Los alamos technical series volume i, experimental techniques part II ionization chambers and counters section a

APPROVED FOR PUBLIC RELEASE UNCLASSIFIED - chSSifiCa?tionC~oelled or (haged mn Mine !Citle Date LA - 1003 This document contains-ages VOL I EXPERlMENTAL TECXfNIQUM Part il Ionization Chambers and Counters Section A Written By : — r , p Bruno Rosei &“ns Staub ~ = —— — - = - 2’ –—-_—-.— ––— - - - - -E NOTE : IT IS PROPOSED THAT THIS IJOCUH.J3NT WILL BE ISSUED IN M EDITMD FORM AS PART OF THE LOS ALAMOS SECTION OF THE MANHATTAN PROJECT TECHNICAL SIRIIL’3 AT A SUBSEQUENT DATE IWUA.SWIED ‘*- APPROVED FOR PUBLIC RELEASE : —— ,- — — :.: , APPROVED FOR PUBLIC RELEASE r UNCIASSIFIE~ IJAMMTT,W PROJECT TECIiItlCAL “Comlu13U’TION OF L(25,;LAWS PROJWT - -.— The following niiterialILAybe subject to certain minor revisions in the event thut factual error; are discovered previous to final publications of this part c.fthe Technical Series Any such changes will be submitted fm- patent clearance and declassification in the usual”manner i ‘1 \ \, - UNCIA$SIFIED APPROVED FOR PUBLIC RELEASE APPROVED FOR PUBLIC RELEASE UNCLASSIFIED LM ALAMOS TECHNIG.4LSERIES VOL I - EXF’ERTWNTAL TECiiNIQUE3 PA9T 11 , CH.4PTW S ?’ CHAPTER BEHAVIOR OF FREE ELECTRONS AND IONS IN GASES OPERA’I’IWJ OF TW!ZiTION CHAMBERS ‘WITHCONSTANT IONIZATIC!N CHAPTER.10 OPERATION OF JONIZATICM Ci3Akt3ZRS WITH VA.RJABLE IONIZATIU’J CHAPTER 11 GAS MJLTTPLICATION CHAPTER 12 BErA-:RAY,J LR4Y, ~,’ID X-RAY DETECTORS CHAPTER 13 ALPHA PARTICLE DF,~QT@ CHAPTER 14 DE1’ECTOHSFOR NEUTRON !V3COILS C!i APTEt lj I) W’!?CTO.RS 07 n- & AND n-p ?tllACIICiJS CHAPTER 161 FIS51UN DETECTORS APPENDIX TO PART IT I)NC1A3SIFIED i APPROVED FOR PUBLIC RELEASE - APPROVED FOR PUBLIC RELEASE UNCLASSIFIED p~~e FOWfARD s.,.f .* * ,** -.s, ● ● 3EHAVIOR OF FRZZ EL!?C1’WNSA!J3ICJNSIN GASES.,, General Ccr~si4erati cms lhe ~ifi’~ision Zquatiofifcr Ions and filectponsin a -$ Jas Mean Free Path - E,wxy,vL0s3 i%r Collision, Mixture of Gases Experim~ntal Data Qelativeto Free Electrons Ekperimcntal Data ~e’ati.~eto Posjtive ad NeCattve Ions , APPROVED FOR PUBLIC RELEASE vi APPROVED FOR PUBLIC RELEASE Pafy.2 C?LUTE!{ 11 d&’5MGLTIPLJCAI’lCN ,.,*,, , .d ,,4,0 + 88, General Consider&6irms Experirwntal Values of the Gas h!ultiplica~ionfor ‘kriGus GasLW Puls.\Shape oi Proportional ~ounters Depc@ence of t}iePuJse Height on the Distance of’ the Track from the Wire 1:,5 End Effects~ Eccentricity of the ~’ire 11,6 Spread in P)JISPHei@t 11,7 MulLiFle “UireCpunter i2.1 Gmeral Considera$ions4 Discharge ~oun%~s and Intergratirifi Chambers 12.2 field of ~-%iy Dabectors 12,3 &sponse of a~lInte[!l”atir.g Chamber 12.4 Cylindrical d -Ray Ionization Chamber 12 Multiple Plate X-:layTcnizatian C@mber 12,.6 Multipk Plate ~-:3ay Ioniza+,icm‘hamlxw MC7 GsEwu14~y Ionization Chamter with Ciq Multiplicatif:n 12.8 GeiCer-Mueller Counters 1.2,y Mica ~inclm 2eiper-Mueller Counter 12,3.0Pulsed Cuunters CHAFW{ 13 CdAFTER 14 ALP:{AP.4~TIGLE3Ei’EC’fOIiS s, * .0.,.t ,, ● ● ● , * ● 12Ef’l?CK3S FOR NIXI!RCNRECOILS eQ *SC r ** SC ● ● ● ● ● 14.1 Introductory Cmsiderations 14,7 Genenl Prc’perti@sof Hydrogen ReccilChambers ]4,3 Ir.fiF~telyThin Solid %cliatar: Tcn Pulse ~:hamber, or E“~ct.rcnPulse Ciumber with hid, or Prc~crticr!alCounLer~ No fiqllCorrection 14.4 Infinitely-Thin %di.atcr; Parallei P’~te, Electron R~lse chamher~ No Wall Corrections 14.5 T}lin,Radiat.or$Par.~llelPlate Icn Pulse b%ambcr~ Electrcn Pulse Chamber with Grid, or Proport.icnalCo~nter$ No ‘WallCorrection ~1.ate,ElectrGn Pulse 14,6 Thin Radiator: Par,i13.el C~~mb&r; ;:o;YallCorrection is i APPROVED FOR PUBLIC RELEASE 1s6 172 APPROVED FOR PUBLIC RELEASE TA2LE CF CGN’I’ENTS (Cont ‘3,) Paqc 14.7 TlnickXadiator; Parallel Plate, Icn Pulse C.