A MASTER'S THESIS MASTER OF SCIENCE. Kenneth Edward Habiger. submitted in partial fulfillment of the. requirements for the degree

Transcription

1 THE MEASUREMENT OF THE FAST NEUTRON FLUX AT THE FAST BEAM PORT OF THE KSU TRIGA MARK II REACTOR by Kenneth Edward Habiger B. S., Kansas State University, 1964 A MASTER'S THESIS submitted in partial fulfillment f the requirements fr the degree MASTER OF SCIENCE Department f Nuclear Engineering KANSAS STATE UNIVERSITY Manhattan, Kansas 1966 Apprved bj Majr Prfessr /

2 UP ii J/ n TABLE OF CONTENTS Dcamtwr INTRODUCTION THEORY 1 4 The Neutrn Energy Spectrum frm Fissin f Uranium Fast Neutrn Scintillatin Spectrmetry 8 Neutrn Spectrum Unflding 10 Errr Analysis 14 EXPERIMENTAL FACILITIES 17 Equipment fr Pulse Height Analysis 20 Other Facilities 23 EXPERIMENTAL PROCEDURE 25 Adjusting the Linear Amplifiers and the Multichannel Analyzer...30 Adjusting the Variable Delay 33 Prcedure fr Taking Data 33 DISCUSSION AND RESULTS 35 Neutrn Spectrum Unflding Tests 35 P-Be Neutrn Spectra 39 Reactr Neutrn Spectra 46 CONCLUSIONS 57 SUGGESTIONS FOR FURTHER STUDY 59 ACKNOWLEDGMENT 61 LITERATURE CITED 62

3 . iii APPENDICIES.. APPENDIX A: Abslute Differential Efficiency as a Functin f Light Output (in "Cbalt" Units) fr Plane Parallel Mnenergetic Neutrns Perpendicular t Axes f 2" x 2" Diameter Cylinder f NE-213 Scintillatr 65 APPENDIX B: Descriptin and Explanatin f the IBM-1410 Cmputer Prgram Used fr Calculatin f the Respnse Functins '* APPENDIX Cs Explanatin f the Input Rutines fr the IBM-1410 Unflding Cde Being Develped in the KSU Department f Nuclear Engineering 80 APPENDIX D: Letter Received frm Oak Ridge Natinal Labratry Regarding KSU Data Analysis 82 APPENDIX E: Mdificatins in the B. J. Electrnics A8 Amplifier 86

4 iv LIST OF TABLES I. Prperties f Liquid NE «27 II. Optimum Phtmultiplier Vltage Determinatin III. Mdified A8 and Frte Resistance Ptentimeter Settings 29 IV. Lw Gain Test Spectrum Cntaining Tw Neutrn Energies 36 V. Lw Gain Test Spectrum Cntaining Eleven Neutrn Energies 37 VI. High Gain Test Spectrum Cntaining Twelve Neutrn Energies 38 B-I. Input and Output Parameters Required fr Executin f CONVERT.. 74 C-I. Input Rutines fr KSU Department f Nuclear Engineering Unflding Cde 81

5 . LIST OF FIGURES 1. Experimental and calculated uranium-235 fissin spectrum 6 2. Neutrn energy spectrum at the cre f the KSU TRIGA Mark II reactr 7 3. Abslute differential efficiency fr a 2" x 2" diam NE-213 scintillatr fr neutrn energies shwn Abslute differential efficiency fr a 2" x 2" diam NE-213 scintillatr fr neutrn energies shwn 13 5 Frte pulse-shape discriminatin circuit Detectr assembly and Frte pulse shape discriminatin circuit Pulse height analysis equipment Detectr assembly in frnt f cllimated beam prt Pulse heights frm P-Be and C gamma-rays vs. phtmultiplier tube vltage Test f amplifier linearity Lw gain P-Be cmplex neutrn spectrum Lw gain P-Be cmplex and smthed spectra High gain P-Be cmplex neutrn spectrum k Cmparisn f KSU P-Be spectrum t ORNL P-Be spectrum Unflded P-Be spectrum with theretical curve by Whitmre and Baker (23) One watt lw gain reactr cmplex spectrum One watt lw gain reactr cmplex and smthed spectra One watt high gain reactr cmplex spectrum 50

6 vi 19. Five watt lw gain reactr cmplex spectrum Five watt lw gain reactr cmplex and smthed spectra Five watt high gain reactr cmplex spectrum Five watt high gain reactr cmplex spectrum at 2400 phtmultiplier vlts Unflded 1 watt reactr neutrn spectrum with theretical curve f Janu and Dudek (12) Unflded 5 watt reactr neutrn spectrum with theretical curve f Janu and Dudek (12) Lgic diagram fr prgram used t calculate the respnse functins 76

7 vii NOMENCLATURE A Respnse matrix f the spectrmeter system t mnenergetic T A E C I neutrns Transpse f A Neutrn energy T A ta Unit matrix Greek Symbls 3 Neutrn flux p Number f cunts in a channel f a multichannel analyzer 2 u Mean square deviatin f p Weighting matrix

8 INTRODUCTION The ideal neutrn spectrmeter wuld have high efficiencies ver all neutrn energies, gd reslutin, be insensitive t gamma and beta radiatin, yield distinct lines fr mnenergetic neutrns, require simple electrnics, and be inexpensive. N spectrmeter yet develped has all these desired qualities. Several neutrn spectrmeters develped in the past have been successful in limited applicatins. Typical f these are the nuclear emulsin (2) and the hydrgen clud chamber (4). Bth displayed gd reslutin and fairly gd backgrund discriminatin, but were plagued with pr efficiency due t the tedius task f measuring neutrn track lengths. Ad els n et al. (1) described a hydrgen bubble chamber that was useful as a neutrn spectrmeter in the 5 t 30 Mev range, but with n inherent gamma discriminatin capabilities. The use f Lithium-Idide scintillatin crystals in the thermal neutrn range has been suggested by Price (18) wh ntes the high detectin efficiency f Lil in this energy range. Mrever, Murray (15) reprts favrable respnses f Lil t neutrns in the 1 t 14 Mev range. The main disadvantage f Lil as a neutrn spectrmeter is its high efficiency fr gamma radiatin. The He-3 prprtinal cunter is described by Batchelr et al. (3) as a suitable neutrn spectrmeter fr energies frm thermal t 1 Mev. Abve 1 Mev elastic cllisins between neutrns and He-3 nuclei becme imprtant and the ttal energy given ff by the interactin is n lnger linearly related t the energy f the incident neutrn. Hwever, the He-3

9 prprtinal cunter is nt sensitive t gamma-ray radiatin. Time f flight measurements have been applied in neutrn spectrmetry (16) with cnsiderable success in the lw t mderately high neutrn energies. Hwever, at energies abve a few Mev, time f flight displays pr reslutin due t inadequacy f flight time measuring equipment. Time f flight spectrmeters als suffer frm lack f a gamma discriminatin scheme. M. J. Ple (17) was ne f the first t describe a technique fr deriving neutrn spectra frm prtn recils in the inelastic scattering f neutrns. E. A. Elit et al. (9) als suggested the use f prtn recils in the stilbene neutrn spectrmeter. Bth f these methds relied n subtractin f backgrund t eliminate gamma radiatin and were, thus, generally inaccurate. Jhnsn and Trail (13) described a prtn recil spectrmeter system that was gd in the 2 t 20 Mev range, but was als sensitive t gamma radiatin. J. E. Draper (7) suggested a prtn recil spectrmeter capable f discriminating against gammas by a cincidence technique utilizing tw crystals. Hwever, the cincidence requirement resulted in very lw efficiencies, and the resulting neutrn pulse height distributin had t be analyzed, r unflded, t btain the true neutrn spectrum. It is evident that all the neutrn spectrmeters discussed abve are characterized by ne disadvantage r anther. The main disadvantages are sensitivity t gamma radiatin, pr efficiency, limited energy range, and in the case f prtn recil spectrmeters, difficult pulse height analysis.

10 . Recently, techniques have been develped that can circumvent the gamma radiatin prblem. Brek and Andersn (5) have reprted measuring neutrn spectra by the prtn recil methd in the energy range 1 t 10 Mev using stilbene crystals capable f pulse shape discriminatin t eliminate gammas. Stilbene has gd reslutin, but has the disadvantage f being nn-istrpic, s that its use depends n the rientatin f its axis with respect t the incident neutrns. Mre recently, Burrus and Verbinski (6) have investigated the use f the rganic scintillatr NE-213, which als is capable f pulse shape discriminatin. It has smewhat prer reslutin than stilbene, but des nt display a nn-istrpic character and has relatively high efficiency fr neutrns in the 0.5 t 14 Mev range. Burrus and Verbinski (6) als describe a methd f analyzing, r unflding, the resulting pulse height t btain the unscrambled spectrum. This unflding technique is based n the measurement f the respnse f NE-213 t at least tw mnenergetic neutrns (22) An NE-213 spectrmeter system similar t that f Burrus and Verbinski has been assembled at Kansas State University fr fast neutrn spectrum analysis. The purpse f the wrk described here is t develp perating prcedures fr this system, determine the system perating characteristics, and apply the system t the measurement f the fast neutrn energy spectrum f P-Be and f reactr neutrns at the fast beam prt f the KSU TRIGA Mark II reactr.

