Kimura, Kiichi

Uemura, Yoshiaki

English

Kyoto University Research Information Repository

RIGHT:URL:CITATION:AUTHOR(S):ISSUE DATE:TITLE:A Counting Instrument with LinearAmplifierKimura, Kiichi; Uemura, YoshiakiKimura, Kiichi ...[et al]. A Counting Instrument with Linear Amplifier. Memoirs of theCollege of Science, Kyoto Imperial University. Series A 1940, 23(1): 1-61940-01-31http://hdl.handle.net/2433/257240    A Counting Instrument with Linear Amplifier                                         '             By Kiichi Kimura and Yoshiaki Uemura                      (1'Neceived, October 28, Ig3{))    li<ecent development of nuclear physics has demtLncled tlie develop-nl{,i,llt oÅí a 11exv 111clasLlrin.cr illstlrulnellt. tX counter xvith linear eunplifiel"was originally constructed by C-xx- einE cl}c)rt) aRd then improved by NVyni)-XVillianis ancl WardsL). Thereafter, several designs3) were reported ofamplifiers simila]r in pxinciple to this one. In our labor.'ttory too, theinstrument was constrttcted with some improve.ments Åíavotu'a' ble to thestudy of nuclear transniutatlons4). Since, by ca't`eÅíul constr"ction andproper adjustmenir, the natural backgrouncl oÅí tlie cotmt of this instiru-ment ls obsexved to be.always less than one or two per hour in thecase of the small ionization chamber described below, it is founcl to bemost convenient for measuring the protoR and alpha rays not onlyfi'om strong' sources but also froin very weal< ones, since evcm s of the•particles per hour per cm2 of the surface of an emitter may be ascerta;.ned.            • Fig.iili$l#.' ,617l tea"r;afit•tva..t la:estttttt"e2,"tt2ag'z.s•Apt6e",Ebo#{tle. 2ny'e`.ott•ff•ee4X:t-tt4''252eoe dew'-/s.. za. ..vax.vacrtV'ndpt""op •.i•/n..fi..ttAM'.'I.•.•,,1,?- ,rwff.••.... M...x' .k'./•".ltatgt.as.-.X l "l•t• .'- g-..'ast•••e EYY.-tt tttt,tt.•hi tt.///tttt',/l,////i+2eeV'-+boeVJ +6 y. i- 2tyV. +2tsY. O v,2 Kiichi Kimura and Yoshiaki Uemura    As the genera1 de$cription of an amplifiei' of thiS type js givenby the writers cite,d abovei':"") it is only necessary here to describe thaparts improved by the presei3t xijerkers. ' 'a) Ionization Chamber    'Jrhe countint.,' chamb{-}.r, "sed (I?ig. D is a pairallel piate condenseirhavlng a collecting ele.ctrode 'L, cm. in diamcter. The inner electrode.i$ surrounCled at a distance of iinm. b]yr a circular guar.cl rlng. The'clepth of the ionization chamber is made adjustable by screw betweeniomm. and 2inm. (from the inner collecting e.lectrode.) and it has acircu]ar opening .7. cm. in clianieter coverecl by a thin sheet of alumi-nium or mica. "1'he exterior of the outer electrocle is shielcleC{ by an(ittrthen cap with circu]ar opening, which defines tlie effectir)g area ofthe $ouTce to be studied. This shielding is found to be indispen$ablefolr accurate lneasllrelnc)nt.b) IJ.inear Aipplifiou:    The. Iinear amplifier constructecl by us ls .i fonn of resistance.-capacity coupling. I{aving beei} used in several experiments5) for longyeairs, the. kmctlon of this amplifier was sttccessively iinproved so thatit js used qttite satisfactofily ln the high voltage and crowded rese4rchlaboratory. TliLe circuit diagram js shown in Ng. i ai}d 2 and theva]ues of various components are incllcatc--.d on the accompanyi.n. g l<e.y.i) .7.7id.fr'trsX .s'X(r•.(rv q/I !.lie amPli7er As the mos.t critical point of the           tt          •, . I-"ig'.2 '              '  .