1out int{~rferenc e from t i1e main beam of rudl.atlo n rJhl. c ;1 i;oes directly throu bh t ~1e crys t l'-1, a s y ~tem of l e ad baff l 0 s is rn, cos sary. The ant; le oet we en tho diffracted r r1dlation c.:md the tra nsmi t;ted radiation i:.; t •,•iice the Bra:,:;g angl e for th::l t rad.tation b1..~t is still a s mall angle. For - 7 ex::-.un:Jl e , this an.,3lc be t ween main. and d if'frac ted be ams is ab ou t 41+ mlnutes of arc at a waveleng th of 25 x 10-11 a t~a in, tno diffracted radiut:Lon alwaJs a.ppe i1rs to ori::;inate at t; t1•a po.int called V (virt u al soul"'-c©). Thus a system of l e ad baffl e s ,r;hich w::>Uld pass ra.dia t i on c omiru6 from t h is pQint a nd no other would pass tt1e diffru.c ted beam. In pre- vi o us \mrk ·c his baffle system, whl cn we shall call t.he colliw a tor, con::$isted of'/ tapering lead sneets with 8 tapering open spaces. As the transmission cha.ract0 ristics of this co l lim,J t o r det (-) r mlne no w close t t10 instrument can be used to the posi tio :i shown in t :10 oenter of F'i t;ure 1, ( and r1ence i'10:;: short u g amma-ra.J wavelength can iJe moasured} l t is destrabl a t J b.ave the acce , tan.ce 1,, idt }1 as Siiictll as p o::,:::1ibl0. The improvement maJ e in t hl s collimator was affected as follows. A set of le a d she et~ 4 inches hi J h, front e nd to 0.050 inches at the rear end were molded of t yp e l.llotal { d.:.:/~ lead, 15 !o antimony and 3;;; tin). :Jeveral of t ho s o p lates v1er0 cut leni:;thwise to ·f :::,rni narro v;er spacers which were placed bet woen adjacent partitions at the top and bottom so as to form an arr- an,y .iment of 25 tapering plates and 26 taper.tug openings. Tho front; and back ends of t I·1 is C(>llimator are shown in I<,tgure '/. Tho front op ening is just s li t;r1tly larger than the crys ·t a l aperturi., and t he raar l a r g e ono u 0h to include tho urnb1• a 1.1.na p enumbra in the - verti c al dimension. b inc :10s ben.tnd (j .. The front of the c ollimato r is about the crys t a l. Tho tar.1er of tile le a d ;Hirti- ::;i:ins is snc h t hat the collimator a ccepts radiation from a 10int (actually all points on a vertical line) -:1hich is the f'ocal di stance of the crysta l plus the. above o lnc,ws from t i:.e c-!\Jstal t o the front face of the collimator. 'rhe tr·ansmission cu rve of' the collimat or has the Bh a po sho,·m in Pigure 7A '~vtien the spectrometer ls moved across t he central p osition. Tho wings of this curve extend for quite a distanc 0 on both sides beyond tne point of' cut-off defined by tne ,seomo try of th8 device because of sca cterin6 fr-om the collimator p l a t o s. Tnis curve ind icates ho w the backg round incre ase s as the spectrometer a.pp1•oachos the zero wa.v eJ.ength s et ting {i.e. h i g her energ:t es) • .l?rorn tho curve it can be s 0en t ha t t r1e bacl{ground .1ou l d b,)sin to i n crease up:pr0 ciabl y at wav o le n ':; -ths shor•ter tnan 3 x. u. ( E-)ne r e;tes 6 1.. eat.e r than 4 mev). !t is estimated tha t it c:i fill not be feasible to me asure wavelengths shorte r i~:111.n about }_~ x.u. (2 to 3 mev As described a bove this collimato r should tr a nsmit 50 /; of the radlatton fall i n ;;; on · tho front ope n ing slnco t h e O'Jd.n and closed ~paces ar•e equal in wi:.it:,h. In assemblin.i~; t he collima tor it was f ound that thE~ surf'a ces of the molded Jlat e s •.vor-o slightly ·/;;av y , and an;r i rr.•o ;:ulari ty of the su rface to ~lds to c u t down the o pen ~;;pac e a v ailable between ad jac ent i·;lates. i.:::v eI•y 0.t'fo:r:>t wa~1 made to eo1~rect s:..:ch defe cts d.uPi:Qt; t l"1e asuembl y . The transmission of this col- linrn.t ::n"' was moa[rnred uslni; a radium n.;cdlo as source of r- ad l:l'cion and an apo1•ture arrnngome nt so that the radiation cm,. J.d bo measured both ·11i th. and. wi th :) t.l.t t ho collimator in t h0 befu'1t. The trahsmlsuion was found to be cq:i;:,,r•ox L:m atdly 35,t, so th,~t of the number of gamrn a-ra:.rs uiff'racted lJy t h e c2ystnl onl y about 1/3 are achni tted to the ;~;eiger counter. It should be pointed out that this collimation cfoes not affect the .::.;;ectral re::.;olving power of tho instrunwnt, for that der;ends on the foco.l i: attern of t ne curved cryst 8.l . 'I'ho collinw.tlon taires place after diffraction by the crystal. C. Cf_Jst sJ_ and ff-ilde r In l:"lgure d is slloun the arr>an,:.;ement f'o~ nolding tje q~artz crJstal against the c y lindrical surface of~ st a inlos ,.:; st;Jel i)lo c,{. Botn the convex and t;be concavu sur- facos on ti1ese blocks ,vet'~ ,~J;round to t ile CJlindrical prof'tle by a m0tnod wilt c h has b e en descrlbect< 2 ). Tnis is done using a surface g rinder , ,1th u ji g wr1tch i nsu rt:1s that ti:lo genorat ors of' the cylindrical surf a c es s !1all be accurately pePpe :ldl c11l a r to the precision ground top a nd bottom s..rfac o s of the s'c eo l block. After tsrin:iini.5, tn02e blocks with the apertt::.res in t i1em as shown a.r•e lap ,.i ed by i1i:md against solid oast iron bloc ~rn ,inos0 c c. r•ved surfa c es have been prepared by the same S',H•face gr inder method. 'l'h0 la;n Lng ls done in a ;}arallel ftxod blocks are ahmys parallel . T::1is insures pa:eallelism - 10 of the go::.w rat ors of' lap and crystal holJor. will remaln cyl~ndrical. Thus the s h ape The concavo lapp ln,:; blocl-r a 6 a inst wht ch the conve.x s urface of the crystal h older is lapo ed 12 checked for excellence of focus P ':: riod:!..c ally. This is done b J using a slit source of li bht -and a miscroscope at the focus. 'fl1e focal pattorn ls observed and wr10n this pattern is suitablJ .narrow. we have found that tfie crystal holder itself ,vill bo as good as the lapp ing block. rhe crystal ls the n i n serted and bent to the cylin- 1 drical profil e and :l,ts c,oncave surface tested oritlcal ly. Only the convex memba:r· of the crystal holder· determinos the curvature of the crystal by intimate contact thore with. A rubber gasket is placed bet we en the back or concave me1nber and t he crysto.l. 'I1he pr oceJu1°0 of / ;ettiri,; t i:1e cryst a l bent against the c y-llndrical surface ts a difficult one since the smalles t s p eck of' J,.st or ot.; 1er foreign matter on eit.t1er surface will prevent t;be crJ stHl from contacti:n6 t he s teel u.t ev'.JrJ point and t£1us ruin tho accu:"ac:r of b0ndln6 • Por- tuni.:,.te l y t:nls situation is eas Lly detected becuus , of the 0 ; inte:r•fe r ence fringes betw den t he })Olished s Lrf a c e s of the cr•ysta1 and tl"w block. The convex or• defining member of the crystal holder is p rovid,a d ~·; 1th ribs . which croLlS the g a mma- ray a per ture to afford betfer su p~ ort and deflnition to the bent cryst a l ,ihereas the concave r iernbe r has an op 0m hole. The int c:efac e bet ween tne cr,yst i:i. l a nu t n e ribs is clearly visibl e tI1rough t r.1 ls hole. As tho cry-stal is berit bJ clamp- ing tno back piece ( concave surface) agai.ns t it, ti1ese - 11 - frLn 0 es cun be observed ( t .:1.roug h th0 apertu re in tl1e back block:) to spread out and tho effect of any particles between tr.e tv;o surfaces ls immedtately notlced. Tho cleaning process consists of brashing tho surfaces with a cam0ls hair brush. Sinc e trie crJ s tnl will charge u p when :t t is brushed and will p ick u1.:• particles from the air, this bru.shi.ng was done in tr1e p rGsE.ir1co of a woak sour~e of ga-rnrr1a.-rays ( namely co 60 ) • Nhcn the crystal 118.s contacted th<3 metal block over thd whole width of ap,~rture, as evidenced by the frifl(;e p a t tern, the focal pattern of the polished faces of the crystal is observed wlth the above mentioned optical set up. '1'hi!:l of cour'se does not tost tl10 focus of ti'.le atomlc planos afj used ln the spectrometer but will give a good indication of this if the S[) ecimen :ts a r, cr•fect monocrystnl accurately cut ::1.s sho wn in Fi gure 9• 'ro test the focusing of the various regions of the bont cryst a l optically. a mask was placed in front of the cryst ul. Tr1io mask contained 5/16 inch diameter holes in a hori.::ont a l llne .vtd.ch could be iJlaced over any of the 3 llper•t:J res of tL1e cryst u.l holder ( see again Figure d} l-c0 0ping t h e othe r two covered. This gives five lines in the focal pattern as seen in the microacope. These five raJs can be traced through the focal plai1e to Jete~rrilne J:1ow neaI'ly tb.oy all meet in a polnt. Pirst t heir separati on is me a sured {with travelins eyepiece of the microscope) ahead of the focus and t t1en behind the !"ocus. The patt01~n obtained for the central aperture· of the crystal holdor• is sho ·,vn at tl:i.e .. 12 top of FL~ure 10. The 1Jtvttern fr•om tho other two a por>turos is similar• anJ overlaps . tr1is nea r ly exactly. From t r1is i t ca:1 be s eo n that at tho position of best focus t he focal p a t torn is ab out 0 .06 millimeters wlde (correspondlng to 0.06 x.u. on spectrome ter). To detennine wi1ether or not the atomic nlanes are parall •,'J l to tho ,foner&t()J:'3 of the cylindri cal surface ti1e spectr•ometer ls t.tsed as is t,i1ovm on the left in F1l gure 2. 