11 . THEORY The Neutrn Energy Spectrum frm Fissin f Uranium-235 Many nuclear reactins invlving the emissin f a light particle r gamma-ray had been carried ut prir t In that year, hwever, nuclear fissin was discvered while attempting t prduce transuranium elements by bmbarding uranium with lw energy r slw neutrns (14) We nw knw that the slw neutrn fissin prcess in uranium can be principally attributed t the istpe uranium-235, which is present t the extent f per cent in natural uranium (10). Uranium-235 fissin generally results in the prductin f tw fissin fragments f abut equal weight and, in additin, an average f 2.5 neutrns per fissin. The neutrns given ff in the fissin prcess can be classified in the fllwing manner: 1. prmpt fissin neutrns emitted within a few micrsecnds f the fissin event 2. delayed fissin neutrns emitted frm 3~ active fissin prducts. The delayed neutrns represent a small fractin f the ttal neutrns given ff and are generally gruped in energies belw 0.5 Mev. This is belw the energy range cnsidered in the present wrk and fr this reasn nly the prmpt fissin neutrns need be cnsidered. The prmpt neutrns given ff in uranium-235 fissin have a spectrum f energies ranging frm abut 0.25 t 18.0 Mev. The spectrum can be apprximated analytically by the expressin (19)

12 N(E) - /2/ire sinh *^E e" E where N(E) fractin f neutrns per unit energy range emitted per fissin E - neutrn energy in Mev. The uranium-235 neutrn fissin spectrum has als been measured experimentally. The measured spectrum presented by Gldstein (11) is reprduced in Fig. 1 alng with a calculated curve using the abve expressin. The neutrn spectrum ne wuld find in the cre f a reactr differs frm the true fissin spectrum due t interactin f the neutrns with absrbing and mderating materials present in the cre. The neutrn spectrum in any cre then depends n the nuclear prperties f the material in that cre. The principal materials in the TRIGA Mark 11 cre are uranium-235, uranium-238, aluminum, hydrgen, xygen, and zircnium. Janu and Dudek (12) have calculated the neutrn spectrum fr the TRIGA cre based n these materials using a P. apprximatin f the time-independent Bltzman equatin. The results f their calculatins are pltted in Fig. 2. Althugh the neutrn spectrum fr the TRIGA pltted in Fig. 2 has been calculated specifically fr the cre, it shuld be a very gd apprximatin t the spectrum at the fast beam prt. There is a vid in the reflectr between the cre and the fast beam prt. Thus, the nly materials that can attenuate the neutrns that eventually enter the fast beam prt are the thin reactr tank and the air in the prt. Sme scattering will take place in the prt, but if a cllimatr is used in making spectrum determinatins, the resulting spectrum shuld be that f an

13 1 \ Ml Experimental (11) Calculated (19) 10" 1 - X x i- 2 - u \ IO"* m IO" 5-10" 6 i i I 1 I l 1 1 \ () (1 E(Mev) Figure 1. Experimental and calculated uranium-235 fissin spectrum (11, 19)

14 10 v 10-1 w Energy (Mev) Figure 2. Neutrn energy spectrum at the cre f the KSU TRIGA Mark 11 reactr (12)

15 . : essentially, unc Hided flux. The spectrum determined in this wrk is cmpared t the spectrum calculated by Janu and Dudek (12) (see Fig. 2). Fast Neutrn Scintillatin Spectrmetry Neutrns are uncharged particles and d nt lse energy by direct inizatin f the matter thrugh which they pass. Hwever, neutrn detectin devices, like mst radiatin mnitrs, must be activated by inized matter; in the neutrn case the ins are prduced by a charged particle resulting frm a neutrn-nucleus interactin. Neutrn interactins that result in inizing charged particles can be classified in the fllwing categries (14) 1. the absrptin f a neutrn by a nucleus fllwed by the prmpt emissin f a fast charged particle 2. the absrptin f a neutrn fllwed by fissin f the absrbing nucleus 3. the scattering f a neutrn by a light nucleus, such as a prtn, with the reciling light nucleus prducing inizatin. The first tw interactins are mst cmmn t slw neutrns and, thus, will nt be cnsidered here. The last interactin, referred t as a "prtn recil" interactin, is mst cmmnly utilized in the detectin f fast neutrns and is the basis fr fast neutrn scintillatin spectrmetry. Detectin is based n nting the inizatin caused by reciling prtns prduced in the elastic scattering f neutrns by hydrgeneus materials T understand neutrn scintillatin spectrmetry, it is cnvenient

16 . t review the scintillatin prcess. The peratin f a fast neutrn scintillatin detectr can be divided int six cnsecutive events (18); these are: 1. scattering f a neutrn by a prtn in the scintillatr, with the prtn prducing inizatin within the scintillatr 2. cnversin f energy lst in the scintillatr t light energy thrugh the luminescence prcess 3. mvement f the light phtns t the phtcathde f the phtmultiplier tube A. absrptin f light phtns at the phtcathde with subsequent emissin f phtelectrns 5. multiplicatin f electrns within the phtmultiplier tube 6. analysis f the resulting current pulse frm the phtmultiplier tube with apprpriate electrnic equipment. The prtn recils prduced in the first event lse their energy by several different prcesses. The prcesses are cmplex and nt well understd, but are generally believed t include excitn migratin, sensitized flurescence, and phtn emissin and reabsrptin (18) The prcesses can be thught f as the transfer f energy frm prtn recils t scintillatr mlecules, the latter being transferred frm the electrnic grund state t an excited state. This excitatin energy is subsequently radiated as flurescent radiatin in the secnd event. As light phtns strike the phtcathde, phtelectrns are given ff in accrdance with the principles f phtelectrn emissin. These

17 10 phtelectrns are accelerated by a vltage gradient t a dynde where secndary electrns are given ff. Secndary emissin ccurs when electrns bmbard an electrn emitting surface such as cesium-ant imnide with an energy f apprximately 100 vlts. The verall amplificatin f a phtmultiplier is achieved by placing several dyndes in series where the secndary electrns frm ne dynde becme the incident electrns fr the next. The final step in the phtmultiplier prcess ccurs at the ande where the electrns are cllected. The resulting current pulse is led t a pre-amplifier, then t a linear amplifier, and finally t a multichannel analyzer. The spectrum btained frm the multichannel analyzer hwever, will nt be the true energy spectrum; phtmultiplier efficiency, instrument distrtin, and indirect neutrn-prtn cllisins with less than ttal energy cnversin will smear the true spectrum. The true spectrum must be "unflded" frm the smeared spectrum by spectrum analysis. A methd f unflding is presented in the next sectin. Neutrn Spectrum Unflding As described abve, the spectrum btained frm the scintillatin detectr and multichannel analyzer will nt be the true spectrum; limitatins in the system and cunting statistics will smear the true spectrum. The resulting cmplex spectrum must be analyzed r "unflded" t btain the actual spectrum. The unflding methd presented here was frmulated by Trmbka (21) fr the analysis f gamma-ray pulse height; this methd will be applied

18 11 t neutrn spectrum unflding since the principles are the same In bth cases. The number f cunts p. in any channel 1 f the multichannel analyzer-scintillatin detectr system expsed t a neutrn flux can be given by p. - I A, (E) 3(E) (1) x E where A.(E) - prbability that a unit intensity surce f energy E will result in a cunt in channel i 6(E) neutrn flux. The A. (E)'s are generally referred t as "respnse functins" and are the respnse f the detectin system t neutrns f energy E. Respnse f NE-213 liquid scintillatr has been measured and/r calculated fr 12 mnenergetic neutrn energies by Oak Ridge Natinal Labratry (22). These respnses are pltted in Figures 3 and 4. Equatin 1 can be re-written in matrix frm as P - A3 (2) r A3 - P. (3) Because f statistical errrs in the measurement f p, it is nt pssible t invert A and prceed directly t the slutin fr 3. Instead, a least squares slutin is used t minimize the effects f these errrs. The slutin fr 3 in the least squares sense can be btained by multiplying bth sides f Eq. (3) by the transpse f A. The slutin is

19 I i I #1 ibra ctru ^ I I l I 1 1 II J III II (light Pulse ciency "4-1 II ill i l l II t <u H 0) G 8 a > M 4J 9E 3 0) c c u *» J X ih - u & H IM > U 4J U 0) PI M i.-t rl 4J c ^r - I-l ih O (0 i-l CM ^ 1 > 1 m M H 1 H 3 <a H d 2" x.c CM 60 h ta 0} h fr l-l rl > S vo J "^ O mj"^ U a at M V IH th H > n <H i-t a u 3 h a O 5 w ja.e < CO N «en J* fh i I iii/ i/i r H O t-t 3fun 3ii3fx aa J ;U3A3 JO ^TTiqBqjj 1 a N 360 i_ O >-l H *M

20 r r 1 i i i hi 1 1 i i i i i m I i ' Pulse ill i I i i c in 1 1 i i i in i i i r > <M 13 m w H t 0) c a> c n u 3 CI c CN O u u 10 CO m 4J W m H Z c 3 e <A 4J th.c -a Ml X 4J r-j JC s 60 tn c hei a fr ncy H <u H O H u a m «m H c 4J M c a " vm 4) U 3 C ih 5.a n < II 1 1 I I XLLL 1 i H O 0) 3 00

21 14 B = (A T wa)" 1 Aup (4) where a weighting matrix u> has been included. The applicatin f least squares principles requires that the variance f each bservatin be the same. Since the variance in each element f p will be different, an attempt must be made t place equal variance n each bservatin. The diagnal weighting matrix u attempts t d this by letting w^ 2 2 l/; where is the mean square deviatin f p.. The calculatin described in Eq. (4) has been prgrammed by Eckhff and Hill (8) fr the IBM 1410 cmputer; this cmputer has mre than enugh capacity t handle the 12 mnenergetic neutrn pulse height spectra and 200 channels used in this experiment. Errr Analysis ^* Once the S's in Eq. (4) have been determined, it is pssible t calculate the mean square deviatin in 3. This calculatin is rather simple in the case where it is assumed that the A. 's (mnenergetic pulse height spectra) are knwn withut errr. Equatin 4 can be written as P n " KkkVi (5) ik where C T A ua r :jk " "i A «A ik. (6)