• 6J7 6J7 6J7 6JY 6F6rlliint"W---'-5lil'+6-tvaTHfi,(.l}-tenvLfiff-vIii+bl-rrgA•LE1gar1+2eot'"BooY-C•le 2J `.1s]'xT o, le -•, 2oR,,2j" le 2, #i;1, 2, ''' fiC,1    '2tsv,   o oos y,ll;,   2ul,   ioo,coo9.,     2,ooog.>,       6(:),ew- rogst,+21ev•G2C"'r3, o nkTl/sr.e, 3, 4g.,I)l) 2    tJeeV• 2so,ooog), 5oo,oooO,•I,ooo,ooo(-l-,- •2o,ooo9.,  5o,ooo[)•,  so,ooog),  +)eo" pteeV•1),?,, --2so,oooS),I), 7,ocx)ge.,Yl, 2, .•,4 s,oooQ.,]1't, 2,ooOO.,Sv 2, •.,4 50,oOoO.,S4" -- 2,oOOL'->.            A Counting lnstrument with Linear Amplzfier 3amplifier cornes in tlie first stage, the present workers, as have Etlsoall the others, have carefully laboured for this point. The valve oÅíIIi<C.A-6J7 or UZ-77 (Tokyo Electric Company) was found to worksatisfactorily (I-"ig. i). This has, to a certain extent, desirable chairac-teristics, i'. e., low input capacitance, hi.crh ainplification factor and non-microphonic construction. Because of it$ high noise level a valve ofthis type was considered by some• workefs unsuitable for the first val.ve,but this difflctdty was ov'er,come satisfactor.ily by proper conterol 2n theway descr.ibed below.    After several tests it was found that the sistnal-to-noise•' r.atio wasapproximately independent of the plate voltage over ca wide ope.ratin.g/"arige, bue was closely depenclent, on tbe plate current as affected bycontrol of screen grid voltage. The noise level conid be greatly re.ducedby operating the valve at low• er cathode temperat"re and with ]ower.screen .orid and plate voltage ; for instance, tt good condition was ob-tained by using a heating current of about o.o8 ampL'rs, a plate potential                                'oÅí 2g"•--48 volts and a screen potential moderately controlled between                   'i2 ancl 24 volts. '    In order to l<eep the amplifier always free t'rom temporal impotencecatised by sonm large eiectric disturbances and to gain hig'h resolutlonof counting' enortnous numbat'$ of particles i,n a short time withoutg/reat sacrifice of. sensibillty, it is found clesirable to use a g'rid leakresis.tance, at the first valve, of the order otE io" ohnis "•rith the gr.iclvoltage oÅí about-o.8 volts whi.ch is the. value of a floating g'rid. Noi-emarkable increase of noise ]evel was observed in this cttse as com-                                                                ttpared to the. case. of floating g'rid. // '                                                            '                                               /ii) S'rki'eld t`a•se The. shie.]d box of the .'•unplifier "ras at fir$t niade fronRbra$s plate 3mm. tliick. But the brass plate of this thicl<nes.s wttsfound to resonate with so".ind waves 1'rom a neighbottring- wo}king'machine and especially from a loud speaker connected parallel to there,cording" .system itself; and so boxes of iron plate i cin. thick xv{,iresubstituted. The naere change oÅí matexial wa$ found very effectivefor obtaining goocl stability in the •fimction of the amplifing systeni.    IEach stag'e oÅí the amplifier is mounted on a separate hron casewhich consists of three compartments ; one for the valve, one for thefilter circuit and one Åíor. the coupl'ing circuit. To l<eep the valve frommicrophoiiic effect each vaive has bc.'en suspende.d by soft springs withrubbc",r sheet, and the connections xvere niade entirely froin flexible•(dead beat) wires. In ordei' to absorb mechanlcal vibiration through the4 Kiichi Kimura and Yoshiaki Uemuratable these i't'oR boxe$ have been mounted on piles bf wooden plette.sseparated by pillars of sponge gum. 