'l'ho crJs tal in its holder 1s set up ln place on the spectrometer \vit;h the conte1.. of t::1<1 crystal above the p ivot ;)olnt P (see Figure 1) and tho holder is leveled by means of a p recl- slon l evel. (The p ivots of the spectrom8ter have all been p revio trn l:1 render>od exa.ctl,Y" vertical by mea.,s of' levels.) /1.n. x-ray- tube 'Lllumi na'Go s a fluorescer p l ~.w cd ns at A in Fi f;u1·0 2 anJ. on a piece of film th8 K spec tnan is r,:;corded on both ~ides of t he centra l p osition {at the corroct p ositions to recei vo the J{ qi&ctrum of the fluoresco1"). If t he at;om:tc planes l::i rB n ot vertical, tho spectrum on one side w:tll be lower on th,,:: .film than the s p ec 1: rum 'taken on the othe r• side. iben th{} p lanes are v e rtlce. l t £1e s pectra from eithe1~ s id0 will be on the same horiz.ontal line on the film. To facilit ate this test t tw lon;\;th of the vert,ical spectt"llm l:i.ne iu made V ·.H'J S •:10:r>t by a lead apertll.r'G stop placed at th0 crystal. Th0 tent of' the focul pattern of the crystal as it is used for t-nc spec trorne ter is made ,,1th x-r•ays. A tungsten tm"f~Ct x-ray tubo ls plac c) d on the ::;pectromet e l' with ttle - 13 tar\_;ot dirdctly b o bi.nd a slit at . the source positior1. Thie s lit i:, n r.i.de abou t 0.001 inch ·. ,1ide (0.025 millimeters} and t~a 1nt0~sity from the x-ruy tube ls sufficient to give a co nvenient counting rate in. the detector wr1en the spectrometer is set at t Lie posl tion cor-res pond:ti'l['; to t i.1e wavelcnt; th An ape :rotur·e system is of the K ~, line of the tuniJ stcn. placed in front of t ho crJs tal ';,ihLch perm its observation of the focus of eightoe t1 d:l.fferent zones o.r the cr y stal as sho wn in the diagram in Figure 10. 'rhe po s 1 t ion of the Kcc. 1 line of tungsten is deteri.lltned f or each of these sections of' tho cryst u.1 and from the lmo im posi tion of the a pertuPe, a ray may bo corw t ructed from tl1at zone of the crys tal. 'l'ha actual p attern obtained is shown in tho lower p art of F'i gur•,a 10. rr1is is u sup erposition of · ra.rs from all tho 1 oL,;hteen zones of the crjs t a l. for th;;:H:H3 The position of tho slit . me asurements was a lon:~ t i10 .:1olld lln::} flhcY,;m but it mJ.s d0ter•mlned f'1• om this p attern ti-1at the best focus would be t; ,,;o rriilllmot ~n·s to the re a r•. Adjm:..tment of this dtstv..noe is p o~sibl~ and by this proceJuro one obt ains tho host place to locate the :1ource. It can bo seen that t h0 focal pa ttern is 0.07 x.u. wide (0.07 millimeters in space). It should bo kep t in mind that distances left and ri ght :tn the fi gure a Pe exai1;0 erated a hundredfold. f'ull slze. The c1~ystal a.per·ture is s hown 'l'l-id c ,.,mter ;11vot foi.• tho focal c1r•cle (R in P l f;ure 1) is t1dj t; sto.ble and :1.s set so as to be half \10.Y be- tween t he cry st a l and the b ,::i st focus.. made to ± 0.001 inc he s. 'l11-1is adjustment is ... 14 ... The crystal used for the tantalum measurements and the January 1950 gold measureme nts was 2 millimeters thi ck as compared with a. l millime ter thick crystal used previously; It was feared that this thicker crystal might crack after be.ing bent but it did not do so, The edges were carefully polished and rounded to remove any nicks or scra't;ches where a erack might start . A detailed study has been ma.de of the reflection properties of these crystals by Lind, West and Dlilllo nd ( 3 } w D. Geiger Counter and Cosmic R.a.l Shielding The detector for this sp ectrometer is a geiger counter in which it is possible to c ount a certain fraction of the gamma-rays passing through it. The shape of this counter can be visualized from Figure 11. It has a square cross section since the diffracted beam of gamma-rays coming from the crystal and passing through the collimator is nearly square {it is rectangular due to the penumbra). The efficiency of this counter for detecting gammarays 1s increased by placing in it plates, s p aced every ¼ inch of its length, in which the gamma-rays may eject electrons by either the photoelectric effect or the Compton effect (above an energy of 500 kev) o It is these electrons which cau s e the count pulse. A representative counter is the follo wing one which was used for the majority of the tantalum 182 wavelength measurements . The p lates are copp er,. 0 . 005 inch thick each with four½ inch diameter holes for the anode wires . There - 1.5 are JO of those plates. The anode wire is 0.002 inch dia• met e r- tungsten wire which ia fed throu 6 h Stupakoff insulators at one ond a ~-id do-.vn the center of t l10 holos in the nlatos. At the other end, and inside the counter case, the anode around tNo anothe:r• S t'~ t of holes. rod l~aulators und back throu gh Thus only 2 anodo ,d;_·os ar•o used, each wire golne; throuc~ll two sets of holes. The alum.lnum Nlndo 'N on the fr :_H1t end of' the count ,3r is sealed with a l::HiJ ;;;asJ.,;:et betw,.Hn it and the front flanged fa.co of the counter. .f'rmne 'l'hls wi r'> dow and gaskot are heLl do.v,m by a square v<✓hich is screwed onto the front face of' the cou:iter us shown in F-'igure 11. mixt ·.,re as fo1low:J: 'l'his counter was filled with a gas 5:/I, ethylene for· a qu ench gas and. 95;; arcon to a total pressure of 3d centimeters. has a plateau f;r-om 1160 V to lL~OO V. This counter I t has b \➔ en o ,-.ernt tng ~1 t nce Ja.nuary 1950 and still S'.~oras to be working satlsfactorily. A large number of counter:.,; of thL: type were bu i lt before u succe ssful one was obtained. 'rl-10 difficulty wi ti1 Uw unse.tlsf'actor.1 ones was that they would g ive multiple pulses and within a day have no plateau at all 11 eYen tl'10W_;h t he.1 wore not used for cou.ntin 6 • It ,vas our op tnion that tt was tl1e cathode surfacs that was causl.nl;; the effect. Lead :-)la.tes and tantalum plates were t1.,ied but neither woLild pr•ovcr:1ent could bo noticed but t t o nly pro1on,sc➔ d the-tr life b;s,r a f ,0 \'J .Jay s. Unfortunately the r•eason for' the success of - 16 .. I~s prepar>a tion was in all e:3sential res pects t ~iat ·.rn • icno .-; or identical to . the ;) r ep aration of tho u.r1successful 0xumpl0s. ,rr eB.t c e.rc as to cleanliness in a ll cases was observed. In order to reduce the back 0 roundcount ing rate, the countel" ass ;:imhly ·Nas ;)urPounded by 1.¾- inches of lead. •. on a ll si des as a protection from local rad iation. To reduce t he cosmic ra-;:; backg1.. ounJ, t he count er 1s surrounded by a set of r>ectangular co1.int0rs completely sur•rounding four• sides. of -che g:si.1r. ma-ra y counter which however do not receive any of ti10 ga.'1u,1a-1~ay beam comi.ne; t l1rough the collimator. A cosmic r•ay vii1. ich pas:::;es tt1rough the mcdn counter wi ll also pas s t i:u•ou r;h one or more of thes e shielding co1..u1teI's and by .means • of an anti-coincidence circuit, a count in the main counte~ is not re gis tered if it is simultaneous with a pulse fr-om t .b.e shielding counttn~. 12. This arrange1nent is shown in Fi-g ure Bocuuse these shleldlng counters arc in anti-oolnoiuence with the mo.in count er the;r have come to be rofer-red to as anti-colnctdcnce or 1tA. c. 11 counters. These counters have reduced t he bac l{;.;rou nd counting Pate by a factor> of t wo. '11 hG bacl-::g:r•oitnd CO i.1nttng rat e with no source p resent w.ith tho count er' d e s c1"ibad above fluctuates around a value of about 80 counts pe r minute. Al thoug h 'c he counter is self quenching, a. quench • • circ uit :i.s usod, - 1·.rhich acts au a puls e former and f oeds into the scaler through the anti-co l ncl do nce cl:r•cu1 t. clrcul ts m•e s h o wn in Pigur<3S 13 and 14. These - 17 - The wavelength scre,'i is t he one whic h o'.l Nes car'ria s o D · r•olativ0 to carriage C ln Fl guPe 1, and · displacements alorle'.; this screw from the z e ro waveleng th position are strict ly proport.i.o :1al to we.v o leng tho AB mentioned before, each r civolution of this scre w c an be read to 0.001 or a revolution by means of a n accura:tely divided drum und v e rnier The desi ,:•;n is such t ha t each r·evolutlon of t: l1.is indicator. scrc':v co c res ponds quite clos .:l ly to an x.u. of vmvelength and so the sp e ctrometer is capable oi' g ivin6 r eading s to 0.001 XoU• Tho c har a cteristics of this wavelength sere~ were c l1ecl{ed by a com parator metnod. A fr a:rne holding a National Bureau of ;:jt :1,1da1"ds calibrated g lo.il:., decimeter scale ·ui th a tot a l interv a l of 100 millimeters was fastened to carriage D ( s ue F'i gure 1) and a viewing microscope was fastened to carriage c. Headings on t ho dec :Lme t 0r scale wero conp ared with t he re a din i;s on the scro·,u drurn as carria:Je D nas mov8d :~e lat.tve to C b y t urning the scro ·.v. These re ading s were t,"".k:en over a r·egion of 600 screw r•evolutions (,300 on each slde of center) and a calibration curve d:pav:n for the wavelength sere r, 6 lvln3 t ne correc tlori to be ap :,lied to a so r ow read ing 1.n any sp ectrometer posi 'cion within ·th.is Pang s. It ls used. to isive the corre ction to ap p ly to the dif fere nce bet-.:ieon -t wo different spe ctrome ter settings . ~1thin each revolutlon t he r0 is another effect which we shall call the p er Lodie effect, w:Li.ch indicates tho variatLms from linearity \<:l t h in - 18 one r e vol :It.ion. "r h is p eriodic error •;ias chc cl-{ed also by usj_nc:; t his d e c i me ter scale, but only every dOth rovolu:tion. 