~amtw~, Electron Pulse chamber With Wilj, or Prc,pzrLjonal Counter~ No Fall Correcticm i 14.8 Gas Recoi1 dhambers NO Wall Effects 14.9 Gas Recoil, Icn Pulse Ghambert Compwtatim of Wali Effects 14.lC Uses of %co~l Chambers 14.31 i-IiCh Pr.sssure,Gas %ccii, Icm RJIW Chamlwr 14.12 ‘rhinRadiatcr, Electron Pulse, Parallel Plate Chamber 14.13 Thin Radiatort Electrcm Pulse Parallel Plate “ Double Chmbe r ~+,],4~a~ ,~~oii, cjclind~~al ch~ber 14,15 Gas -RecoilProport icnal Counter &c tron 1%l.se,Sphe~-i cal %amb er ~ 14.16 I%lck t?ac?iator, 14.17 Th ordinary then remains rising for fairly rapidly the is an irmrease o~e-of Lo point rate This with curve ccunter a pulse is as threshold We shall appreciably wire is discharges, of a the order the vert~i~al A A stationary by the of defleetin~ Wttern pulser counter a $-ray resembles The counting over a plateau normal a counters, In of 1X) microseconds of volwge, one-half the counting shape, tube, ccnmter define at which wiretsnd a sweep triggered to the He stiill rate The counter When tha the w:th by means of an W ccu~ling Yate in an individual counter constint counting @lee at ie wave cqn be varied cylinder divider wave had a width Geiger-Mueller value ccunter irl amplitude were made on a unit corltd.nlng 50 ~nfl~vhhal applied rmr wava is added may be connected the counting voltnge placed the normal ● 15 shows the Ly using t!!ese teat-a, the squ8re direct of the squara ap~ears to ob6erve plates FJgure The width to”tJ,e above 14 of 45@ vclts t’hrcugh a potefitisl of 1(X’O volte described uave voltage Ttiis square vG3taEe applied counters rate as a function source tk,e of the order ccrreaponding increases from zero The counting of 2C0 to 2X width, voltage define abcwa the voltage as breakdown n~~16 APPROVED FOR PUBLIC RELEASE of cna curw of aDout W volts volts of the at then which voltage to rate stirtu the the voltags APPROVED FOR PUBLIC RELEASE , c w m a m 0 m o 31 flNl W tt3d SlNfi09 APPROVED FOR PUBLIC RELEASE APPROVED FOR PUBLIC RELEASE M ‘ It is obviously de6irab10 that 611 the CCUfiMV3 of unit have CIOSely * the sams characteristics Btithat they can be oper~ted from thesame direct current supply Figure 16ahows threshold voltage and breakdown voltage for the fifty individual counters of the unit used It appears that the plateaus of the variou9 counters overlap over a comfortably wide range of voltiges Itm~y be pointed out th~t this result was achieved only after thorough cleaning of the counters %nd careful centering of the wiree When the r-ray source is removed, the ccuntillgrate en the plateau,for u 150 microsecomls about per hour gate drops from a value of abcut 13 a minute to a value of width, Slni:e the counters are @seal & times a second, this me8ns that the probeMlity for a spontaneous count to be recorded when the counter is pulsed ainoun+=to l/36C0 This background is s~j?=f c~erJtly s~g]~ fcJr~~1 FraCtica~ w~ose~> although it seems to be somewhat higher than that e=hected frcm cosmic raya and local radioactivity The counti~g yield of the counter ttibes counting rate witha known ~-ray source determining the at a known distance ald fGU~d tO bC Of @ the order of per cent This is close to the value which can be expected if all of the seconda”~ electrons penetr~t.ingthe tube give risa to a dischsrge It may be mentioned thnt pulsed ccunters can be made with metals other than platinum for the counter mll argon as (for instince brass or steel) and with”air inetesd of a ,gaafijling However, in these counters the background was found to be subnormallylarge and moreover dependent on the pist history of the counter COUnting rtit#3were reCOrdOd hmediRtely after the removal of strong Hi~h if-ray source; this spu.ricuscounting rate decreased gradually to the normal background in a period of the order of a half-hour Also the oFerating voltage was a function of th cGunter h~story An explanation fiorthe high counting rate after strong inadiation may be found itithe formaticn of metastibla molecules, an effect which is apparently minimized by the use of argon in a platinum counter APPROVED FOR PUBLIC RELEASE APPROVED FOR PUBLIC RELEASE ‘i!hreshold vo]ti~e ( “ ) and breakdown pulsed ecmnters for unit of fjfty vo~bge APPROVED FOR PUBLIC RELEASE ( O ) I , b ● ● ● 3SV8 APPROVED FOR PUBLIC RELEASE 3WL1OA APPROVED FOR PUBLIC RELEASE ● ... factual error; are discovered previous to final publications of this part c.fthe Technical Series Any such changes will be submitted fm- patent clearance and declassification in the usual”manner... the particiee In praotice, ~ and h can be detemlir.edas a function of c by measuring %and Gas a function of E~PO thrcugh for a. given gas Equations 13 and will then Frovide the functional relatj.cnbetween... Figures and 4) This fact, which was established thrcwgh experiments carried out at Los Alamos, is of con~iderable practical importance for the ccm~truct.ionof ‘fastllchambers The physical reason