'jli) Co72t•rol of a.ptiPliJiZdati'o7z thkXs a slight changc} of tlie. screen grtclpotentjal of the firs.t valve has rernai'kabi.e. infiuence oii the. outp. ut of                                                                 .               Iig. r, ,• ' the ainplifier, the contro! of                        ' .aniplification has beeri e.ffect-          l          : e.d in this way without dis-                                       turbing Åíhe lii{eation. Thi$                                       may be also possible at the                                       secon.cl stage. 1t i$ desirable                               g- nv to control both complementa-                               i'1/[tn.gi.i/s,ryx,i2e.k':>l,;`;•as//e,,eifi:                              .th."t•""'i- ' • the lineatioR. N7gTitla otheir-                                   '                          . t mo''ij"" fi;' inethods, pub12shed pi'evious-'                             ''' ' 'ly by severa! worke.rs, th;,s                                       ope.ration also may be a con-                                       ven{ent inethod.                                       c) .I;l.ecording' Apparatus                                           A sitnple osclllos,rapl)                                       i'econsts-ucted Åírom a bal-                                       ancecl- armature-loud•-spertker' '          , has been used. (Thls is pre-          i          i • ' ferable for observing the                                       "1<icks" since 2t recorcts                                       parallel to hearing.) A natu-                                       d.tl freqtte.ncy of about iooo/                                       sec may be obtainecl without                                       difficulty. The construction                                       was inade folloxving', in some                                       respect$, after XVynn-Wil-          iM . ]iains'"'). (Fig• r))     'JLhe soft iron arma,ture A is a shallow rhomb in shape, the diag'oiTials of which are Jsmm. ancl 8iTnm. respectively. The vertices of tlie• longer diagonal are suspendecl at the center of the speal<er coil by two tiingsten xvlres 8opt in diameter forinlng sides of a loop which i.s stretched by means of a screw-and-pulley dt-tvice. The distance betxveen the two briclges of c•bonke is i.2 'cm. IFor current coil, ac s.peaker coil of 2ooo ohms (,lectrostatic i"esistance is $atisÅíactory.I-ovzcm,-H--l---ttt..M-.-t-t-u.ndt-rvt '.----iiIA.t m-..ttt.. .t-t+tN..' g-.xi,eN'.s5-' ttt.. ne-.t.t            A Counting ltstrument with Lin'ear Amplz:fier s    A thin .o'alvanometer mirror M about s mm. sqttare is attached tothe armature. This whole part is immerseCt in liquid parafllin whichacts as a damper. 'rhe optical systein is moimted as usua!.    Camera-A rotat2ng paper (or film) came.ra was specially con-structed so that a strip of hi.o-hly sensitive bromicle paper or photo-graphic film stretched arouncl a wheel {s clriven smoothly cftt variousspeeds by means of a phonomotor--anct-pulley systetn. (Fis,. 