'l'his correction does not vary ap ;,1,ec'i.a.bly from one revolution. to another , but a t;:r•adual change is no ticed ovor many revolutions. The1•e is one more correcti on to be taken :lnto account. The 3ourcc is situated on top o f the bo am PD {Fi gure 1) which places it about 1~ ln.cl1es above the :rselfali g nin,;;'' ball bear tn 1_; s by m-@ans of which carr iag e D rolls on c. The dri vo for carri.a,'2:e D is the n u t riding on tr1e waveleng th screw ·.-, hl ch- is belo w tho ball bear.L n !~ Nheels of 0. Thu s any irrol!,ulari ty 01~ ecccntrici.ty in these ball bearlng ,vhoe ls or minute [Hl.rtieles on t :10 tracks causos a mo tion of the ::Jourcc relat;lvo to the p osition it iiould have if t l1e c a1'riaL~e- D moYed N i th no tilting. 'l'he readi ng on the sere ~ , then, may not corr0 spond exactly to the position 01' the source. • To correct for this, a precision level was ;)l a ced crosswise on the beai.11 durinJ the calibration men.ti •- )nod above and l ts road lngs taken an t he screw moved along. 'l'lli s g1. ves a referenc€, level I•e o.dl.ng to go vr!.th tile calibra- t ion curv 0 f or the serew. This level ls kept :tn pl ace on the bo rnn o.nJ Pe ad ln,,;s taken duri nL ·;'u.1.v elen6 th measu r em ents. 1'he difference in level re ading s at 2 spectrometer scttin1.:,s is compnre d with t he l e vel difference bet,.voc:m the s ame t trn se t;ting s durln/ t ~1•3 cali b1,.,ati .J n run a nd a correcti on a p plled on the b a si s of t hls, sinc u kno ,v tn the d istanc e s involv-3d , tho ,lispl a c 0m,,:,m t of the .::.\ou:cc rj may- be g ot t :)n from two level - 19 reading s. Tho magnitude of .t i1is co r·re ctlon wi ll l ,rt;er> be s ~e n to be of the ordQr of 0.010 x.u. in soma cas es . be either a p ositive or ne gati ve co r r ection. It can IV Abso1fil_g Ca.libratton .2.£.. ,vavele11gth Screw The above coI•rections 0 ive the devie.tlon.s from lin eo.ri t-:[.. of tl10 screw bu·t the actual conversion of the mJ..mbcr of ( correct,ad as above) screw r•evolu tions to the .l:i'or tnls the x-raJ tube with a tung st en tE.rJot was placed on the snectrometer with a s lit at the source posi t ion. l1dadl n 6 s wer-e taKen to determ i ne the sc:i:~ew positi on of the tu ngsten l<:q 1 line. ef3tab1.ish this. Several 5. n d.ependent r•un.c; wcrf: rnade to This Vc."'1.lue for> the i;w:1~c)'3ten K~1 line wh:lch L, no v; in tt-:irms of corrected screw· revo lu t ions, is c01n ) ar0d with the acc u rate waveleng th moasu1~om~nt mad('3 by i::8st0-t-) with u tvrn crystal spectromete r in thls laboratory. Tl'lis b iveu t rie f ::i.ctor by wi'1tch th0 screw revolutions must be multi p lied - to give the number of x..u. · wavelength. This 6 1 ves th0 wuvelen0 th in terms of Sieg bah...'1. waveleng ths and must be correc te :1 by another factor to (;.;i ve the wavolenc.;th in. millin.ng stroms or contir(10te1~s. Th is latt,3r conv cn."'sion c an be obtained from r ,:::ference (5). ivo.v0length meusuremonts me ter us f ollo wo: aP0 made on t lw spec tro- Gount.Ln;·; ri'.1tos a:ee taJrn n for a given. increase wi ll be se en when tho ::ipo c :~:r,:'.:lme tor setting car-res- .. 21 ThG wid t h of this l ine profil e di ll ba discussed belo ~. Thi s p:rocedure is re nea ted on t rw ot he r side of zero so thut t wo li ne p rofilos are obt ainoJ which ai-•e a distance apa.!•t co :::•rusponding to t wice thetr -w avelength. This eliminates tho necessity- of knowin6 exactly the zero position. The differcn.ce betwoen t .t10 S) ectrometer rE?a.dings a.t these two lino profiles is corrected as above to give the t1~ue wavelength of the radiation. V Line d idt.hs The instrur:m ntal ca.uses of line broa.d.onl ng a.re (1) the geometric source ~ddth, (2) the int1.. insic diffrac- tion pattern character•iatic of -the quartz crystal, ( J) the focal aberration due to the failure of all the crystal to focus at one point. Z ')Ues of' the 'l'hese l a tter two aberrations can be determined f'rom measurements as in l~i ,;;uro 10. The s J0ctral dlstr•ibution of the radiation has be (;,11 approximated in only one case ( 6 ), for the ann.ihilation r a diation fr,om cu 01 4-. In the case of most gamma-ray sources the natural line breadth is too narrow to, be resolved .J y t t:1.is instru;.nent. - 23 - s pe ctromet e r f or 2\ hours a day, ,: ;h:i.ch J.,:3 very imr,ort (-.,_nt for short r1u lf 1lfG sources an arrangement has been devised for ;:mt():nat;i_c :.;.lly trddn.;; readlnc s and advancing . the sp r;ctrometer. r::1is Nas bull t by J • Kohl. 1 1 T.i1ls a.utonw.tic ob!:rnrver wJ.11 accumulate the counter ;;ulses fo1' a preset time interval and at the ead of this interval will move tho spectrometer to the next posi tlon which can be preset in advar1ce according to a pr0d0termi.ned schedule. The automatic observer prints the accu:.:iula tGd nu..."l'.lber of counts tog eti.1or wl th the time and the spectrometer setting. Tho accuracy of tl."10 spectrometer setting ls J.etormined by a gold contact riding on a seg- mented disc fastened to the dr1..rrn on the wavelength scro,1. 'l'hi..a se :'.;nented disc has 50 accurately dlvidod slot8 <r i1lch are filled wtth insulating material. The bold contact, tl1en, r>ides al·te1"'natelJ on conducting and insulatln,:': :3ections. Thf, contact and disc are ;jO connected that the motor driving the spectrometer will stop w::wn this contact passes from a conductir16 to an insulatini. ; section if the preset pro,;ram indicates that lt should stop. 'l1his prot;rrunin1:,; is done with a microswttc h riding on 16 millimeter m;vie film. Each timr1 the e;old contact encounters a co nductln2; section this film is advanc0d a L:;iven amount and if a hole has been punched in tt1C film so that the microswitci1 opens Nhen the film a dvances, then t .h e spectr-orneter ·,vlll stop when the - ::;,!, <-<+ - go1d - oon:tact rides off' tha.t conducting section. !) OSi tLms So ·the at which the sp.e ctrometer s.tops can b~ preset by punchlng a ppropriate holes in tl'le film .w hich passes undor the rnlcroswitch. The timing circuits are .controlled by a. synchronous motor \'Jhich closes a microswitch for a short time interval every minute. In -:1 esi;;.ni n6 multi-cellular ;:~e l ,~;er coun tc:cs .i.t i !'! ds~L-•able t o c h oo se the thick ness of t ile 1)l e..te s s o a s to g ive ;)iaximum efficiency for the energ y of gamma-rays being measur•ed. A counter d c ~i 6 11ed for a 6 iven ene r gy garillna- ray will be use ful for a range of energ i o s on either. side of the desi gn energy. Ho wever to cover the range of energ :les which it is possible to mes.sure with t he spectr ometer several g ei 6e r counters need to be employed. i\ set oi' t h r'oe counte rs will cover t h e range of 13ne r g ies if they are designed as follo Ns: 1. Co unter des i gne d for 0.7'-;J mev which will be us e f ul from 0.5 mev to 1.3 mev (f) 2. Count e r d esi gned for 0.2 j mev which will bo us ~f u l f r om 0 .10 me v to o .~ mev k ev An add i t l.onal c ounter wou ld be ne e de d if it was d e sl r ed to me a 3ure en.ergi os arou nd 2 mev. c ounter"(::d so f o.r. ·done of th0se have been en- Th e counter for ene :r-gi e s lo w·er than 100 kev is filled with Xenon s ince for t he se energi e s absorp tio n in the g a s is larg e und plates are not neede d. The de sl t5n of t 11e count e r is aff' e oted by the followi ng co:1sld0rations: 1. t h e material of t he absorbing p late s (for convex•sion of the g amma-rays into electrons) 2. the r ang e of eloc trons in this mate.i r i a.l - 20 - Jo tho gamma-ray absorption coefficient of the t::.aterial The nu:mber of plat!J s used and their tl1ickn0s s will be determ:lnod from the above. Tho lengti1 of the counter case and the minimum possible s :'.laclng between plates wi.11 determtne tho maximum ;unnbor of plates that can bo g'.)t ten i.nto the counter. The len,:;t:;h of the counter case was decided to be a.bout B inchos (FJ. ~~u.re 11) and the m:tnlmum spacing was set b,y the 1/J+ inch S)ace .r s. The thickness of the ;) lates for optimuin ef flcicncy should not be g1•eater than tl10 rang,3 of the g anmw.-ray secon- daries produced in the mate1•ial and in fact, as is si:1own later, the t l1lcj.cness should be sllchtly less t i:1.an -t.t1is rang e. T11e most comp lete data available for the range of electrons is that for t l1e range in aluminum obtaine d from Professor ··, r -'i:.io,·,l .r V ( 5) • The extra;)olatlon to the range 1.n co ;., pe r was made by taking into consideration only that the range is inversely p r oport .L onal to the ratio(' Z/ A wher(.3 p is the density. F1or the extrapolation from aluminum to co ppe r (from Z !! lJ to Z :! 