22 15 The inverse f C : is given by C - ; then CC" - I where I ls the identity matrix with elements I. and x 3. - jy (7) The elements f lljtl have the values V1 i j ' n I - It i 1 n. (8) The mean square deviatin (6 ) crrespnding t the deviatin n he written as in p. can 2 (B n ) HKj^Vik"i 2 '2<, i ) - ljk (9) 2 When w. - l/. (p ± ), Eq. (8) becmes (10) ijk. r 2(e n ) - Kn^VikV jk (ID Using Eq. (6): 2< v ^c ta c Jk (12) r Then frm Eqs. (7) and (8) '*<V fish^ (13)» 2 <V " 'ni- (14)

23 16 Equatin (14) states that the mean square deviatins in 3 are cntained n the diagnal f the C matrix. If the respnse matrix is knwn withut errr and the cunting time is the same fr all p.'s, the mean square deviatin in p. is given by 2 ( Pi ) - p ±. (15)

24 17 EXPERIMENTAL FACILITIES The liquid scintillatr used in this wrk is knwn as NE-213 (20); the liquid scintillatin detectr assembly is a 2 in. diameter by 2 in. high cylindrical glass cell cntaining 103 cc. f NE-213. Purchased frm the Harshaw Chemical C., the scintillatin liquid was dexygenated and encapsulated under nitrgen at the factry. One end f the glass encapsulatin cell is grund flat and plished fr ptical cntact. The upper prtin f the cell is cvered with a thin cating f diffuse white reflectr paint. NE-213 scintillatin liquid, prepared frm purified xylene, napthalene, activatrs and POPOP spectrum shifter, is designed fr internal cunting investigatins and frmulated t minimize the quenching actin f added materials. This scintillatr has pulse shape discriminatin capabilities similar t stilbene and is particularly useful fr neutrn cunting in the presence f gamma radiatin. Other prperties f NE-213 are shwn in Table I (20). Table I Prperties f Liquid NE-213 Density Refractive Biling Pt. Light Output Decay Cnstant Index (% Anthracene) Main Cmpnent

25 18 by Verbinski et al. (22) fr tw cylindrical cell sizes; this respnse is referenced t the light utput frm a C surce. "One Cbalt" is the pint at which the extraplated Cmptn edge fr the cmbined 1.17 and the 1.33 Mev C gamma spectrum crsses the abscissa. Respnse f NE-213 is shwn in Fig. 3 and Fig. 4 fr a 2 in. diameter by 2 in. high cell. The phtmultiplier and pulse shape discriminatin circuits used are duplicates f systems nw in use at Oak Ridge Natinal Labratry. An RCA type 6810-A phtmutiplier tube is used; a schematic f the pulse shape discriminatin circuit, r "Frte circuit", is shwn in Fig. 5 (reprduced frm a publicatin by ORNL (6)). A linear signal cntaining cmpnents frm bth neutrns and gammas is taken frm the 10th dynde f the phttube fr pulse height analysis. The ande signal is clipped using a delay cable and the negative prtin is fed t a summing netwrk where it is added t the psitive signal frm the 14th phttube dynde. This psitive signal cannt effectively vercme the negative signal in the case f a gamma ray, and the gamma ray pulse is canceled ut. The slw psitive pulse resulting frm a prtn recil, hwever, is t large t be canceled by the clipped negative pulse and the result is a net psitive pulse. This psitive signal, r gating pulse, admits neutrn cunts t the multichannel analyzer when it appears in cincidence with the linear signal; when the gating pulse is nt present the linear pulse is rejected and gamma ray cunts are eliminated. The scintillatr bttle is ptically cupled t the phttube with

26 L RCA 6810-A phtmultiplier 19 Cathde Grid 1 Dyn.l Dyn.2 50 k 20 k 20 k Dyn.3[ Dyn.4 20 k 20 k Dyn.5 24 k Dyn.6 27 k Dyn.7 33 k Dyn.8f 39 k Dyn.9f Dyn.lOf Dyn.llf 110 k -WAr 47 k 62 k 0.02 If- 75 k = 0.01 Linear utput Dyn.l2f Dyn.l3 Dyn.Uf Ande 91 k 0.02 If- If- 47 k llo k k AMr- s\. HV ~ vlts 91 k tt 0.02 tt 10 k 0.02 if: IF 2 1/2 in. HH2200 delay cable -*->! k * 20 k IN270 Figure 5. Frte pulse-shape discriminatin circuit

27 20 Dw Crning 10 centistkes silicne cmpund. A small prtin f the grease is placed n the end f the phttube; the scintillatr bttle is then placed directly n the grease and turned until all streaks and air bubbles are eliminated. The ptically cupled phttube and scintillatr bttle are then wrapped with black plastic electricians tape t insure a light-tight system. (See Fig. 6 fr a picture f the detectr assembly and Frte circuit.) Equipment fr Pulse Height Analysis As nted abve, a linear signal frm the 10th phttube dynde is used fr pulse height analysis. This signal is led t a B. J. Electrnics Mdel DA8 linear amplifier. During neutrn spectrum analysis the amplifier is perated at several different gains t btain ptimum reslutin fr bth high and lw energy neutrns. Amplified utput frm the linear amplifier is delayed 2 micrsecnds with a delay device; utput frm the delay device is led t the high level input f a TMC 256 multichannel analyzer with Mdel 210 pulse height lgic unit (see Fig. 7). The pulse shape discriminatr (PSD) utput is led t a mdified B. J. Electrnics Mdel DA8 linear amplifier. This amplifier is mdified t prvide a 10 vlt psitive pulse with a rise and fall time f 0.3 micrsecnds (see Appendix E). The psitive pulse is used t gate the multichannel analyzer. Linear and gating pulses must be in cincidence t eliminate gamma-ray cunts.

28 Figure 6. Detectr assembly and Frte pulse shape discriminatin circuit 21

29 Figure 7. Pulse height analysis equipment 22

30 23 Pwer required fr the PSD and phtmultiplier circuits is btained frm a Jhn Fluke Mdel 400BDA pwer supply; a regulated vltage is supplied t the amplifiers by a Beckman Vltage Regulatr, Mdel 760R. Other Facilities The very high vltages applied t the phttube require that the tube be shielded t prevent static nise pulses frm swamping the neutrn pulses. Tw cncentric metal cylinders, 10 inches lng, purchased frm the Magnetic Shield Divisin f the Perfectin Mica Cmpany, shield the phttube; these cylinders reduce the nise t acceptable levels. The inner cylinder is cnstructed f in. CO-NETIC AA material, and is 2 1/2" I.D.; the uter cylinder is cnstructed f in. NETIC S3-6 material and is 2 13/16" I.D. A 9/16" thick sheet f plyethylene separates the tw cylinders. During neutrn spectrum measurements the phtmultiplier and Frte circuit assemblies are munted n a stand (see Fig. 8); hrizntal and vertical adjustments f this stand are made t insure that the detectr is centered in the neutrn beam. The neutrn beam is cllimated t a 1 1/4" x 1 1/4" beam as it emerges frm the beam prt; the beam spreads t a 3" x 3" size 8' frm the exit pint. The detectr assembly is placed at the 8 ft pint t insure unifrm irradiatin f the 2" x 2" detectr.

31 Figure 8. Detectr assembly in frnt f cllimated beam prt 2k

32 25 EXPERIMENTAL PROCEDURE There are three pssible adjustments that can be made in the Frtephtmultiplier circuits; these variables must be prperly set if ptimum cunting is t be btained. The first adjustment t be cnsidered is the phtmultiplier tube vltage. If the applied vltage is t high, the tube will g int a state f saturatin when a high energy neutrn enters the detectr. This saturatin will distrt the high energy end f the neutrn spectrum, i.e. the highest energy neutrns will be cunted as neutrns f a lwer energy. If the applied vltage is t lw, the lw energy neutrn pulses will nt be detected and the lw energy end f the spectrum will be distrted. The ptimum phttube vltage is determined by pltting the rati f pulse heights f 4. A3 Mev P-Be gammas t the gammas f a C surce against phtmultiplier tube vltage. Phttube vltage is increased until the Mev gamma shws saturatin and the rati f pulse heights frm P-Be t C falls ff. The pulse height f the 4.43 Mev gamma is nted at this vltage. Tube vltage is then decreased until the 4.43 Mev pulse height is apprximately half f its saturatin value. This is a safe perating vltage fr 14 Mev neutrns, since they have pulse heights apprximately equal t that f 6.5 Mev gammas. The results f an adjustment f the type described abve are shwn in Table II and are pltted fr cnvenience in Fig. 9. Measurements were taken at 8 intervals f 100 vlts starting at 2000 vlts. The tube saturatin vltage was 2700 vlts; at this pint the 4.43 Mev gammas had a pulse height f 60 vlts. Operating vltage was set at abut

33 ffl ulse titmu 26 r^ CM vo > CM m ^-s a B) u.u 1-4 O g m > 6 CM a 00 MO «vo 4J i-( u > "O <u *r c fc CM u ca «u H a> th r-< S3 O d. 1 > ih 4-1 c- a H.a en 3 e a CM O 4J u «J U-l J-i V J5 «-H PL, U f-l 00 i-l H 4J CM CU <H CM h O Pm a O.H CM ON CM 0) H 3 t H N (s^ioa) ^us-faq. asin^

34 vlts where the pulse height f the A. 43 Mev gammas was 32 vlts, Table II Optimum Phtmultiplier Vltage Determinatin Phtmultiplier C 60 Pulse Height P-Be P-Be C vlts 10 vlts 4 vlts The secnd adjustment t be made is in the resistance ptentimeter grid f the phtmultiplier tube. This ptentimeter ptimizes the multiplicatin prcess f the phtmultiplier; it is adjusted using the multichannel analyzer t determine the ttal number f cunts recrded at a given ptentimeter setting. The equipment is turned n with the high vltage at 2300 vlts and given 4 t 5 hurs t warm up. The ptentimeter is then turned t the pint f minimum resistance and a P-Be surce is placed by the detectr. Finally the ptentimeter is adjusted fr ptimum cunting by setting it at the psitin that yields