4)    The sensltivity of the oscillograpb as i'isually operated wcrts i mm.clefiection per 2 volts at a distance of 6ocm. from the x;ibvator miyror.cl) The Characteristics oÅí the Counting Systen'}    Thc lineation oÅí the amplifying system ancl oscillog'raph as a wholexvas tested by inducin.cr a known voltage of any frequency on the firstvalve gr,ici and was fo"nd to be linear iip to i.scm. deflection at aclistance of 6o cni. froin the. vibrator inirror. IBy using poloniuin $ource,the Brag.'g's ionization relation xvas [c.stecl and founcl to be s.atisfactorilyfulfilled.    The prckcti,cal exaniples cftre rcprodizced in plate 1[.    In conclusion the authors wi.sh to express their cc)rclial thanks toProf. Dr. IEI. xN-, ral<atsu for his l<h: cl guldance and valuable-, suggestionsthroughout this xvork, and at the stune time their thanl<s are due to]LIattori' li.Iol<ol<xvai aiicl ] l•ippoiit (iakxijutsti S. kitl<okNvai foi" financial sup-port in this xvork.                           References   I. I-I. (lrekiachei' Z. S. f. ]1'hys., 36, 364 (ig26). .  2. C. IS. XVynn-XX: illiams and NVards, .II.'roc. Itoy. Soc. A 151, 3tJi (ig)3I>.                                           ' 3. J. R.. Dunning, .Rev. of Sei. Jnst., 5, 387 (ig34>•     S. I<iknchi a•nd I,I. Aol<i, Sc. ]?ap• I. ]?. C.R., 26, 36- (I93S>-     IR. Sagane, do, 27, 93 (i935)•  4. .B. iXral<atsu, I<. J<imura and 'Y. Uemura, t7N'Iem. of ]1"ac. oE ,SÅëi. an. cl tX.gt'icult. Tai-]io}<u 11mp. Univ. 8, 7S (rg36).  s. B. x'X.rakatsu, I<. .I<imura ancl Y. Uemura, Nat'ure 140, 77 (Ig37>.     I<. Isl imura, 2Nbstract of Researcli of l'Iattori ]{'okol"vai 4, IS5 (ig37)•     1<. INTimura, '] I.em. of College of Scl. I<. yoto I'mp. Univ. 22, 237 (I939)•                     Explanations of Plate l.    a- a-particles t'roin tlie iiattu`al stirface of 1'[oktttolite.        Cl.'he thicl<ness ef absorber: T3 ]nin. in air equivalent.        Cl'he depth of the ionization chainber: 7 ]nin.    b a-particles of !'o deposited on a copper plate.        [I'hc thickuess of al)sorber: 2oinn). in air equivalent,6cl(eK. Kimttra a'nd Y. b'em2tra., A Counting instrt{ment etc.                          '  Thg depth of tlie ionization chaniber: 2 nnn. q-particles oS 1)o deposited on a coppet" plate. The thickness of absorber: 3onun in air equivalent. Tlie clepth of the ionization chainber: 2 ]n]n.  1-lomog. eneous a-particles <r.2.7 cm) by the reaction : ]Li6+D:'-->2 }.ile4,    ]Li20-target>.  Tlie thickness of abs"orber: 8.3cin, in air equivalenL [ he depth of tlie ionization chamber: 2mm. Il7Iomogeneous a-particles (4.5cm.) by the reaction: P,ii+El.i-->Be"--I-Iea borax tarv.et). The thickness of al)sorber: 4cni. in {air equiva]ent.  '.{'he (lepth of the ionization chaniber: 4mii)•<thicl{(t},iickKiichi K:imura and Yoshzakt UemuraPlate Ia sl' l gtw-ny/t•'•'-'• ,,-Llt,/'L'T..- .t " - -...f'' si"L"tt- .::L"-si•a.aiua-".-'bpi'•[T•t' tlk';twta,stsLt..y" "'tirkSA'tset.!.=-•= .-.=- - .r-.- ...,...."a`-i-•;,/c''/ti.'t l." ' '-/ 'tttt. ''t'''t-L,=. X'V-:/''t '-"•-•h-,.-V'''•.- ' ..v-..-. tx" ..'t' rt;"'..J.v t.t. tt.t ttt ... ,.t-"- "'' imo ?..'.V-'T "-h.t.Ht,.tt T-e'-..r,t.'",.'-,r•'- t-t .ttt 'tt.lt.t"'1t.y.-`fyti,.  ;/'ng.. ,-1/'./t rt '.., ;•7-i'd."'-  .r•"Jlii-r-'l.''111,ll'l!!:!l:!ll!!ll:'     i'        ...:'sl',','t'-L;''- .'''"p-N'' '-,'-j'f'r.a-t',{ 1'Et-'-pt••,,iiiJib l.llelleelPP ,'''kIL'   s'''t "t.  . ":,Lf,-'"'t'e, 'T/,/1,W-. L, .- =,• '  ,,// ''":t: .' ti' ,i''/le'l,•..,ny- vpt rX.il•i

A Counting Instrument with Linear Amplifier

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A Counting Instrument with Linear Amplifier

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