29 ) • it is fel'c that tt1ls is satisfactory- to the · accu:r•acy desired he.:•e. ( '7 ) n01 tler'' trDns in lead i f 1 t 13 gL ves a curve for the ran.3e of elec- deslrod to wort: wl ·t;h materials near lead. Table · 1 gives the electron ranges in mlll:tmctors f or several energlos. Flgu:r'G 17 gl ves the ral'lt2;e plotted as a function of e •J.ergy. The rang;es i n E,lumlnum ax•e talJ;en .from Profe ssor F'owl e r-' s curves. Tho range of g amma-ray s e condu- ri e s , DID duce d in aluminum refers to the thickne ss of absorber which reduces the electron intensity to o.o)b (down by a factor O ...f> -')7) . In the counter designed for use between 0 • .5 and 1.0 mev t l1e ;samma ... ray secondaries will be produced alrnost entirely by the Com')ton 0ffect. Ji'or• the energy range 0.1 to u.5 mov it will be a combination of the Compton effect and p.:.--wt,;oelec- tric effect. Since each plate absorbs a small fr•actlon of the gamma-rays• the lust counter cell ( after the bearn has gone thru 25 or 30 such :,,lates) sees a bean1 of reduced intensity. For tnis reason the plates at the r• ,:::ar of the courite:e do not give as rnany conversion electrons as the first few plates. If the counter contalned just one cell (one conversion p late), the maximum efficiency would be obtained it t his plate were made e qual in thickness to the ranGe of tha electrons in the :;1aterial for the energy gamrna-rays being measui-•ed. However ii~ th0re ure many cells the efficiency may be incre ased some- what if the plates are made less than t .he 1•ange thickness as shown below. Let the efficiency ( relat:i.v0) per p late be e 01 t l1e range of ttie electrons in tt1e material be H a.'1.d the ti1iokness of the ,)late be t. Let us call )A the linear g a1:i.ma-ray ab- sor:,tlon coefficient resulting l.n electrons. ciency pe r plate: Then t.i.1.e ef'f'i- clEo=fJ-Y: TZ-X X dSSvW\e (dssurn-Es eje(teJ elec.+r'ons) t ~ 'R di\ ~o +ovwdv-d i Eo~j JA-- ~->< k 0 ~ i}ow 1f t ~10ro is a total of N p l a tes (25 t;o 30 in the cou nter) Th.at t his h as a maximur::i c an be seen by taKing t he sl o;,e a s a rune tion o:e t whi ch g ives: ~ ~ (l+ZRNf- - N14t)e~N1<-t -I now Nl"-t is small (of t he order of 0.05) so we can v.rrite: 1rt : (\+ 2 RtJ ~ - N~t )( \.. N1-'-t ) - I ~ Nr,- t1.._- (-z..+ z RN r-- )t + 2-f< fort i R t h is ls less than zero and f o r t : O.lR (for exa-:n?l e ) i t is greater t imn zero. The maximum c a n be f ound bet wee n these values oft, as wi ll be ~eon in a s pecial c a se. ln cop pe:r• ls nearly o.6 cm-1 • 'Th0 nm:ib0r' of plates in t he co unt er is to be JO. 'l 'i:ie A ;)lo t o f t :n e equhtion abov e i:~:l ving t he r e lative 0ffici tn1cy as a func- From this it can be s uea that the p lat:0s should be made 0.16 rnm . tni c k . 'l'ho c o pper ;) lutes used i n ti:le counter wore 0.1~5 mrn . ( 0 .005 inc.ries J t i1lck and so would b8 most off'iciont an energy sllc~htly l e ss than '(VJ 1cov . tor .For heavier :mat -o Pials, 1 i \ .: 0 l e ad, wh e1'e the absor• p t Lon d.oef'ficlerrt is Lriigh &nd tho r uace of the seconda rles i s lo w, the op t;iu um tril~krioss and used s u ccodsfull.:r for t~11e t 2.ntalun measur0;.nents f ;·'o!n l SO ke v to 1120 1rnv. VII I ., avelo ::1p;t i1s •,.i-amrna- :18.ys FollowinF Beta• Dec a ·J of Iod_:1.nc 131 ""'.. • .. • • _q_ _ ci::: ,.__ FUdgo ·,: a~ used for those ni.:~asu-:ee:me n ts. ~ r 1_3l) r - - T1'1() io ·l :t n e VJ;J.s p re- ci:J i tated onto o..n alumirnJn bacl d.n..s t .:ms i'orming .a -t '. 1i n sou rce. cnrvc.l quartz crys tal was 1 mlllimete r t hick and made use of the ( 310) planes which wor•e 2)0.Pp0ndi.cular to t l 10 faces of the crystal slab as discuss ed previously. Table 3 0 ivos t he r• csults of the indivifual measurements before and ::ifteP COl'.'l'.'Gction for t he s mall errors in the screw and in the carria,se me c hanism of tbe instrument tance in revolutions of t he wa·Jelength scr~n, bc'l tween the centci•s of two c ,)m~J lete lino profiles• as roflec tod to the left; and to t he r1c;tit of the {Jl0 ) ;>lanes of the qum'tz cr:;-stal. '1l:;1is, divided by two and by the instrument scr(:; w conversion factor {1.00023 revolutlons per x-unit) gives the W:.i.V'e l eng~h in x-u.ni ts ( 0iei; bahn scale). ThL.i i s then con- v 0r•ted to absolute units (10-ll cm) in t;he column Ag , by means of the f'ac·cor A~/ ~S • 1.00203 and tho final column i; ivi:o ::l t he energy- in lrnv from t11e formula kev • (L:::39~.• 8 x 10 -11 )/ { A<3 cm.}• dhen these rn easur-::;ments were startud. only the 36~L lcev and 80 kev lines had b oe n reported. A.ft e r measuremtmts - Jl - ar1 ived contalnin~; a new disintegration scheme of F. ;;'i etz 6 cr 1 and ii, . )cutscl1 (l O) , showing at least t,vo add'i tional lines. in s p ite of conslderable source decayj it was still oosslble to obt s. in one ~;recislon measu:i:~ement of thls line. 'l'wo weeks later, 0,,.1e:m, ,}J oe _and Cook published(l l) 1~esults L'1Jicatin.g; four garrti:a-ray lines fror~ this sa'Tie sour•ce, gi v1ng a different dec [.;.J sci1eme. In both of t;hese c ases t i1e ',1ork was done ;Nith a r:iag netic Beta-ray spectrometer, U1e precis.Lon of the ener;,:y detorrninations bein6 probi:1bly of t.ne order of a perc ent or so . Th'.:: J.l (; h.er ) recislon of tl1e 2-metor focusing s pcctr·)rnete1~ offers an o p)or'tuni ty to test and discrirn.i.nate sc i 1eme~1. It is easJ to verify t hat the energ ies of the do and 2d!+. kev lines add U~) to e ·.;ruv.11 ty v;lt l:i. t.ciat of t.i1e J6l.j.. kev line to a part iu i.J..':;)00 :tJtlich is about the _precis1.on to line. The precision measures assiBned i n Table Jara based chl0fly on nos::;ible s J ste;,~ atic errors ln the calibr.,1 ti.on. of tho instrum1.3nt rathe1• than on the excellent ra in•odueibllity . T' l1e::;,e results then .J ive ~·t ro ng i) ositLve su ;:. oori.; to tu, t;i etzger m1d Deutsc h s c heme. 'l'nc [,.dJi ttonal 1 ines ~:ill be measured wne n a new source is ,n•e ;; iired . It ~as ~osslble to estimate the intensity ratios fo-:c t; l1es0 t :rrce lL:us .kno .vin.1:s t:n.e reflection coefftcient of the cr>ystal at t he different NRITc l engths and the ge1. 1~;0r co1:u t0r 0fficle :1cJ . D. B. A. Thls was uossible thru the work of (Je0 references 3 ru1d 12.) iJlnd . ,,,c asur-8 ment:J of the 1 .. 1 and ·)_.3 mev (}ruri;n_a-Hay Lines Foll owin;s Decay of Co 00 A source of Cobalt tr1 t i:1e f o rm of a ;-net al strip vms px•e ~)nred and sent to Oal:t !1ldge f'or irr-.:1diation. life of this isotope is S years .. and de cay is aH '. rhe half 'l1he reaction of p reparation follo~s: 11Co SV +or'l' --'>~2.,Co bO + Y (slow) i,S-ldr~ (1.sNi &0 )*-+ (3- -t-Y l ~ 1..sNi (oo + ~ ~:~ !'-1ev-) l An nctivitJ of jJ rnilli curl es was obtained and used for t 1w meas u r ,~ments . Por these mea::;ur0rr1ents a ne ·:1 crystal i1older ( as sho ,n in Vi i;ure o) wi t i1 much larger a p erture tnan the first was used. T~1e quar tz cryst al used mrn t t1e ::1a.ine as ;; ruviou3l.f ( l n m. U1ic 1{ , JlO 9lanes ) o h. 110w c ollimator was put into use c x>i bed e,n'.i is shown in F'igure 7. teristic is s~1own in Fi gure •Its transr:1iss:i.on cnarac- '( i\ . by r e fle ct ions from both silas of the crystal planes. Run 1 (not shown) was oxploratory in nature to locate tho 1.3 rnev llne. i1un c: sl10Ns the 1.3 mev line of' co 00 wnile runs 4 and .. 33 .. S s ~lO'ii7 both the 1.1 and 1.3 rt.l.GV l ines. In run.:~, a sin6 le 1 trn~ pI•oflle of the 1. 1 mcv 1 i.ne ( not !')l o tted) wa s also r•un on t t10 r:t ,)1t hand side only. 'fho source was tal~en out of its hold tH' o.:. t'ter run 2 to per-£riit ter,1porary stud/ of a sample of ,~ ld2 ~·a rec e ived at th.at time. 'Phe co60 source was then re- no t s ho wn) was ;uade to r0loc-ate t;h,J lines. Thi:::. removal and :.:•0p lacement Df U1::; Bou::•co accounts f ,:H' the slight shift in t :1e 13.ne ::' o t; 1 t Lons on the instrmn0nt ~cale, a shift co r>resp onJtn.g to a d:1.s :, lacernent of t;h0 ~1ource in the sou.Pee holder tl uns from the t.-Jo sides of' the crystal plr..:.nes { ·Nh :!.ch is u:rnd us e. t1easuro of the wavelength) is vory r'eproducible from run to 131.,u-1. tmslos of r•oflection in minutes of aI"O and also the dis p lace- t0 b e not e d th.s.t the lines do not occur a t exactly the sa1..1e readings on the t wo sldes. 'rl1is is because the zero on the waveleng th scre w :!.oes not coincide exactly .vi th the B;:;ta point (the ;-i oint on the focal circle to whLch the roflocting pl anes v,rould convor 0 o if produced). Tl10 or•dlns.tc scale ;:; for the diff01:'ent ru,: -1s aro l,.1.dlcnted by ntJ..h1bers givin,._:; clw total numb ur of cou ats obs e rved at oach sutti.ni:~ for' a standard counti n 1; 1ntc rv a l ·;7h.1ch was l0C0 seconds for a ll thG runs plotted. F'igu:t·e 21 sho ,.-.;s 3 mor•e r-uns tu.ken on the l. 1 raev: line alono. 