35 28 the maximum number f neutrn cunts. The third adjustment is the resistance ptentimeter at the suming netwrk. This ptentimeter adjusts the height f the psitive pulses frm the 14th phttube dynde t effectively eliminate gamma ray pulses. It is nt necessary fr all f the gamma ray pulse t be remved at this pint; the baseline f the mdified A8 amplifier can be raised t eliminate pulses that have been partially canceled ut. Accrdingly, the adjustment f the summing netwrk resistance ptentimeter is made in cnjunctin with the adjustment f the pulse height selectr (Phs) n the mdified A8 amplifier. There are three bjectives t meet thrugh these latter tw adjustments, namely 1. maintainence f a 1000:1 gamma ray rejectin rati 2. acceptance f neutrn pulses dwn t apprximately 0.5 Mev 3. detectin f the highest pssible number f neutrn cunts. Adjusting the tw circuits t maintain the abve cnditins is accmplished by placing a C surce near the detectr s that the dse rate at the detectr is 2.5 t 3 mr/hr. The resistance ptentimeter is adjusted t an arbitrary psitin and the Phs f the Md. A8 amplifier is raised until a gamma ray rejectin rati f 1000:1 is nted. Gamma rejectin ratis are measured with the multichannel analyzer; cunts are recrded fr a perid f time in bth the anti- cincidence and cincidence mdes. The rati f ttal cunts frm the anti- cincidence run t the ttal cunts in the cincidence run is the gamma rejectin rati. Rejectin ratis are measured at tw linear amplifier gains: a

36 29 high gain with "1 cbalt" in channel 200, and a lw gain with "1 cbalt" in channel 20. The next step is t replace the C with a P-Be surce and cunt fr a perid f time with the multichannel analyzer in the cincidence mde. Particular attentin is given t the shape f the spectrum, nting the channel where the peak ccurs. T insure detectin f neutrns with energies as lw as 0.5 Mev, this peak must be in the 10 t 20 channel range during high gain peratin. Spectrum distrtin can be checked at the lw gain; a hump in the trailing edge f the spectrum will ccur if the resistance f the ptentimeter is t high r if the Phs setting is t lw. Prper settings f the resistance ptentimeter and the Phs are thse that yield a P-Be spectrum peak in the lwest pssible channel withut distrtin. An example f this type f adjustment is shwn in Table III fr phttube vltages f 2300 and 2400 vlts. The higher vltage results in settings that yield a P-Be spectrum peak in a lwer channel; hwever perating at this vltage runs the risk f phttube saturatin. Table III Mdifier A8 and Frte Resistance Ptentimeter Settings Md. A8 Phs P-Be Peak Resistance Ptentimeter Vltage High Gain Lw Gain Channel Turns ut frm full in / /8

37 30 Adjusting the Linear Amplifiers and the Multichannel Analyzer The signal frm the Mdified A8 amplifier is used as a gating pulse input t the multichannel analyzer fr cincidence requirements. It is necessary, hwever, that fur pulse cnditins be satisfied t meet the input specificatins f the multichannel analyzer and still prvide the best pssible cincidence efficiency. The pulse must be psitive, have a height f abut 8 t 10 vlts, have a rise and fall time f apprximately 0.3 micrsecnds, and be relatively wide. Amplifier mdificatins prvide fr tw Phs utputs, ne negative and the ther psitive t achieve this; the fine gain cntrl has been remved frm the mdified system. Multichannel analyzer (abbreviated MCA) gating requirements can be met by perating the Mdified A8 amplifier at a gain f 2 and by using the psitive Phs utput. The negative Phs utput is useful in adjusting the system. Amplified utput frm the cnventinal linear amplifier is checked fr linearity using a precisin pulser and an scillscpe. Heights f input and utput pulses are measured n the scillscpe at a particular amplifier gain. The results f a measurement f this type are pltted in Fig. 10; it can be determined that the amplifier is linear within 1.5%. It is necessary t perate the cnventinal linear amplifier at bth a lw and a high gain if the entire range f neutrn energies frm 0.5 t 14 Mev is t be studied. The high gain setting is s chsen that 1 cbalt is lcated in channel 200; lw gain is set at ne-tenth f the high gain, in rder that 1 cbalt is placed apprximately in channel 20.

38 i > - «0 4J i-l O > u 3 a. g 30 / /ill C Input (vlts) Figure 10. Test f amplifier linearity

39 32 High and lw gain adjustments are made by feeding a pulse int the linear amplifier with a precisin pulser and nting the multichannel analyzer (MCA) channel crrespnding t this pulse. Fr a factr f 10 change in gain adjustment, gain settings n the linear amplifier are adjusted until the pulse is being stred in the apprpriate channel, i.e. displaced a factr f 10 frm the previus setting. The nly adjustment made n the MCA is the baseline setting; it is set s that a plt f pulse height vs. channel number will have channel zer equal t zer vlts. This peratin is als carried ut using the precisin pulser. The pulser utput is adjusted until the pulse shape resembles as clsely as pssible the neutrn pulse shapes being analyzed. This pulse is led t the linear amplifier, and then t the high level input f the MCA. The gain n the linear amplifier is adjusted t place the pulses in channel 250. The pulse magnitude is then reduced by a factr f 10; the resulting pulses must fall in channel 25 if the plt f input pulse height vs. channel number is t g thrugh zer. This adjustment is checked at regular intervals t prevent zer drift. A final check n the cnventinal linear amplifier and MCA adjustments is made with a C 60 surce. The amplifier is adjusted t the high gain setting and a C 60 surce is cunted fr a perid f time with the MCA in anti-cincidence mde. The run is repeated at the lw gain setting fr the same cunting perid; gain adjustements are made with the precisin pulser as described abve. The high gain utput is then pltted vs channel number. The lw gain utput is pltted n the same scale with channel 1 as channel 10, channel 2 as channel 20, etc.,

40 33 and with the number f cunts in a given channel reduced by a factr f 10. The tw plts shuld fall apprximately n ne anther if all adjustments have been made crrectly. If either the gain r baseline settings are nt prperly adjusted, the plts will nt cincide. Adjusting the Variable Delay A certain amunt f delay is required in the linear amplifier utput led t the MCA if the gating input is t be prperly timed with respect t this linear amplifier signal. MCA specificatins shw that it is necessary that the gating input pulse precede the pulse being analyzed by a few tenths f a micrsecnd. A trial and errr prcedure is used t determine the prper delay as an alternate t an exact direct measurement. The prper delay is determined by cunting a P-Be neutrn surce at the tw linear amplifier gain settings with an arbitrary amunt f delay in the line between the MCA and the linear amplifier, and the MCA in the cincidence mde. These data are pltted n the gain vs channel number plt described abve. If the plts fall n each ther, the prper delay is in the line. If nt, a new delay setting is tried in the manner nted abve until a prper setting is achieved. The prper delay fr this wrk is 2.0 micrsecnds. Prcedure fr Taking Data Tw surces f neutrns, including P-Be and reactr neutrns, are analyzed in each experiment. The P-Be neutrn surce is used t adjust

41 . 34 the equipment as described abve. Als, since the P-Be neutrn spectrum has been determined previusly by ther wrkers, this spectrum is determined first and used t check the reliability f the cunting system. The prcedure used in determining P-Be data begins with an adjustment f the linear amplifier gain t place 1 cbalt in abut channel 200. The surce is then placed near the detectr and cunted lng enugh t get gd cunting statistics. At the end f this time the gain is reduced by a factr f 10. The neutrn surce is nt mved during this time; the surce is then cunted fr the same length f time used in the high gain determinatins. The prcedure fr taking the reactr neutrn spectrum data is similar t that used fr P-Be except that the detectr is placed in frnt f the beam prt with the cllimatr in place. The detectr is placed 8 feet frm the end f the cllimatr t insure that the beam is spread enugh t irradiate the detectr unifrmly and als t reduce gamma-ray backgrund. A C 60 spectrum can be taken with the detectr in frnt f the beam prt and with the reactr in peratin if the lead shutter in frnt f the prt is clsed t cut ff reactr neutrns and gamma-rays

42 35 DISCUSSION AND RESULTS Neutrn Spectrum Unflding Tests The respnse functins fr mnenergetic neutrns are relatively smth as cmpared t the phtpeaks present in the respnse functins fr mnenergetic gamma rays. Fr this reasn cmplex neutrn spectrum unflding using a least squares technique might be mre difficult than in the gamma-ray case. Originally designed fr gamma spectrum unflding, the unflding methd described in the preceding sectin was tested fr its applicability t neutrn spectrum unflding. The respnse functins used fr analyzing the lw gain data were cmbined in tw different grups and used as data t test the lw gain unflding cde. In the first case the 9th and 10th respnse functins, crrespnding t 5.97 and 8.12 Mev 4 neutrns, respectively, were multiplied by 10 and added tgether t frm a "cmplex spectrum". The 9th and 10th respnse functins were chsen because they were quite similar; this similarity made them the hardest t unfld frm a cmplex spectrum. The unflding cde successfully eliminated the 1st eight neutrn energies (see Table IV), but culd nt entirely eliminate the 12th energy. Hwever, the calculated magnitudes f the 9th and 10th energies matched -4-4 the actual quantities within 0.84 x 10 and 6.58 x 10 %, respectively. The secnd lw gain test spectrum included a cmbinatin f the 4 1st 11 respnse functins, each multiplied by 10. The resulting cmplex spectrum was analyzed frm channel 9 t channel 102; this apprximated