'l'hi:.:i g ives a goo d iJ.ea of the r•0:::,ro d uc ibility oi' ths rn casur'.::rne nts, when the .ins trurrwnt i :::.i Nork ing at 1 ts brnt. :Pl guro 22 shows a Jetall of on ~ of the l l nes. Table l-1- shows the results of tbe .vavclon:,;th measurements of th,.:> t,,'o gamma-ray lines of co60 • It is to be noted. t.he. t le~rn weight has ba ,~n assigned to the 1 • .3 mev wnvelong ths obtHined from !;he exploratory runs 1 and J. 'I'his i~ becau:., 1;, these cur-vea were talce.a with a s.t1orter count inc~: interval than tbe rest, their primary ob,j ec t belrl.i.$ t o locate the positiona of tne l:i.nes sufficiently accurately to perrni t plannlnz:; 8n economical schedule o.f settinri;s for i:;he 1.1 mev waveloni.;;ths obtained in runs d., L~, and ~ than in the t hl' 'je lr)tn r vory· satisfactory runs 0, 7, and a. In run 2 the ·,n:ivel<.:mgt!:1 of the single 1.1 mov ltne had to be doter- mined by m0asurln 6 1 ts Jistance fron1 tho n0i~r1borin6 1.-3 mev line. Also ti'10 counting int u rval ln this cas •'j Has only fiv e mlnutes. In run !J tho rc were counte r troubles .v.tlich \'Jere not o xtremely sorious but sufficient to malrn repeti ti-'.)ns of sorn2- of tho readln g u desirable. ;jUCh Pe :; eti th>t1s required ro1Jerslnt~ ti:1e direction of t1,s.vel of the scre:, w ccu'I'iage to reach a p revious settir12; and then :)roceed.ing as before. It has been f'ound that suc h a procedure in . the middle of a run r:u1y r>esu 1 t in minute but; de tee table hysteresis efff)cts ahich may lead t o sma.11 errors in tne wavoleng th rEH1din,,;s. 'r.t:i.ere was u GUs :·) lcion also in run 5 that the beta -point of the instrument mi~ht have shifted ever so sli chtly in ~olr~ from the r 3flections on one side to those on tne other. measuri~g the s e~ ara ti0ns .f'. rcnn mcv lines. In th~~ casi-:; of run .,_ , r~r1 0 . ... .3 a ci. Jacen ,_J l . ~ S, it br:,ta .. ,1olnt sh ift; had inde ed occurred and therefore t~1is l!l lines togo ther with the average value of these latter 0ere usod ( instead of the se r) aru tl ·m betw e<,m right and left; hand orders) and only half weight wa:.1 ass i ,.:;ned to this individual value. All of these deviations aro small and give no cause for alarm re garding the rcllabili ty or the final avera 1.~e The 1.3 mev lino at 9 x-units is the shortest WD,velcngth so f'ar s tudisd wl th the s oac trorneter a ;:1d l t i·.-as of interest to measure the int egrate -1 reflecti on coeffici ~nt of tn~~ (310 i planes of the quartz Cl'yst.al Rt th18 wavelength for c rxaparison w:i t D tt1e data at lone;er wavel_engths. 'rl:ie total countlnz rate ln the dir-ectly tr ansmitted beam was dotermirn,d by setting the s pectrom e ter at :.:io t iw. t 11 zero wf.ivelen;_;thrr t he ;:rlmary beam i·ms dlrec tls transm:t tted throu ;-,; h t hr3 cr·Jsta J. a nd colllmator t ,J the cou.?1ter. Th is bean is far too intens e to b e me nimreJ by the counter directly, so it is ne e e 3.1:,:1t•y to intr'oduce absorbin1~ s heets into the be rm and plot the counting rate as a function of absorber th:Lci<ness ~1nd extrapolate to zero t i1ickness. One-httlf of thl:s d irect - 36 ti1en be compared -..vi th this central beam count1n,!; rt1te to . iv c1 the ..frfwtion of' 6 amrna-ray photon!.3 d.ii'i'ractcJd by the :~.97 counts 1:::i the diffracted beam pe1• 10,000 counts in the direct boam; 1;.,1d for t .he 1 • .3 mev line, l~.12 counts 1n the dlffract-sd :}Cam :;::,or 10,000 counts in the direct bemn. 'I'his does not ~lve the integrated reflection coefficient (see refe1.,ence 3) but it gives a basis f't'om ·,,l:lich the latteP can be calculated. The integrated reflection coefficlent has been shown to d:lrninlsh as )\ 2 for wavelent~ths from "It. • 200 x.u. to ~- 9 x.u. c. 1vleasurement of the 4:11 kev Gamma-R_al:.....E.ollowip.5 Beta Deca;{ of Gold J.28 {Aul JG) Prollmlnary results for gold nave already been )Ublished(7) but several sources of gold have boen measured st.nee then and the a.grecm0nt is very good. Gold is a voPy satisfactory- source for checkine>; the operation of the spectrometer because of the hi r)l specific activity available in sources irradiated at Oak Hid3e (5000 curies per gram for ~old}. Tnis mal{os it possible to get sufficient acti- vity lnt;o a source 'that is only J.001 inches wi.de (0.02;, mm.) with which it is possible to chock the resolution of the quartz crystal. The gold sou.rcos used wore iq the form or gold plating 0.001 inchos tni.ck on an aluminum backing. source ,vas 30 mm. high and 2 mm. deep. 'rhe ·rt1ls gives about JO mg. of 0,,old in ·N hlch an activity of lSO millicuries was - 37 obtcd.ned. Ti1e half' life is 2. 7 days. Ttw nuclear reac.tion i 1."7 d,i.t ~ ( So \-\9 l'IS)-M-+ (3--+ -V -~ maasurements. Tnis ra oresents measurements made on t~o san1p les of i:;;old, one in June 1949 and the other in January 1950. Tile measurements in June 1949 were made usin6 1.;he new colllmu.tot• and crystal holder described above and the 1 millimeter tnlck quartz cry-stal. 'r ha mcasu:r•ements ln January 1)50 were made us 1n1.; the 2 mi.11imet ~) r cry$tal. thick quartz 'l'his 2 millimeter crystal was fo u nd to have a r•,: ;floc- tion of 0.07;; at th.ts wavelengtn (i.o. out of every 1000 ::)hot.ons incident upon the crystal d. 7 of them underso Bra:!,g reflection). 'fhe ;f;ei 0 er counter used for• these January- 1,):;;0 measurornu n Ls was one comp osed 0f 25 tantalum IJlates 0.003 inches ti:1lck whicr1 ho.d be e n· eoJper ~lated wl th a thickness .of copper not exceeding 0.0001 inch on each side. This counter vms satisfactory only for a time long enough to obtain three runs. After this it bet,;an glvine; rnoru and more s purious counts. Tnesa spurious counta would coma in bursts as if tri/;,;ered by a bona-fide eount. Hcflllin.g ti1e counter v10uld not tmprove it at tni n stage of its deterioration. F:t e~ re 16 shows a t,Jplcal line prof il 0 obt ai ned for tho Tl1.0se two profiles re pr e sent one run, one profile taken in r efloctlon from one side of the (310) planes of the quurtz crystal and the other profile t al,:cn in r (;; flec- tlon from thu other side~ of .the same planes • . D. Check ~pectrometer Scr!'Jw Factor To check tlle spectrometer screw factor (that is, the factor ,'lhtch converts the revolutions of the wavelength screw into Sie gbahn x ...units), a slit was placed at the source ;)o.::;i tion on the spectrometer anri a tungsten target x.,.ray tube set up to illuminate the s11 t from the rear. In this way t i-1.ree runs ,iero made of tho tu.ngs ten .KA , x-ray lino with 1 t11e slit of the order of 0.001 inches wide or less. One of t hese line profiles 1s sho.n-i in l"igure 1.5. 'Pile spectrometer r•ea.d.lngs were t ~il{en and corrected in the usulil way. The corrected spectrom8ter re a dln~s (revo- lutions of the wavelength screw) obtained were as followsi Run l Hun 2 Hun 3 Averabe 200.6.39 200.636 208.630 208.635 scruw divisions From r of e r ,jnco !4- , .Vest's value for t i10 waveleng th of the tu.nt;;s ten Kat 1, line a.s obt ~1ined ,JL ti1 tho 2 crystal s p ec trometer is 20d • .575 ± 0.008 x-un.its. :: 1.00029 Thus tt1e scl"ew factor is screw division x.:.unitB - • Tne Vd.lue p reviously used. di.ff' ers f .Parn- this ~y only 6 p ar t8 in 100 , OGU . il source of tantalum in the form of a met:il stri rJ G.ooL~ inches thick, 0 .20 incho~ d 0 op and 1.2 inch-js hi ,_;h to 0 ,-:i.k iUcige for 5..rradiatlon for four months. '11£1e half lifd is fo'.).r months. Th.e nuclear reaction takln(; rda.cc is as f :)llows: I~ 181 1) II\ I + 0" --~::ai. iiA I 82. 1"3 (~\ow) V + () ~ 4 W\onth) . ( 14 w182}~ + (3- -t )' ~ 1+ w 1&1. + '6 ( W\Ol"l1) S')ectrum of tantalum ( ac t:.w.lly w182 } usin1s beta-spoctr•o1·1etors. See rcfcrencool4 through 22. The precision studJ of the ganma-ray s p ec tru,n sl1ould nw. k0 the sner~;y love ls .faiPly certain. 'I'i:i.e sample obtained from ~)ak f'-Uclge l1a.d nearly 500 mil.Licurios of l1i,:;i1 ener,_;y uc t.1 vi ty ( 1 mev). A aurvey meter gave 2·;1· Hoenti~en/hr at one foot. The three high energy l.:.nes were measured ftrst a nd trie results of tbe individual measur,rments on each line lines. Trrn ::.1pect;rum of' tno hlg11 energy lines is s .i1own at the to:) ln Pigure 23. ;jlnc:e the lld9 kev lin0 :ls weak and is so close to the 122l.~ kev line, its conter wns found by a S,?ec Lal p rocedure. Ti w b ackgi->ound countir1,~ rate was sub- tracted fr'.)m the re ,~ di.n 1~s tnus 1).vin.~·; tt1e lines on a level ( instead of' slo r ing) plot. ~ince ti10 1189 kev line sits on the tail of tbe 12211- kev line, the findin s of the center of t he line ( 01• its trt:t.e peak) is not as st raigh tfor...--;ard as in the case of a. line w·l1lch is sy.m:metricul about the center line. In this plot of the llo9 and l.22L~ kev lines the lo . .v energy ·tall of the 122l~ ltev line ts approximated by assuming the line is syrametrical. This tail i1as also been a pproximated • 60 by comparison wl th the 1.17 mev line of Co scale. [)lotted to samo 60 This standard line profile {1.1} mev line of co } matclies almost exactly the wnvelongth of t h is tantalum line and has the same v1idth. '.rhis to.11 ( which slo ;J cs under the lld'-) kov line) is then subtracted from the 11:}-;) kev line to g ive the tr•ue profile. The center of this true p1•oflle can be found in the usual way or by comparison with the 1.17 mev bO line of Co plotted to same scale. 'rl-1e gei 1::;er counter, described above, wl th the 0.005 inch thick co:op e r plates was used for' all these measurements . d It ls estimated t hat it gave 10 counts during all of the tantalw;1 runs. Because of the variety of wa.volcngtlw re ported ( see Tabled) in t he lower enor 0 y ro.nge it was decided to make a survey of the ~.hole wavel(mgth re g:ton in which l l nes had been re oort ud. This survey would never have been undertaken lf it h ad !1ot been that the automat:tc observin.0 me chn.nism h-:.1.d just been coup l0te d. The automatic obsorver (which as described above gi ves a printed record 01' t i:le counts) v:as set to take c::O minu te reading s every J . Ol.i. x-unl ts from 3v x-u.nits to d2 x-unl ts. This is 11.'.)0 setting s and too1r mL,.rly a month to 'I'hls of course co-u.ld never be attem p ted for a s&11 ;., le with r.:. sr10rt half life. This survey i;;O.Vc evidenc e of 6 lines in this ·.-mvelottgth r-eglon. a small scale. F'igu re 2l~ shows this su:r•vey plotted ·t;o A spectral interval requ.iriU[,; 1 00 hours of ::·ooot o pe r u tio.:1 to explore is uho,m. in the fi 2,ure. ,1eak0r lines than those r opm>t-Jd mo.y- of course exist but at least w0 can s ay that these six lines a.re the on ly ones which this spect i'orneter a ill resolve with ce.:r•tainty above tho baclrg roun.d with tho ;1 r<-:i.s0nt counting interval (20 minutes tel a set tin;:;) and the g iven s0urce strength. in As can be s c;en are no other places where tne counting rate i::.; l1.t 6 h on,)u L;h to C O.UtiB susp:tcion of a line. lwv lino i~ the weakest llnc, b0tnt; only l The 198 1/5 times the background c ounting rate. J.\ftcr t he vmvelcngths of the llnes were obtained fI•om thE} survey• 1 t was only necessary to make runs on each line {a det :.:::r rn.L1.atlon on botil sides of zero for ea.ch run) to detu:rmine t;he v:av0 leng t.hs of these six li nes. Table 6 6ives t h 0 results of measurements on those 6 l:lnG:Jo Six dotorr.1lnati ons each, were made on the 264, 198, and 152 kev lines and five deterrnlnattons on the others. !•'or each d0termination, the spectrometer re ,:1d 1.ngs wor•e cor- rected as descrlbed before {i.e. cor~ected for lev e l error, 1.:;o milltun3str0m f actor). Mo:.; t of the run;;;. were made using 20 minuto counting lntervals at each point. ;\s t he s ource decreased in streng th i t ,m s necessar:r to use 11.0 :minute i nterva ls . for t he weak er~ lines. The wei gh.t:tne,; factors in Tabl (~ S 5 and 6 were ass:t gned on the bas :L s of t ti.e number of counts recorded, .t n ot ner wo:r•d. ~ on the stati s tical errors lnvol1/.ed. Table 7 g ives a comp osite pictU!.~e of all 9 of the g a..11nua-ray lines f Pom tantalurn 182 wi"1lch have been determined to date. The± error g iven ie the probable error defined as 0. 6745 times ttle standard deviatlon. According to reference .22 t here are e:i.ght more d;amma-r~y lines of lovter energy, all of which aJ'e with in the re uch of t 11e spectro~aetcr. Because of their low enerz:s and the hl e;h density of tantalum, the absorpti on in the source is i'1 t 1)1 and t he depth in the source from whloh radiation will escap e ls very small (of the order or 0.07 nun. for the line). 74 kev For tllls reason a hi g h specific activity (millicurles per mllli 2;ram of mat e rial) is neces.'3H1"'J so trH.1t there will b e e nou6 h L1tens i ty comin::; from this thin layer to be de- tocted w:tth the sp ectromete r. The s p eciflc activity avail- able at Oak Ridge ls not sufflciontj A f actor of ten over that availabl e at Oak Ridge would be satisfactory and the cha ln 1~eactln,; plle at Chalk River, Canada would sup ply this b'_lt it is im·;) ossible at the present time (due to international rulinr1;s) to ha ve sarnples irradiated there. Thus the remain- der of t t1e t a ntalum s n ec t1..urn wi 11 have to be pos tponod untU.. a s am:)l e of suttuble activity co.n be obtained. - 13 - 4 'r ablo d comr}al"es ti1e reported valu(rn of the ener- .;ies of the g runma-ray lines from tantalurn182 • In ref ere nee al have essentially corrected their interpreta.tion of ·tlle electron lines as reported in reference ? 02 thi.c. r0ason t ~10 lines r0ported in roference l.acluded in Table o. 19. 11 arc not It is tc be noted that after r•elnter- :;::,r0tlni..; thelr· elec tro!1 spec t1'u.m Cork et al {reference 22) r0port onJ.J ti.wse llnos Nh:Lch our grunr;-:a-ray spect1"•omet01" detected. region. f l'cviously :mi:my mor>B lines wore reported in thls It tnus appears that tn tho lo w energi region t below 113 kev}, the llnes reported by Co1:--k ( and shown in Table 8) al"C prob,,.bly the only one/3 ·;;i1ich will be deteeted wi t. r1 tho g1.unrna-ray spectrometer. ,;,~·. R. 1fl 95 ( 1150) ( reference 22). 'l'ho t1~ansl tions indicated by dot; ted llnes arc;) those he al"ri ved at by a double inter• pretution of certain electr·on lines. r.rhe transitions marked \1ith a star (1:•) are :Jresumably the ones detected in t.his thesis. - l;.4 1. :~::y--1 :r,h Deter:.:. .tn~ti Jn of tile 113 lrnv Line Becuuse of the longer waVBlengths of t i10 other · r•o_portod lLw:s, the sensitivity of tho geiger counter is loH and extremely long runs would be necessar;r to de tee t tneso lines lf indeed they could be dctectocl ut a ll. How- ever, u:dn 2; 30 minute runs i ·t was possible to got a. profilG of tho 113 kov line on one ~ide of zero only. 'l1hls was done aftor all the runs had been completed and of cot.i.rse the souP ce had doc11Jed about ono half life. A line p.r•ofil8 was obtained with which :t t ·,uas possible to find the · center• of the li ne. By taking dlf'f'or>enc es of this lln0 position from t h e positions of t.!:10 6 other lines, a wavelength of 10-).27 x 10- 11 cm. ;,va.s arrived at. This gives an - e:rbre;y of 113.4 kev which is probably reliable to± 0.1 kev. Me asurerne ~ It ls to be noted thai; the seven lines reported above will determine uniquely all the levels given by Co .ck in Figure 2,5. It is nece:.Js ci.PJ to have the- 113 kev line to J.o t h is, and tile levels dot ur•mlned from this ;; ill not be as precise as tl-w others. Kno wl e dge of this 113 kev line is used in dctorrnL1ing only tht•ec levels ( the 113.4 level, the L:~0.6 level and ttl0 JL)-2..7 levol). ;,jinco the love 1::, iiave been deterrntned wi ti1 the 7 lines moasu.rod i G is !)OS si ble to ~) redict the other lines a 11 ttle more accurately if t.t1is level scheme is the correct one. It :.:-, ould, of' cour8e 1 be necessary to know the other linos as accurately as the ones already measured in order to check this level sche.-ne completely. FiguPe 26 shows this level scheme of Cork's, · r:10dified by the 6 lines known precisely and one line not so precisely (113 kev}. In the figm."'e, the values not de- terrnined, but only- infer•red from similar transii;ions obser>vod by Cork, are givc.m in parenthesis. It is thus very desirable to continue this work on tho 1:~rnama-i~ aJ spectrum of Tantalum182 when higher, specific activity- source stren t:~ths become available. 'fhe u.ctivi ty t ~1.at ,;o u ld be necessary can be deter•mined from tne following considei->atlons. 'rhe solid angle subtended by tho cry s t ~.tl is abou t J. x 10-5. The crystal gives about 5% r> ,:3flectlon at a wavelength of 165 x-uni ts. ( This was - :--:"; easu1,0d u s i ng trw l t3ad I<.:« c once.} i-0 - radiation excited. by fluoros- 1 The r op orted tantalum l Lne at, 75 kev (10.S x-u:aits) nas a mas:.; a b nor p tion ooe ff l ciont of 9.!.i. whic::1 is the hl k:';h- . ;~ st. of any of t11e re ported lint3s in this r 0 1 :;ion bec a use it is just on t i:1e uno rt wuv e len1-:ti1 side of t h e K critical absorption e cL~.e of t a ntalum. Th e .U.stanco in which the lnten- sL t j of this ra:llation ls reduced to 1/e of its value is 0.067 millimeters. If a samp le 0.2 nun. t nlc k a nd 30 m.,n. high is used ther·e w!.11 b ,3 6. 7 milligr ams do wn to th.is level •\7 { rv·'. ov r..rrn • ) • A countin;s rate of 5 counts per· minuto in this than ten times this value (i.e. not g re f\ t or than 50 counts/ ,~1 Ji.n.} wou ld be satisfactory. If Ne assur:1e the counte r has an effic1ency or 10;:i; ( po rho.ps a xenon fi.lled pro porti onal counter) and that the collimator tran:srnlte JO%, tho numbor of millicuries 1:iOt ivitJ in this l ine HOF ld n ~1 ed to be: 5 millicurles • 1 ar -l.i.~ ·,'.10 :::- ar t•1.cu L' \f '7 r;; 1/!..-ev ) • • • 05 To de to~nl ~e tho tot sl ecti vity e stimate wciuld be tha t of the: t;otnl ac t ivity. the tot o.l activity- wou l d be 10 iliLLlicu:t->ies this ,':[() \. l d C~l ll f o r a SlJC:)Cif ic 8.C t;l Vi ty th L s line 'l1h is ::ould l'nean i:1 nd in 6. 7 mg . of 1. 5 mill icurios . - !i.7 .. a fter l-1- months irradiation. Thus an irradie.ti ,)n of !i- months 'Nit, h a neu tron flux wh ich. 1.s at least 4 times ao great as . t imt at Oak Hid,se should be suff'ici.ont to determine these lower• energy l ine s. -48- ( l) ~r. t i • Jt1 r,ionJ., !t)~ fii .