43 36 Table IV Lw Gain Test Spectrum Cntaining Tw Neutrn Energies Amunt Present in Calculated Amunt Errr in N E(Mev) Cmplex Spectrum Frm Unflding Cde Calculated Amunt x 10* X x x X x X x 10 3 actual cnditins encuntered in this research. In analyzing actual cmplex spectra the lwer channel limit is at the peak f the cmplex spectra and the upper channel limit is the channel where the spectra first g t zer. The results f the secnd test spectrum analysis are shwn in Table V. The first 4 energies were eliminated as expected since their respnse fell belw channel 9, which was the lwest channel number analyzed. The

44 37 Table V Lw Gain Test Spectrum Cntaining Eleven Neutrn Energies Amunt Present in Calculated Amunt Errr in N E(Mev) Cmplex Spectrum Frm Unflding Cde Calculated Amunt x x x x x x x x x x x x x x x x x x x x x i x x x i x x i 2 magnitude f the 5th energy present was t large. This can be explained by the fact that the respnse fr the 5th energy ends in the 9th channel. Thus, nly ne channel (channel 9) f the analyzed data cntained a respnse fr the 5th energy; an accurate determinatin f the amunt f the 5th energy present wuld nt be pssible with just ne channel. As in the first test, the 12th energy was nt entirely eliminated. The abve lw gain unflding tests indicated that little faith can

45 be placed in the accuracy f the results btained fr bth the 12th and the lwest accepted energy. Hwever, the tests shw that results fr intermediate energies shuld be accurate within apprximately.0007% (the largest single errr in the calculated amunts) A test <f the unflding technique at the high gain was perfrmed 4 by multiplying all 12 neutrn energy respnses by 10 and cmbining t frm a cmplex spectrum. The unflded results are shwn :Ln Table VI and were btained by analyzing frm channel 22 t channel 200. The large Table VI High Gain Test Spectrum Cntaining Twelve Neutrn Energies N E(Mev) Amunt Present in Cmplex Spectrum Calculated Amunt Frm Unflding Cde Errr in Calculated Amunt x x x x IO x x x x x x 10 4 x x x x x x x x x x x x x i x x x i x x x i x x x i x x x i 2

46 39 errr in the first tw energies can be attributed t the channel 22 cutff; nly a very small prtin f the respnse fr these tw energies is seen by the cmputer. P-Be Neutrn Spectra A P-Be neutrn spectrum was recrded at a high and a lw gain; these spectra were then analyzed with the previusly described unflding cde. The lw gain cmplex spectrum is shwn in Figs. 11 and 12 and the high gain cmplex spectrum is shwn in Fig. 13. The P-Be lw gain cmplex spectrum was characterized by a "peaking" effect in the channel 70 t 100 regin. A peak was recrded in this regin interrupting a spectrum that, therwise, descended smthly frm apprximately 15,200 cunts in channel 4 t zer cunts in channel 135. This peaking effect ccurred after raising the phttube perating vltage t 2300 vlts and after adjusting the resistance ptentimeter f the Frte circuit. These adjustments were made in an attempt t shift the high gain P-Be spectrum peak t the lwest pssible channel and, thus, detect neutrns with energies as lw as 0.5 Mev. The assumed prbable cause fr this peaking effect was the detectin f high energy gamma-ray cunts. A C surce was cunted in cnjunctin with the P-Be surce t test this assumptin; the magnitude f the peak increased sharply while the rest f the spectrum was unchanged. Apparently, at a phttube vltage f 2300 vlts and at certain ptentimeter settings, Frte circuit gamma-ray discriminating capabilities are impaired, allwing gamma-ray activity t be recrded.

47 * i i g t * 8000 I 6000» () Channel number. Figure 11. Lw gain P-Be cmplex neutrn spectrum

48 Cunts t ^ i 180. Cmplex Spectrum., % # Smthed Spectrum 160 * 140 t, ' 120 -;'* m c I * per «00 ON V. - ( Channel number Figure 12* Lw gain P-Be cmplex and smthed spectra

49 \ i ^Tj^ 1 i umber Channel i 42 1 T" 1i i CM H O vo f 140 n 12 e 3 h.v' Y< f: O a t c M «J 3 i S 0) th D. E O u n P* H *. ' <N.. H a c. r 1. H 00 m CM 0» M9 r» CM 1-4 ' «H Xauuetp add s}un3 u 360

50 . 43 Data were recrded at these "verlad cnditins" with a sacrifice in accuracy at the higher channels t describe as much as pssible f the lw energy neutrn spectrum. The spectrum was smthed (see Fig. 12) in the peaking regin with a "nn-peaked" P-Be spectrum which had been recrded at a lwer phttube vltage and a different ptentimeter setting. The P-Be lw gain spectrum was cmpared with a P-Be spectrum btained with the ORNL NE-213 spectrmeter system (see Fig. 14). The ORNL spectrum was nrmalized t the spectrum measured here at channel 10. Remaining pints were within at least 5% f the ORNL spectrum, indicating gd similarity between the tw systems at high neutrn energies (lw gain) An unflded P-Be spectrum (see Fig. 15 fr results and theretical P-Be spectrum f Whitmre and Baker (23)) was btained frm the lw and high gain spectra. Unflding technqiues fr the lw gain spectrum were cmpleted withut difficulty; hwever, a satisfactry unflded high gain spectrum was nt btained. When analyzing the high gain spectrum, the unflded least squares slutin retained sme energy values (pltted in Fig. 15), but rejected intermediate values; this is nt acceptable since P-Be is knwn t have a cntinuus neutrn energy spectrum. An attempt was made t unfld the high gain spectrum using 22 mnenergetic neutrn spectra rather than 12; the additinal 10 mnenergetic spectra were btained by extraplating between the 12 available spectra. This attempt was als unsuccessful. The failure t unfld the high gain spectrum is cncluded t result frm a small difference in the mnenergetic neutrn respnse f the

51 \, V I I I < O KSU data (selected I channels) 1 ORNL data r-t 1 <U l 1 c i «i X 1 Q 8000 Jj \ <u \. \ 4J 6000 U T \ \ 4000 V 2000 ^^x ) Channel number Figure 14. Cmparisn f KSU P-Be spectrum t ORML P-Be spectrum

52 45 10" O High gain pints O Lw gain pints Nrmalized theretical curve % 5 & i<r tn e u a i<r 6 E(Mev) Figure 15. Unflded P-Be spectrum with theretical curve by Whitare and Baker (23)

53 46 system used in this wrk cmpared with respnse f the ORNL system. Apparently, n grss differences exist since the lw gain spectrum match the ORNL lw gain spectrum within at least 5% (see Fig. 14). The difference is mst prbably in the reslutin f the systems; difference in reslutin wuld nt be apparent at the lw gain, but culd be significant in the high gain (high spectrum reslutin regin) Burrus and Verbinski (6) determined the "fractinal reslutin" f the ORNL system by "dividing the difference in pulse height between the 88% pint and the 12% pint f the upper edge f the pulse-height distributin (in suitable pulse-height units) by the pulse height f the 50% pint". A cmparable reslutin measurement with the KSU system is nt pssible since the peak f any ne neutrn spectrum (lwer channel cutff pint) fr this system falls in a different channel than that f the ORNL system. Identical spectra fr the tw systems will have peaks f different magnitude due t this difference in lwer channel cut-ff; this prevents a cmparisn f reslutin as determined by the ORNL methd. Reactr Neutrn Spectra Reactr neutrn spectra were recrded at lw and high gains fr reactr pwer levels f 1 and 5 watts (see Figs. 16 t 22). The detectr assembly was psitined 8 ft. frm the end f the cllimatr at the fast beam prt as discussed in a preceding sectin. As nted with the P-Be spectra, the lw gain reactr neutrn spectra were unflded with reasnable results; attempts t unfld the high gain neutrn spectra were again unsuccessful. Gamma peaking in the lw gain

54 47 data was smthed with the use f spectra recrded in the absence f peaking. Results f the lw gain unflding are shwn in Figs. 23 and 24 with the curve predicted by Janu and Dudek (12); several high gain pints are als shwn. One high gain spectrum was recrded at a phttube vltage f 2400 vlts. The higher phttube vltage made it pssible t detect neutrns f lwer energy; but n significant imprvement in the unflded results was btained. a

55 \ ' 1 t j UUU» i» I i II C c u 3000 M 41 C3 u Channel number Figure 16* One watt lw gain reactr cmplex spectrum \ a

56 Cmplex spectrum X Smthed spectrum c «j j= u «- 60 J ' 20 ***** ****** 40 J Channel number ^**K<^$tM^fr.m 1mm tn X* Figure 17* One watt lw gain reactr cmplex and smthed spectra

57 1 ( - i i \ number hannel ctrura J \ "HT" 1 f 1 1 / 200 ;V : ( i.,v /: ::* X m v. V Q. 6 u.:- M >. O \ u m. U. u «/ c J 100 «O D. 0) 60.. ; : -. H J3 41-4J (4 5 \ '.... CM.» V c CO u IN i 00 SO -* CM 1 H -[auuetp lad siun fi

58 , i i i i n^ ih c C M» % u *. * Channel number Figure 19. Five watt lw gain reactr cmplex spectrum

59 V T" "I" "T~ T~ i^ ^^ Cmplex spectrum 160 % Smthed spectrum ih % c M. U ,-.' M C *J 4» 60 A 40 ft 20 1 p ' () Channel number Figure 20. Five watt lw gain reactr cmplex and smthed spectra

60 * 1, ( r 53 1 nr* T" HP T" i i," i 00 i O *./ / 1 I a - #* JO 1 u.- 3 ej e. \ \.., O > - O V X. ih C 01». c f-t 9 M (X e 3 u u #" m. 00 u 1 u c H CO 9 60." * J=.e CO H - a).. > rh * '."... <s V M9DO «J i i i I I c c u -> f «n IN CM i"i»1 Xauueq jad s^anq.c IM

61 \ ) i *. v 19 annc 54 hh " r T" T" 3 r«4 i :- O 30 H CO 4J O > t U V H O r-l D. r -H 4J ih. 3» vd H.* / O y u.>.c O p. H CM O B i-t CU 3../. > M s 4J 3 (J ; B { O. ; H (A i-t.} JC B. y u S <.' M O *J *.} a.» «-../, c H «bo.c t H.e 4J ft «0 a «* > 1 '. 01 % * > ' \ tb H L CI CM CM a* u 300 H K i i m ' B" U ' c > Cs_a \0.«00 cm * e> Xeuusip a ad B^un^ «

62 II i i i i i i. O High gain pints V. O Lw gain pints "" Theretical curve nrmalized >. fr best fit > *-> C t * n 1 * $\ : \ - - uu3 SB 10* - ^k i. K - m i () E(Mev) Figure 23. Unflded 1 watt reactr neutrn spectrum with theretical curve f Janu and Dudek (12)

63 i. «f ^v O High gain pints \. Lw gain pints \ Theretical curve nrmalized " I \ \ fr best fit 10- > i C rl e *^» (0 M «J 3 0) 2 10* " - XT" \ I 1 1 II E(Mev) Figure 24* Unflded 5 watt reactr neutrn spectrum with theretical curve by Janu and Dudek (12)

64 57 CONCLUSIONS Respnse f the NE-213 spectrmeter system used in this wrk t neutrns in the 2 t 14 Mev energy range (recrded at lw gain) was evidently very similar t the system at ORNL. Lw gain P-Be cmplex spectra were nearly identical (within at least 5%) t ORNL P-Be cmplex spectra; the ORNL data have been successfully unflded and agree with the generally accepted spectrum f Whitmre and Baker (23) (see Appendix D). Respnse f the system t lw energy neutrns was imprper. N grss malfunctin is suspected t exist since this wuld be evident in the lw gain data. The errr is prbably in the reslutin f the system; reslutin errrs wuld be mst significant fr the high gain spectrum when the spectrum is spread ut in fine detail. Pr reslutin may result frm a lack f prper ptical cupling between the scintillatr bttle and phtmultiplier tube. The scintillatr bttle is jined t the phttube with Dw Crning 10 centistkes silicne cmpund. All streaks and air bubbles in the grease must be eliminated fr prper cupling and gd reslutin. Since, as nted earlier, the bttle is cated with a white reflectr paint, it was nt pssible t determine directly if all streaks and bubbles were eliminated during the cupling prcedure. The NE-213 spectrmeter system did nt detect neutrns in the 0.5 t 2.0 Mev energy range withut a peaking effect in the lw gain spectra. The peaking effect was nt apparent when detecting neutrns with energies frm 1 t 14 Mev. Hwever, as adjustments were made in phttube vltage

65 58 and Frte circuit resistance ptentimeter settings t extend the detectable neutrn energies t 0.5 Mev, peaking in the lw gain spectra was nticed. Evidently, the phttube and ptentimeter adjustments caused the gamma discriminatr circuit t fail and higher energy gamma rays were detected and cunted. There were n bvius explanatins fr the failure f the gamma-ray discriminating circuit. The failure may be caused by a pr electrnic cmpnent in the circuit r by an imprper Frte circuit adjustment. In any case, the failure did nt cmpletely invalidate the results f this wrk; the peaking effect culd be eliminated with the aid f "nn-peaked" spectra.

66 59 SUGGESTIONS FOR FURTHER STUDY Neutrn energy reslutin f the NE-213 neutrn spectrmeter system used in this wrk can be imprved by replacing the white reflectr paint n the scintillatr bttle with aluminum fil (shiny side in). A similar substitutin at ORNL (6) reduced the reslutin frm 11 t 6.5%. Imprved reslutin may make it pssible t unfld high gain cmplex neutrn spectra. Electrnic cmpnents f the pulse shape discriminatr circuit shuld be thrughly examined fr defective parts. Operatin at high vltages may require that certain cmpnents be shielded r relcated t prevent interference with ther cmpnents. The respnse f the system used in this wrk t mnenergetic neutrns shuld be checked by expsing the detectr t mnenergetic neutrns prduced with the Kansas State University Nuclear Engineering heavy particle acceleratr. Several different neutrn energies are available frm this acceleratr. Using these mnenergetic spectra, factrs can be determined t crrect the mnenergetic ORNL respnse functins. Further, it wuld be desirable t develp a cmplete library f experimentally determined mnenergetic respnses. These respnses wuld be characteristic f the KSU system and wuld be expected t give better results than can be btained with the ORNL system characteristic functins. Further applicatins f the NE-213 neutrn spectrmeter used in this wrk are numerus. Fellw student, Capt. James Kapitzke, is presently measuring fast neutrn dse albeds using this system. Gale Simns, Grad-

67 60 uate U.S.A.E.C. Fellw, has prpsed the use f this system fr experimentally determining mnenergetic neutrn crss sectins.

68 61 ACKNOWLEDGMENT The authr wishes t express his gratitude t Dr. Walter Meyer under whse directin this study was accmplished. Special thanks must als g t Dr. C. E. Cliffrd f Oak Ridge Natinal Labratry wh suggested the study. Sincere appreciatin is als extended t Dr. W. R. Kimel, Head f the Kansas State University Department f Nuclear Engineering, fr his encuragement and crdinating effrts with ORNL, and t the Kansas State University Engineering Experiment Statin fr their financial supprt. Recgnitin must als be given t fellw students, Capt. James Kapitzke and Gale Simns, Graduate U.S.A.E.C. Fellw, fr their cntributins, and t Dean Eckhff, Nuclear Engineering staff member, fr his assistance with the unflding cde.

69 62 LITERATURE CITED 1. Adelsn, Harld E., Hyt A. Bstick, Burtn J. Myer, and Charles N. Waddell Use f the Fur-Inch Liquid Hydrgen Bubble Chamber as a Fast- Neutrn Spectrmeter. Rev. Sci. Inst., 31: 1 (1960). 2. Allred, J. C, A. H. Armstrng and L. Rsen The Interactin f 14-Mev Neutrns with Prtns and Deuterns. Phys. Rev., 91: 90 (1953). 3. Batchelr, R., R. Aves and T. H. R. Skyrme Helium-3 Filled Prprtinal Cunter fr Neutrn Spectrscpy. Rev. Sci. Inst., 26: 1037 (1955). 4. Bnner, T. W., R. A. Ferrell and M. C. Rinehart A Study f the Spectrum f the Neutrns f Lw Energy frm the Fissin f U^ 5. Phys. Rev., 87: 1032 (1952). 5. Brek, H. W., and C. E. Andersn The Stilbene Scintillatin Crystal as a Spectrmeter fr Cntinuus Fast-Neutrn Spectra. Rev. Sci. Inst., 3_1: 1063 (1960). 6. Burrus, W. R. and V. V. Verbinski Recent Develpments in the Prtn-Recil Scintillatin Neutrn Spectrmeter. Trans. Am. Nucl. Sc, 1} (1964). 7. Draper, J. E. A Fast Neutrn-Scintillatin Spectrmeter. Rev. Sci. Inst., 25: 558 (1954). 8. Eckhff, N. D. and T. R. Hill Persnal Cmmunicatin. Department f Nuclear Engineering, Kansas State University, Manhattan, Kansas. 9. Elit, E. A., D. Hicks, L. E. Beghian and H. Halban Inelastic Scattering f Neutrns. Phys. Rev., 94: 144 (1954). 10. Glass tne, Samuel and Miltn C. Edlund Nuclear Reactr Thery. D. Van Nstrand Cmpany, New Yrk (1962). 11. Gldstein, Herbert The Attenuatin f Gamma Rays and Neutrns in Reactr Shields. Nuclear Develpment Crpratin f American, New Yrk (1957) 12. Janu, G. D. and J. S. Dudek Gam-1: A Cnsistent?i Multigrup Cde fr the Calculatin f Fast Neutrn Spectra and Multigrup Cnstants. GA-1850.

70 Jhnsn, C. H. and C. C. Trail Prtn-Recil Neutrn Spectrmeter. Rev. Sci. Inst., 27: 468 (1956) 14. Kaplan, Irving Nuclear Physics. Addisn-Wesley Publishing Cmpany, Inc., Reading, Massachusetts (1963) 15. Murray, R. B. Use f Li 6 I(Eu) as a Scintillatin Detectr and Spectrmeter fr Fast Neutrns. Nuc. Inst. Meth., 2: 237 (1958). 16. Neilsn, G. C. and D. B. James Time f Flight Spectrmeter fr Fast Neutrns. Rev. Sci. Inst., 26: 1018 (1955). 17. Ple, M. J. Neutrn Flux and Spectrum Measurement. Prc. Phys. Sc. (Lndn), -65: 453 (1952). 18. Price, William J. Nuclear Radiatin Detectin. McGraw-Hill, New Yrk (1964). 19. Rckwell, Thedre, ed. Reactr Shielding Design Manual. D. Van Nstrand Cmpany, Princetn, N. J. (1956). 20. Scintillatr Catalgue. Nuclear Enterprises, Ltd. Cleveland, Ohi. 21. Trmbka, J. I. Least-Squares Analysis f Gamma-Ray Pulse-Height Spectra. NAS-NS Verbinski, V. V., J. C. Curtney, W. R. Burrus and T. A. Lve The Respnse f Sme Organic Scintillatrs t Fast Neutrns. ORNL-P Whitmre, B. G. and W. B. Baker The Energy Spectrum f Neutrns frm a P-Be Surce. Rev., 78: 799 (1950). Phys.