~£1 Re3olv-L~ f'o·:t Jer, ·ct11"ved-Gr·y stal .Focus.tn.5 S;Je ctrorneter for ~hor~ ,,avelength x~r•ays and j a1l '.:Ja - .d. f:ty s :i dc,v. ;Sci. I l.Q, 626 (1947) )-0.:.'..ond., Lind and Collon, 11 A,,·,Precision Nleti1od of Jenerat lng C i:r•cular CJllndrlcal 'surfaces of Larr;e Hadius of Gur>v:.1turo f'or Use in -tne Curved-Crystal .SpactPomotern Hev. .sci. I 1§., 617 ( 1947) Lind, ,Vest, and .DuMond; 11 X-Hay and GaiilITla-Ray Reflection :?ro i>o rtlos from ,$00 X-Unit;::; to i:Hne X-Units of Jn.. stressed and of Bent 1~artz Plates for Uso in the Two;;,.;.; ter Cul•ved-Cry s tal F'ocusln,,, Garmna-liay ~pectrmnetern Phys. Hev. l]_, i+7 5 ( 1950) I -. ( L~) #atson., Nest, Lind .~:nd DuMond, 11 Precision 6tudy of Pocusing Phys. Rev. 12., 505 ( 1949) 1::.. ·t i10 'Pun,_~;;:; ton K Spectrum Usinr; the 2-l</ioter GurveJ. Cr::rs tal Spi::Ctror:1eter 1' ( 5) Dufo.ond and Cohen, 11 Oµr Knowledge of thE) Atomic Constants F, i~, m, and i1 in 1)47, c.Elci of Other Constants .Del'.•ivable 'l' herefrorn" Hev. 11: od.. Phys. ~ , 82 (19/.1.8) (6) DuMond, Ltrnl and ,iatson, 11 Procislon Measurument of the .. 11veLJ;1t';th a:d .:;;,p~r.;t1,al Profile of the Annihilation Hadlation from cuOL~ wi t11 the Two-Meter Focusing Curved CrJ~tal 0Joctr•ornetex•! 1 rhys. Rev. 12., 1226 (1949) (7) Heitler, '1 ,,.,uantum Theory of Hadiatlon 11 Oxford Univer• slty Press. (d) W.A. Fowler, Not,Js from nuclear physics course (9) Covmn, (lOJ F. Metzger and Ni. Deutsch, ( 11) Owen, Moe and Gook, {12) Phys. Jev. 1!¼_, lbl15 (194d) '71, .Phys. Hev. i'h.ys. Hev. .J..l.k, / \ lt>q.O 1.Jd..:, 1879 (1-)l.J..O) Lind, 3rown, Klein, Muller, and Dul-fi9nd, uprecislon Measur .:nnents of Gamm.a-Rays .from rl3l wt th the 2-Meter Focusing Curved Crystal Spectrometertt 1$, 15/1-4. ( 1~149) (13) Permi, nNucloa1~ ihysics 11 University of Chicago Fress lurnstei n , ,<ur'O L-1 tov and Pool, ( 16) ::tall and i;.i.lkinson, .i hys. Phys. Rev. f'hys. Rev. Rev. §.i, >'3 {1943} ll, 321 ( 1}47) (1 -;)) Cori{ , Kel le r , ~)azynsKi , and Hutledge-, Phys. Hev. '1.S., 1778 (19\4) (20) C.H. Goddard and G. Sharp Cook, Phys. Rev. (1949) (21) Beach , Peacock and d ilkinson, Fhys. Hev. (1949) Go:eh: 11 1;~oll EH' .11 Hu tlectc;c; and ::, toddard , ,;5 (1 1.'.)v) 1.£, 1419 76, lSdS -50- TABLG l Range of Blectron.s ( Ml lllmeterf3J 1 I . Range of gamma-ray secondaries in Al . Hunse of g a,'nl!la- i-·ay secondaries in cu • • 042 .05 .016 .25 .08 .10 .03 0.3 .35 .11 .16 .05 .q. • ::,!) r 'r' .17 .25 .08 n ,,, V O.? .72 . 23 r' . 3:;; .11 o.6 . 90 . 29 .45 .1L~ 0.7 1 . 08 .3.5 .58 .16 o.8 1.27 .lµ .70 . 22 0.9 1.~1.5 . 1~6 . d,5 1.0 1. 65 .52 . .27 ,, ')8 .31 1 • .5 2. 65 .as 1.75 . s6 2 .0 ., 70. J• 1.17 2 . 60 .83 3.0 5.90 1. 89 !-l- . L1.o 1.41 i•~f:V RAl 0.1 .13 0 .2 0 Rou -51- GOLD 198 ftESULTS Colu.,•11n A Date Hun Number l June 19Lt-9 Corrected screw divisions 30.096 d 1 30.101 1 30.076 30.063 2 1950 3 Column C Column .i3 divided in~o 12395xl0_: 1.00029 Axlo- 11 cm. Energy in mev 30.155 30.150 30.162 30.1 6 l-1-11.043 Lµ.1.111 30.118 30.112 • ,Jan. }..0020,l 30.101 2, 0 Column B Column A multiplied by 30.155 410.811 410.B93 Lµ.1.043 30 .128 l.i.11.L1-11 J9.068 30.115 1+11.598 J0.120 lJ.ll.!z20 30.092 ± 0.007 30.145 -:r. 0.007 l_i-11.178 :t;: Q. 1 The± error is tho probable error +0.001 +u.001 +u.JOl -u.uOl -0.001 -o.ou1 -v.OUl t7.940 b7o9f1 67.950 '7 • 9······· o· j j. 2 3 4 5 +0.018 -0.006 + 0.001 + 0.003 +0.002 -0.002 308.705 EY7.u90 '.;j l 87.091 l ½ l 308.798 + 0.010 2 3o8. 78t, l 3o8.797 l + 0.008 l l :3u8.785 +0.002 + 0.002 308.785 +0.002 +0.001 b7.937 07.960 l l l wt. + 0.004 - + u.OlJ 07 .. 942 + u.002 + 0.006 b7•92:/ b7.964 reading COl"':rec'ted + 0.014 Level +u.001 + (.).001 -0.001 u7.950 ?e1•iodic l . /,,No.• screw Correct.ions 87.091 308.795 67.946 Average 43.535 154.3o2 330965 (siegbahn) x.u. 284.13 :t 0.1 43.622 ±0.005 80.133 :to.02 154.071 ± 0.01 . 364 .. 18 ±0.1 34-0'33 1;nergy • kev :f.:0.01. ~g in io-11 cm .Errors in the screw and in the Carriage Mechanism of the Instrument .Reading .hilll J Reaul ts of .Independent .Me[; sure.nents on Iodine 131 Before and After Corrections for Small TABD~ I I I\.) v, -53- iifa~lengt~ 11easur~ments of Tw.Q....9a.mrn~-Hay Lines From Co60 1.3 Mev line 1.1 Mev line ._ . ,_ Screw Screw Reading Je i gl1.t (Double) Factor Hun l 18.570 0.5 rtun o 21.111 Run 2 1a.595 1.0 Run 7 21.118 Run 3 10 • .573 0.5 Run 8 21.121 Eun 4 18.555 l~O ., :,Un 5 l d.573 ,Wer. 18.562 __ Head ing; ( Double) l --., ,I Averag e 21.117 1.0 9.0 . rrec •. {<10 • .578±0.005) .: ·:e sults 11 10C?ilS 1171.8 Kev :t 1.0 Huns 2 ,lk, ~ { ' 10 . $83 Corr0cted Results X ±o.•005) x 10-11 ems 1171 • .3 Kew ± 1.0 . A,v erago 11 6 , 7 ,B Nelght ,~ ,.. ~o,-58~ ±o.005) x10ems 2 , L~ ,5 ;V e:t ght 0 • .:.,l1171.~ ri.ev 1.0 ! ± -54- Hun No. ,~a.velengf£° 0111 X 2 Average: 10.121 1 2 2 10.14-32 10.l-1-J' 10.4-1i 2 Average: 10.iH:8 10.425 l 2 2 11.060 11.035 11.0b) 2 11... 069 1123 • z!.~ { 1 056 ± 010 1129.1~0 l • . • • • • X 10-ll,,.m 1112_.79 1121.1 ± 1.0 kev Average: 11.056 1121.08 2 3 11. 1 2 l 10 10.127 10.123 10.121 10.118 l 2 .1 2 KEV 1120.70 V ±Error gives probable error -55Data 0 :1 Si x Ta Run No. Wei ght l 3 l 2 2 7 2 2 .5 2 8 2 l d2 • Lines Ave r age: 1 2 3 5 8 l 2 3 2 2 Average: l 2 3 5 5 221.937 l 2 2 2 1 222.053 Averaae: l 2 2 2 3 3 3 5 b 8 62.526 62.516 62.506 62. r.·20 2 2 ti.verage: l 2 3 5:, 0 1 2 3 I LL 5 8 69.odo 6-9 .11f-' 69.112 Average: 81.331. d1.30~ 1 2 2 2 2 2 61.326 51.303 61.306 §hl20 Average: 9 l 62.483 62.518 62.512 69.114 1 2 3 l -± 0.011 x 10- 11 cm 222.10 t5S__._ •820 222.061 .. 2d2.0l3 2~2.053 222.1,36 B1.31l~ 109.27 ± E1•ror g ives p robable ei-•ror ± 0.011- .lteV 1 -56TABLE 7 ~el.£1..~hs _fill,4_ ~9.uantum, E11e ri3ies of Ta18 2 Gamnui•Rf.';,;l Llpes ·'3 Decay, Half Life 120 Da.'.(s iio. of runs avo!•aged L~ 10.121 ± 0.002 X 10-ll 4 4 10e425 ±.0,006 X 10-ll ± 0.3 i1J9.o ± o.6 11.0.56 ± 0.010 x 10-ll 1121.1 ±1.0 1224.6 He g i on from 1121 to 3/.~5 lfav not yet exp lo1.. ed. Reg ion from J!;.5 to 263. 9 J<,:ev explored w1. thout reve a ling any clea r-cut eviden co of line s . . 6 46.91+6 ± o·.ooa x 10-ll 26}-1-.026 -±. 0.05 5 Sl+.063 ±. o.ood X 1o•ll 229.270 ± 0.035 5 55.520 ± 0.011 x lO'"'ll 222.053 ± 0.04 6 62 • .512 ± 0.010 10-ll 198.202 ± 0.035 5 69.10.5 ± 0.010 x 10-ll 179.365 ± 0.03 6 81.31L~ ± 0.008 x 10-ll 1.52.h.3!~ ±. 0. 014 1. :,:: 109.27 X :t 0.08 . x 10-ll 113 .}.~ ±error g ives prob a ble error ±0.l -57TABLE 8 (All valuos UI'O in l{eV) :Jal'.!U,ia--ra.y s p 0c tror1etc:r values ( ;)resent) U-odda.rd ar1d Cook P.R. 12_ 11~19 ( 194.1 ) • Beach, I>eacock Cork, Koller, .and .iilkinson Rutledge and Stoddard P.H. 1.£ 95 (1950} J.!2. 1585 (1949i P .R. - ------+--------+--·-------+--------112J..l 123~- 1237 1190 1219 1120 1133 32!,. 26i+.O26 261 264 ' 255 2l~3 220 222 221.1 198.2d2 209 198 170.365 180 172 197.5 11s.4 165 157 151.5 141 (143.2) 132 (lJJ.8) 122 113.4 112 113.2 103 98 99 8~. 82 71 74.a 67.2 6.5.3 sa.4 J+6.o I FOCAL CIRCLE 2 METER DIAMETER - YSTAL B COLLIMATOR GEIGER COUNTER A s ·•R p 1·1c.ru :r~, 1 J. C SCHEMATIC DIAGRAM OF SPECTROMETER Q:) \Jl. - 59 \ \ \ \ \ \ \ I I I I I I I I I I I I I I .~. ~;- ,;-;. I I '1 '1 ,. ,..:.l \..1 •·1 • I { ~ ... -~ :.- ! '• ,., ::. .. , :.. ~ ... ~ ,... r! 4 -~ .~) -.:.."! .). ) /1 -~ -1.~ ·.:: X\ ,., ~:.) .C! (; -;j , .,t ;...> •. , C) 0::: -, -t "" -..:J ,v :·r; . .._! -;;; - ;} ~ ) "< \ ;,;_) .,1 ·< c:1 ,; l .i,) \. ., '.J '·, , f \ t ; . ..1., q"j \ \ -r: .;.t \ \ \ '] ) \ .:1 :.~ :....... ·.;; '."I J.!' :·< ~;, ~ .1) ,··-'i • ·" .. :.. -· ''( '.I ... ,c • 4 ";;~ '. ) cl ') \ \ \ S.:·) '.::i :r~ ,) \ ·, :l \ 1) 0 ·~ J \ I I I I I I I I I I I I I I II l1 l1 > •• ◄ I I l -.. : :,) '.'>} "' ·~ -~"It • .- -i Ii} • -\ - 60 - c, ,,,----s / ....... / ' /~,1 8 ----/4/: e I II I I I ., I I I I I I I \ I I I I I I I I I I I I \ I ' II I I I I I I \ I .r'iE,-u.1·e _::;. :fvc'.i.;Jir,i~ I I I I I I I ; ::u ru1icamcn t i11 2·0::,me tr/ ::ipect1·0Li°'1e t t: r lamL.:;6 is hm t circle , I I I I ~ ) I l I \ U!:>E!J. ') f \ I I ./ I I I \ / / . the c·..i.r-ve c: -•cTystal in tnrn~x.,i.l:lsiort is st -:-wn . 'l'he cry::ikil t c, u :nd lu a e :1uel to t.ri.e d i ameter of tbt:, 1' c:i ca1 ~ raf re ~~nt~ t he so~rce pouitlon; Ci the inte raection ,::, r Lb.c at ,.,m..i.c ;,l h1:. es :,.o tne f-:, r::n.l c:L:·c:.1.e arid l ttw vi r tual sour ce ol' tLe .n:1diati :,a olt<:'r c. U 'f.'ri; ;' ti -'.)ti ty the la t tic~. '!.b: r.e u t::·al ·J r t ~le ben ~- cr·yst!~. l i s tGni t; nt tv t :": e f 0 cJ::li c i:· c'l.f: e.t C~·• This geurue t ry i ~.t ~ t t; t.; ;J ,:i Lt 8~..-: ·t :': •:; n t:: _j _7,,:t,~--l i b .Jul ,1 c ~ ln ._ ; i de -t i.A i ~; L ~ ; -~ ·.-:: ) ~ ,'. -~ t1A E · .' ; - 61 / NEUTRAL AXIS Of f BENT CRYSTAL __.===-~--===~- I I \ I I I I I I I I I I I I I I \ 6.9 ABERRATION Fie:;\.U"e ~\. Gcomet :·y dete ::'!nining tte Line l:rroa.dening or aberration in t:.te trar1;;rn.1s s ion-type spe c trome·ter which results from the fact. that nce.r 1 t8 ex tre.mi ties the neu tre.l axis of t he .lruuina fails to coincide with th~ roce.l ci.r-cle. The abf::1rration68re 13 u.lts in a corresponding waveleng th aberre.ti0n A~. :Fo r a.m all 8 e,uJ ct, this eberrs.tion is ex t .ri:::mely small . - 62 - SOURCE SHIELD LEAD FRONT VIEW SIDE SECTION Figure 5 SOURCE HOLDER ' 0.50 """0.4 0 •I I -e- -e.,.,,.._ .,., LEAD 0 (\J --e+ .- w -e- (\J ci _ _ _'L_ w co .,., ,., .,., _ y_ _ LEAD ~ ..l'..... .J... . l ~----------------R:. _____ JI SOURCE CLAMP SOURCE Figure 6 - 64 COLLIMATOR REAR V IEW SHADED SECTIONS ARE MADE OF LEAD STEEL FRONT VIEW Figure 7 65 - 66 Figure 8 CRYSTAL HOLDER I '\ I I I I I I I I I I . \ I I I I I I I I ,.L~ I I I I I I I I I I I I " I I \ \ co I I " • er e.r ( ( FRONT VIEW I I I I I I I \ ~• I I I I I • er:. I I : I 'I I I I I .. I I I I I I I I 2.0 0 I : I \, r 7 ,,, i I I \ \ I I \ , - L, I I \ I I I I I I I \ \ I. I I I 0 0 - 67 - QUARTZ CRYSTAL (UNBENT) 7 A d /(310) PLANES OPTICAL AXIS Figure 9. The (310) lattice planes of Quartz lie so that they are parallel to the edge of the crystal and normal to the major faces. The crystal is bent elastically so that the optic axis, and therefore the (310) planes, lie parallel to the generators of a rig~ circular cylinder. - 68 Figure 10 0,5 1.0 0 1.0 0.5 OPTICAL MM FOCUS 3 ,..ec '2, \ ' '<;> v \ \ \\ \ C, ~ l>- \ '' \ t- Aa 4 I I \\ \ C' C' I / / ~ 4 / I / / x.u . I \ \ \ / 2 MM 6' I \ \ \ \ ';<9 I I I \ s $-<J C .35 . 20 t \ A 2 5 6 B X RAY BEST FOCUS WIDTH 0.07 X.U. C CRYSTAL APERTURE 0 0 Q 0 0 0 0 11 '1 '1 ,: f.--3.875SQ ... , ;, '1 11 :: ii 11 ~~---::~~~~~---:~~==~~) I ,1 I I: :: 0 I• ,, :1 11 II 0 11 11 ': 11 11 II II ,, r l- ------ -- --------tl ~3.22 so +-4 t-- 1.so SQ ....I + -~ COPPER PLATE i== 3.22 SQ .. , ~ ~0.25 CASE Figure 11 COUNTER - - - 8.75 - - - - - - - - - - - - - - + , ] --------- - --------------------- ~ - - - - - - -- _________ N ~ ~ ' ~ ~ , , --, \ 'QI ',_ , ,_ (--~--,I ,., ~ro.012 ,,,, @ '--✓ (~'~ ..... - ✓ (;--~ I ,, Ii :, 'o '1 II II 1 !P " ,, ----=---- -----\\,, WINDOW lL=:_-_--------------- --- ', 3.25 SQ LEAD GASKET ,.._ ALUMINUM ---------,------- ------- ------ -----~-----~, ~---l~o.oos PLATED) SPACER (SILVER '° O' 70 0 0 ~ w > 1- z 0 a: i... 0 (/) a: w 1- z ::::> 0 u w u z w a u z 0 u 1- z < ~ w > w a (/) ·r..ER -:- _..) ; I : ( . R-1 R-2 R-3 R-4 R-5 R··6 R-7 R-· 8 R-9 R-1O R-1 l C C~l:1.~,, r · R i'--7 ··c: L I --.::! _ IW 5 MEG IW 5 MEG 10 K 2W 50 K 150 K IW !OW 20 K IW 200 K IW 150 K IW 200K IW 200 K 50 K POT - ~ 1 0 Figure 13 C-1 ~002 M FD 2500 V C-2 001 MFD MICA 500 V C-3 100 MMFD 500 V ALL TUBES ARE 6J6 6.3 V. TO ALL FIL. CIRCUIT R-· 11 QUENCH OUTPUT LO-CAP. CABLE -105 V +2ao v H.V. t,-J -.J ?, 2 -=- IC9 4 mrnmrn 6SN7 Figure 13 A ~tTZ~] 6SH7 tJ 5 9 G 7 8 1 . l ~,i,... "f C 12 ~ r C 10 'J " C C C 4 _,,'.l 2 j_ R9 .~ ,..,,__, ;.,. "'' ,, (' r·• Cme uIT ,,2 -=~ TI RIS T 2 Al':T 1~-: QINCJ,DLI-K:E_ 4 BANKS OF ANT!COINCIDENCE COUNTERS ;,, CCl t J'D ~CX11 100 100 tlhlFD .CX)l :;~ "° 1Jl ~FD 1 .bel :,_;-·L ,. 001 1~FD ., C:Z)l hYD . {X)l f.~~ D . 001 :..r:, .001 1.t1.-1J t,001 1~.FC 22 K 75 K 500 K R. 12. . ' 1 ., .J...) 500 K 200 K 7 "5 tiEG .l r.EG R 16 R. 17 F.. 18 R 19 50 !< H 15 R. 14 !~ '"'; " ..i..J. 2 t\.:-.::G 4 i~;.eG r ') B. 10 l\ 1. ;'i;:~ G 2 li~:G ? h..:2G ;! :¥. EC; QJ p. , rr. :l 5 ."2 i\1E.G ? K 6 7 S t~~;:c- P(!T ~ := ,:..r:G ?CT 3 1 PC:T :.ii:rr .r,. ~i . .!.:~~ }.·• : ~ -~ ·; •1 :~ R R R ALL FIL. 6,3 V. TO +2 80 v. H.V. I\) -J FROM C0INODENCE CIRCUIT ~ ~ Figure 14 ANTI-COINCIDENCE CIRCUIT 20 K ~· IOOK! .oos ,ISO K FROM ANT I-COINCIDENCE QUENCH 2 MICROSECOND 10 SECTION LINE 280 V ..--t-:::: .01 MICA ii~ TO SCALER v-) -J - 74 Figure 15 TUNGSTEN K CX. 1 X-RAY LINE 1760 1600 • 1440 Z ~ 0:: w 1280 o.. 1/) t- 1120 z f u \ 5 r w 9 60 I- < 0:: W 10TH (.:) 800 2 1- z ::) 0 640 U 480 SPECTROMETER SETTING . . a,.. . r-,.. CO 0 (5) 0 C\J - C\J 0.250 X.U. - 75 - 1--- - - -- - -- --·- ---·---···---·- -- ---- ·-- ....... j,• . Q + - --· 0 rt) I t - -- - · · ··- - ---·- I -l, -- ----- ------- ·-------•- · ----! z ' I X z co I S:3.1-nNI~ S' Nl SlNnO:::> 0) _J f:::, ··-'--· 7 - · · · - 0 Cl) 0 0 (\J rt) 0 tC) 0 0 z 0 ~ w _J w (0 C\J 0 > t9 ; ---- ... ------- ·- .+ i' ...... I[) ,_ ·-· -· ---- ·----- - •• 0 • rt) ~ ~ '° ;; ,-f Q) ~ ,rt f:q 0 d rt) - 77 - KEV 3 64 131 80 KEV ZM KEV 638 OWEN 531131 MOE AND s,4Xe131 163 KEV KEV 284 FIGU.HE 19. Disintegraiion schemes of I 131 DEUTSCH s4Xe I 1274 I I I I METZGER AND 531131 COOK 80 KEV 364 KEV 0) -J 79 Fi 0 ure2O,Three spectral curves showing the 1.1 and l.3Mev lines from Co'tO as reflected from both sides of the planes of the curved crystal. Run I (n ot shown) was exploratory, to locate the 1.3 Mev line. RWl 2 shows the l .3 Mev line while runs 4 and 5 show both 1.1 and 1.3 Mev lines. The source was removed from its holder after run 2 to permit temporary study of another muc_h shorter-lived source which had just been received, Ta182, The Cob0 source was then replaced in the instrWTient and another exploratory run (rWl 3, not shown) was made to relocate the lines. This removal and replacement of the source accoW1ts for the slight shift in the wavelength position of the lines on the instrument scale, a shift corresponding to a displacement of the source in its holder of about 0.07 mm. The separation however between the respective reflections from the t wo sides of the crystal planes (which is u se d as the measure of the wavelength) is very reproducible from rWl to rWl. Scales at the top show the Bragg an g le in minutes of arc and displacements of the screw carriage L (relative to Q) in millimeters. The wavelength scales shown are in .,nominal n1illiangstroms. Their differences are converted to true milliangstroms (lQ-11 cm) by multiplying b y 1.00179, the factor determined by the X-ray calibration. More than three times the total width of this figure is omitted from the wavelength scale in the space at the counter. The ordinate scales· are indicated by nWTibers giving the total nWTiber of'counts accumulated at each setting in a 1,000 sec time interval. - 19 - 80 - Figure2l. T h ree more runs taken on the Co60 1.1 Mev line alone. Here the source was not disturbed and this gives a go od idea of the reproducibilit y of th e mea s urements, when the in s trum e nt i s at it s be s t. The scales on this figure are s irn ilar in all re spec ts t o t hose of Fi g ure S. - 20 - • 2240 ~2080 1760 s~ \ t \ \ I ~ --I I .~o .40 60 .6 o .so II y1 \ 20 .40 ~2720 -,2880 -12240 I -12400 8::> -,1920 Z ~ .:-12080 ~ u ~~ i en Z --12560 O ~ ! · ---- - I- _ -- -,o.oo . I .so I I I\I I I \ II ,, 1.171 MEV I --r11JL __ . LI NE SPECTROMETER SETTING I I GAMMA RAY Figure 22 1280,J _______ - - 1440 I t/ _JI I l I /, Y II \ 9988.80 89.00 u 0 i t, 2 1600 ~L ~ 1920 <ll Z I ~ z I Co '" ~ - 82 - U) 5000 w f:::, 3000 z ~ ~ ~ U) f- z 4000 :::, 0 u 2000 16 x.u. OMITTED X-UNITS I -11.50 -1 1.00 -10 .50 - 10.00 9.50 OBSERVATIONS TAKEN EVERY 0 .04 X. U. ! -! -- I ' ! i I I i 2500 'Z. 1---+"1--+--, :i :i ~~h ~+--1 · 1 ! 0 N 0 z z 0z •♦ -- ' 2000 I -69.5-69.0-68.5 x.u. x.u. . x.u . u f1 I . pi)\~ I . • 1500 I x .u ! I II I i I I i I -47,5-47.0-46.5 x.u, • i ! -54.5-54,0-53,5 -56,5 -56,0 -55.5 z 46,0 46.5 47.0 x.u. • -'-1· I • • ! ' ;J(L_ ~ i :, 0 u -82 .0 -81.5-81.0 i N :, 0 i I I ! / II i i 53.5 54.0 54,5 x.u. 55.0 55.5 58,0 x.u. 61.5 6 . 82.5 XJJ. 68.5 69.0 69.5 X.lJ. --.__ OBSERVAT IONS TAKEN EVERY 0 .04 X.U,___.,,.,,.- GAMMA RAY SPECTRUM OF TANTALUM 182 i I ·---- ' -~,9_0_ ~7 -_8_0_ _ _-_1_0_ _.__-_6_0_ _ _-~5_o_ _ _-~4_0_ _ _ -3_0_ _ _-~2_0_,.....~c.,-~1TToTTTTrr_ _o_ _"-rnlITTTT1no~ l~-2~0--,---3~0--'--_4_0~-r'---r-5_0..--"--r-6_0-r-.-,7-0-r_-,--8_0--,.--~9~0 1,4 ' ,.- ,.'6 1. 7 1.8 1.9 I •10 • E .V. 2.0 I 3 .0 I 4. 0 ~<'.o T 6 TT I! !llpil lJ 71 8 9 1 M.E .V 2 M.E.V. Figure 23 1111111111 1 2 M.E.V. r } 1 M.EY. 5.0 4 .0 3 .0XlO'E .V. 2 .0 1.9 1.8 1. 7 1.6 ,15 1~4 83 - 85 E XCl1'E D 5 TATE OF TA 182 ~f 73 ENERGY LEVELS 74wl82 _,.......,._ _ _ _ _..,_ _ _ _ _ _ _ _ _ _ _,...._ _ 441.0 KEV 99.8 _...,_...,._ _ _ _ _ _ _ _ _ _ _...,._ _ _ _ _ _ _ _ _ 3 41.2 221.1 * 143,2 I 2 41.6 I 262 . 3 I I 228* .,I I 'f I 9 7.5 I I I I I 76.8 I 58 ~4 I I 84.4 I " ' 17 8,4 I 1 151.5~ l I I 65~3 l I I I 133 . 8 1 120.2 , I 74.8 113,2 6 7.2 I 113.2i 46.0 0 i 'IGUiili 25. Exoi te d levels (kev) in w 182 following beta-emission from Ta 182 according to cork,Keller, Ru-Uedge, and Stoddard. (s ee reference 22 ) - 86 - EXCI'f!ID STATE OF 73Tal82 ENiRGY L&VEI.S IN 74 wl82 443.39 - I I r-- • I § I --. ► :} !"'I 0 ' ~ I r-N • T I I 342.7 "';'1 ,_., ~ I s ► :A I !t ~ I ◄I • I •I "'• 0 ~I ;¾t r3 ij .......... ,-1 'f 'f I ...-;- 1 198.28 T I I I I ,;;~ "'• «1 '--1 . .~ . - ~ :! (0 Q • (0• N N ~ ...."', I ~ 214 I I ~ I 0 t-- I •I ~ . to co• 0 I~ 1- ~- 120.6 I . ~I ~ -~ I 214 I '°• ~I ~I ~ E{ <"'\ ,-t 1 ,....► Q) ► 214 :A -►' U) ..,t '° 113.4 ~ r::• E• ~r--• , ...::.-. ~ co .' '. ,, • ~ FIGURE 26. Excited levels (kev) in W182 following beta-e11ission from Ta 182. Revision of level scheme of Cork et al on the basis of present measurements., 0