71 APPENDICIES 64

72 65 APPENDIX A Abslute Differential Efficiency as a Functin f Light Output (in "Cbalt" Units) fr Plane Parallel Mnenergetic Neutrns Perpendicular t Axes f 2" x 2" diameter Cylinder f NE-213 Scintillatr

73 s- <f CO UN O m I 66 > <t in c c rh d1 CO CO r-l m \0 r-l in CO On CO in n UN CO CO On CO NO <r UN ; UN r-l UJ CO 1 CNJ ON CO On <t rh O ON s- I in rh i-h CO O ON Is cm <r i-h tt r- UN CO <* r-i s: 00 CM O H0>0 H- CM rh <t CO rh On On CM m c CN 00 vo s- I CO t-i CM UN r-i i-h CO r-l m in c CO ON CM c CM O CO cc <t c c s- I r^ <f vo CO CNJ UN t> UN OvJ rh CO CO O rh in m CM CO in CM On s- I vi- r-l ON <f rh c in CO r- <r CM CO s. vo» in <i- CO CM rh rh O O ON ON CO CO ce c s- I Is- I s - I s- no vo > vo UN un m UN <f i-h (\l CM CM C\l CNJ CM CNJ CM CM > CO c <j- r- p- cm CM CO CM (0 0-4 s- I CO no c rh 00 m r- en O UN O CM <t s- I UJ 0> CM r- vo r~> in c r-l r-l On c in in r» cm m CO s I - no s I - ON I s- ON ON r-l tn UN rh z CO O CO O vo no CM p-» CO CO vo I s- CO ON CO ON On UN m ON r-l CO cc Is- r-h CO, CO O in H <f in» in r-t O 00 If) O <t CO CO ON so <r CM O CO On O CNJ CO vo (\j rh O O rh <t CO CO On n CM s I - CM CO CO On UN s- -i I CO ON m i-h CC' no CO r-h m <r CO CM rh O O CO c r- p- r- so O UN UN <r <f CO CO CO CM CM r-i I. r-h.-1 CO CO CO CO CO CM CM CM CM CM CM CM CM CM CM CNJ CM CM CNJ CM CM CM CM C\j CM CM CNJ CM CM CM > rh c O in cm in n m rh s- s- I I m c UN ON CO UN <t m CM no UN <r CO <r CO UJ On <r m f c rh rh r- c <r c <j- s- I CM rh s- I r- cm s- I in UN r- <r CM CO O CM s: CO <r r- cm t-h c <r» rh p- m CM n r- r-i \D UN CM CO vo <t r- lt, 00 UN s- I CO CM t- O CM CM CM <f O vo > <t UN CO CM s- I UN <t <t UN no n <f CM Is- * vo CO UN vo p- c O CO CO c n vo CO ON m cm in UN CM ON no CO r- <r r CO - r-l CO <f t-i cm c r- v - m<t <f CO c c CM CM CM rh r-l r-l O O ON On CO c CO s- I I s- I s- - ft CO c c c c c c CO CO CO CO CO CO CO CO c c c CO c c CM CM CM CM CM CM CM CM CM > UJ r» c <f c ON O rh 4- c 4- <r 00 O On ON CO CO O ON CM un m s- I CO fn- UN UN <r O s <r vo O O c c in m vo ON ON no cm r- in <r- O- m ON On O O rh UN <r CM O r-h rh CM (MM> c c c vo CO s I - s 00 vo r- r- c CO I - ^ <r un CO cc <j r- vo On vo r- O O»0 ON CM P- O ON vo p» r-l <t ON Nf s- O I in CM s- vd vo <i- r» rh -3- r^ m p- c r- CM in c in CO CO CO ON UN O no cm CO UN CM I n c CO CM r-i rh O O ON ON ON CO CO s I - s I - vo vo in m <r <t <f CO CO CM CM CNJ r-i r-h r-h rh m in in in in in in -J- <t <r «* <!- -J" <r <r <t <r <f <r 4" <t <r <r <r <r <r <r vt in <t -a- ON CO c p- CO <t m c d- r- UN O CO m UN vo r-i t-i r-l CM UN p- vo r- UN > in CO CO CM c in r» cm p- On in \0 n UN rh <" UN CO vo UN io CO. no UN v0 no UJ <f cm cm p- I s- CO CO CO r-i CO On no s- O r-i ON I I s- CM s- I <t CM CC I vo UN 5: -a- m p- <M CO vo p- r- r- rh I s- CO O < rh CO CO vo CM CO CC CO <r CO CM CM C0 CM vo CM ON r-l CO 4- in UN m >j- in r- CM O rh n m ON vo cc 1 1 no i-h CO, CO in vo c p- r- \0 O p- p- P- Is- s- I r- Is - s- I r- 00 s - O r-i CO UN 00 r-i UN CO CM UN I s- ON CO c c c c c c c c c c c c c CO CO CO ON ON ON ON ON O O rh r-i r-i i-h > r-l vo «ON rh <T ON i i 1 vo c UN I s- CM rh ON CO O ON ON rh CO <t c CO CNJ Is- rh UJ r- CO O CM rh r~- <t <f OH^ CO ih <r vo 00 vo <f O un CN I s- 0> r- s- I s c c c CM vo CM c CO vo r- in -I- n no CM vo CM CO i-h rh CM CO <r CO CM <r H CM eg r-l O m c c CM P- <t ON tn rh O O O ON UN UN no c in r-l ON mo CNj CO vf m CO CO P- rh sj- \ in O vo cm n N0 CO in On r-i CO r-l CO CO CN CM C<N (NN CO no O' r- c CO CO c r- rh vo CM n in CM CO <T m s - CO <fr CM s- s I I - <t- vo no CO. O UN CM i-h c T> CO CO > O O rh r-l CM CO CO <r un in un vo no m 4- CO i-h On r~ NT CM CO no <t fl rh rh rh CM CM CM CM CM CM CM CNJ CM CM CM CM CM CM CM CM CM CM r-i t-i r-h r-h r-h 1 in m vo cm c m rh CO k0 J CMtH ON On 0-N -* CO UN CO CNJ NO r-i s- I CO O UJ X O rh rh CM CM CO c <r in m s- CO ON O rh OJ vf in no s- CC I r-h CO <t vo CO I 1/3 O rh rh rh rh r-i r-i r-i r-l r-i rh r-l rh rh r-l r-i CM CM CM CM CM CM CM CM CM r-i ON c 0N CO CO _J O O O O O O O O O O O O 3 UJ Q. X

74 67 > vo vt la CO en CO in O P- m *> -* CO CO CM * CO CO ON CO r- i-< c p- m CO O 00 c LU CO CM CO ON p- c r^ c r- rh vo rh On r-~ r~- <t- vf -JOOOO r- in 00 s: *3- O O On CO O n c m O vo r-< CM f^ On 00 ON <r i0 vo in c CO CO rh rh c rh -3" CO CO On vo uo m r- rh r- <t <t m > m O CO f> On On 00 CO CO CO CO ON rh CO vo O <-) in CO rh On f- LP, en r-i O CO v -d- c i-h On CO vo in - CO CM CM <-l r-t l-t l-l rh CM CO CO ON <f >r <t c CO CO CO CO CM CM CM CM CM CM r-l > vo vo On CNJ m i r-t CM <r CO O CM <r OOOvO CM r-< c in P- CO CM 0> rh CM On LU in rh O <T CO O vo CO CO CM rh rh v0 in c c CM * -t r-t On r-t i-l O O CO r-i 2 O P- c*> r- rh CM rh r- ON CO t-h <r CM f~- r-t r^ CM ON CO m c >$ m p~ CO CM CO -3- p- m rh m On CO ON 00 On CM e vo CO CM -I CO r-i mh ifl Hlfl xo rh CM vo 00 \D <t CM CO m CM O r- in c CM On CO 00 CO CO On O CM <f vo On r-t c in in -3" ON On O On CO CO c c p» Is - r^ r- r- vo vo vo vo CO O r- p- r» r P- 00 CO > rh 00 vo m On -S m - <r On <f CO s0 00 rh On rh CO C^ voo-j cm in v CM vo CO vo LU xo On i-h P- r*- r- P- r- c in >d" c CO CO 00 CO CO CO r- CO p» rh m cm in «O O <f vo Z NO CO 1^- On <f 0> rh in m CO CO CO vo 00 i-h CM rh C0 CO r-t CO CO T \0 r-t rh CO vo On c-h vo r t p- vo On ON CO cm m On CO P- vo <t 00 m c cm rh rh O ON m <f <\J On p- 3- m r~- > CM ^C <r CM v ) 0D On CO > P- CM -3" in vo CM \0 < m in in m in in in in m O «i*- r~ r- CO CO CO c p- > in <r cm 00 rh CM c\j <\j cm CM CM CM CM CM CM CM CM CM CM CM CM CM CM CM CM CM CM CM CM CM CM CM CM CM rh > LU * vfl MO cm p- <r CM On ON vo vo ON ON vj- m c CM CM -d" CM CM P- P~ On r-l vo vo in CO 2 vo lo \0 CO CM rh rh vo vo CM CO On r- m 00 <r On P- 00 CO CM vo vo ON ON c CO m i-h p- \t\ a tfi c -3- ON <} v > CM vo On <r ON CM O O O CO CO 00 f»- c, <3- vo On CVJ ON en tf O c ^0 in i-h \0 CO CM CO CO > c in in c c r* <P r- CO CM \0 en rh rh CM CO tfl vo uo ON «S- rh CM <t vo in cm CO vo On CO c On On rh rh CM CM c -3- m vo r- CO On O rh r- a- rh r CO On -d- O so CO ON p- in CO O 4 * <r <r <* <r " vl- <r m in m m -a- <*- <r <* CO CO CM CM CM rh i-t p- p- <j- vo CO rh <r On On r~- cm r- rh 00 vo CO rh p» Ovf H O >T CO p- m p- > c -3- c CO rh r-^ rh s0 CM On O CO ON CM CNJ CM CM <f CO f-l O On O m LU ON p- cm c in rh c v r- in r- r- CM c v c ON P- vo r-l rh 0> On rh P- i-t CM CM vo 2 m cm p- CO ^-t <j- m m m On <r CM CO O m cn CO 00 CM CM -3r -d- r- -3" CM rh m CM O r- CO - r- v O CM vo <r >t ifi vo <r On CO r-t P- vp M HO vo n 00 in On CM CO CO CM r-t O rh CM <r 00 CO On O <r CM - I r-l O O O i-h ft i I O CO r- in <t c CM -t i-h > xo l-t O rh O ON O r- <r h- CM CO CM <t r^ n rh r- P- CM O On vf CM r-t O LU 3" m p-.3- CO ON On ON -3" c n r- r- c in m r- CO <f CM 2 O On CO 0> v ) On CM CM CO r- r» r-( 0^ CO c in c r~ CO r~i O O O no rh 0> r-.. i CM m c r- CM CO CO m -a- cm i-i m p~ CO rh in <r in in CM CO CO >3r cm rh en in in 00 CM CO n CO CM r-t O O O O c CO CM rh rh 1 p~ p~ r- O r-t ^n m CO r-l t-t CM <f n <r cm rh cm in p- \D 00 CM On 00 m -3- LU X ON h c in p» CM in p» CO vo ON CM in > c r- r-t m O -3- On 4 in rh CO <r rh i/) CO <r *?( <r m in m m so vo vo vo r- r- r» C0 ON ON i-t CM CM CO CO Sr m _l -H O a Z) LU a x

75 68 > UJ 1-4 m O C7- r- <t > CO CT> cn > CM <r <T CO m p- CM \0 en <f O r-h en en r- r~ <f n vo CO» cn in vo m in O r-( CM 1-4 CC 00 vo r- O On On fm H en vo r» m en <t r- en CM in cn r- in cm CM m 1 <r 2: -I On <r e\j en j- in cm vo fm CM CO in 00 en r- CO en <t r- CO r- en CO cn c fm <r ih CM1 CO c CM X CM -O CO O CO in ON CO in cm CM 1-i If, <.- r-i O O O O O CM i-h l-( i-h i-h -i r-l CM fm 1 «H ih CO r<- vo m i-i O O O > r- <r CM v ) 1O r- CM CM r-h CO r-i r i en O <r r-h 000 UJ r- r en en 1-1 c CM en CM p* O vo fm r-h CC r-h 000 2: p- m O vo O f- r- H ih O r- en 000 r- cm en <J- r-i en O CM <t CO r- f» CM m en in O O. ( <t CM en r- m fm no en 1-1 r> vo in en CM r-l O O O O O 000 O O O - r-i r-i r-i > LU <n en en in vd On r-h CO LP, 00 m en r-h O 000 s CM. cm no i i c <r <r <s- O tf\ r-h CO 000 en H fm <r CM i-h r- CO ^0 CM O O 000 NO [» r» O CO <r i-h <t r-h 000 <f in in CJN <r e\j <-i O O 00a «f\i 1 1 O O O O O O O O 000 O O O cm O O en <-H O 000 > m en O 000 LU cm 000 O SI O O c c O 000 vo O c O O O O O O O O O O 000 O O,-5 > ^ 3 LU O O O O in O 000 cn O O O O O O *~\ O O O O O 000 O O en t- in 00 m in CO r-i C7n CM O <r <r CM r-h r- r-i CM t t <j\ m r O CM CO in»d- vo LU X CO en e\i 0> c CO On ON H en n CO CM vo r-h vo en O CO r- CO r-i <r On m CM CO m vo!» CO f> O 1 1 CM en m O P- CO O r-h 0-1 <r CO 1-1 cn in r- CM <t r- O _l 1 i-h i-i 1-1 i-h 1-1 f\j CM CM em f\i CM CM CM 01 en en en cn en cn <r <r <r <t m m m in no D LU CL X

76 69 > UJ 1-1 n0 0> vo p- p- CO <7 O CO CM O ON ON ON m CO CO r- CM CO CO r-i i i CO ^O UN p" cm O c <p r-l CO CO UN i i v0 CO O i l r^ P- CM p- rh} CO <r s: <r H m p- CM -I c in CM vo CO CO, m CO ON CN O CM CO, rh <r c UN OJ CO p- CO CO CO O CNJ m in CM CO c CO r-i r CO. in ON CO r- O CO c <r 4" rh P* rh CM <r CM C- r- r- P- CO O CNJ u r~ CO ON ON > O O 1 1. O CO r CO r, O p- «ITS CO N H O ON c P- in <p 4" CO r-i CN r; P- P- vo in <r CO. CO CNJ CM Oj f-h CM CM OJ C\i CM CNJ > CO CO CO *0 CO 0* CM cm p- O r-l CM O t UN i i CM ON 'UN ON P- CO >r CO in UJ CO in rh CO CC ON vo O vo O i0 m r~ CM CO UN P- so r- UN UN r~ CO i-h <r 00 z rh tq «-) i CO CO in c CM <r 00 O r-i UN i l r- <M r- UN r-h <r i O ON in vo m O m CO»H CNJ CM CO <r CO O vi- CO <0 O r-i vo CO, rh r~< CO i-h p- CO CO P» CO P- CM m CC -< <t vo CD CO CO vo 01 CO r- CC m CM rh CM <r 4- CO r- * en r-l CO SO 4 CO r-i ON r» UN CO 1 1 CJN r- <r CM ON p- NO UN <r CO CM CM CM i r-h r-h r-h <t * <T <r r CO CO, CO CO CM CM CM CM CM > CO p- CO r CO, On r~ vo CO <* in CM m CM ON O CM <r P- CO CM m <P rh UN vo UJ p- C*l CO cc CO 4 r- <-i CO \0 O O p- CM ON O CO CO UN <r m z m r-h P» s0 p» CM CO ^ N vo CM m <T" \0 r-l P- c 0" UN ^ CM m CN r-\ CO O 00 UN n CM in cm r- O p- CO P- <r <) CM CM <r O <r ON CM CM UN P- CM CM ON p- eg i-h 1 <r CO CO m P- >t CI so ON ^J CO *a P- r-h CO p- r > <r m r-4 P- c\ r«- 41 CM O r- UN <r 4 CO ON cn CM CM CM CM CM CM v > m UN <r <r >r CO CO CM (M CM rh r-l r-l i l I p" UN w0 CO CM P- ON O P- UN <T CO CM rh > r-l CM CO CO p- p- m Osi CO H CN vo 4 so 1 1 CO < <r CO O CN G, c CN <r c LU CM O 4 p* CO P- CO CO 0^ P- m <r ON rh ON ON CM ON r~ <r CM CN ON UN rh ON s: P- m CO <r P- CO m <M imi <r UN CO UN UN io <r O P» CN CO vo P" O r-h 4 4 vo CO ^-i O p- CM CO CO r-h CO rh O * <r O H c m <r CN r-i ON rh r-h r~- O CO O p» r-i en rh O I'M OO O m 4 r» CO 1 CM m C^ <r CN p- 4 CM rh CN CO P» vo r-h p- <r m m ^i r^ CO ON vo - CM 0* CO p- s0 UN UN m 4 <r <r <r CO en r CO vo m UN <r <r <r CO CO CM CM > n 00 CO r-t CO r- in. p" 1 > r-l «0 O UN CNJ CN > rh O ON m CJN vo 4 CM LU vo CM p ON l-l <r rh s0 P- m CO ON rh i-h CO UN ON p- CO rh CO CO 1 CO p- CM CO <r vo CM ON -- CM en < l CO CO CM P- m CN ON r-i p- CM CM CD CO CO O H CNJ m i-i r- cm r-( CO <r p- UN <Ti O vo r-i ON CO 4 CO CM <r CN UN CO CM c vo 4 CO, p» CO CO r-\ r vo 00 m UN ON O UN P" r-i m 1 CO UN r f-h CN p- O UN 4- CO ON CM O CNJ CO <r p- c p- ^N CO rh On CO CO p- p» vo - > vo \Q UN UN UN UN UN in CO m 4 <r <r r c CO CM CM CM vo <r CM m <c vo P- m p- r- 0N 0> ON 00 r P- O b CM CO ON CO <r ON i-i m CO, ON CN CM > ON vo CNJ 0> CM O O CM CM c i-h <T. P- UN n CM vo O CM P- CO O O r CM LU <t CO Ift CM CO i-l m i r-i CO cc p- CM 3 m P- UN CO a» UN CO CO P» 4 CO vo O 00 s CM CO in io CO <r <f CO r~ UN r-, UN <r UN un cn P- UN UN CO CM < rh a <r p- ON UN r- O CM i-h p» CO <i- <r P- CO CM CO UN &N <r O p- <T CM CO p- UN <r CNJ r-i ON p- m c O CO CO CO 0> un CM O 00 O UN <r CO CM r-l rh i-l O CN ON On r>> ON CO CD c On C\J itv <r r CO CNJ CM CM t- UN O m < CNJ c in f-i CO «a 4- CM i l ON CN On O rh ON UN CO CM rh p" CO LUX O rh r-h CM CM CO c >r uo in O r~ CO ON 1-1 CM <r UN O P<- CO r t CO <r -O CO i/>0 f-t f r H i i-( r-l r-\ >-i ih n r-l r-l r-l rh CM CM CM CM CM CM CM CM CM CO CO CO CO CO CO _J«- O O O O r> b a O O a O O DLU < O-X

77 70 > LU OHOOiTiCOHiaHHFKMMOlfltMvOdOvOMin C^OOC\lf\ Of^G>fHvOOrHvOOr-lvOi-Hir\r-II v--4" r~c^vocc^r~\0<j-<ftarvrr>c^i(\ivcrcnrihi^-c^mccn\0>d <M<7>\0'-ivDiAc\j - r-<rm<j-vc<i-(\j ninlrtoon>0(mo r-voin<t(*l(mhhh > ^^inccvr-<fc\ic\jovovor-<-c^voir><mcnjas>ruj vr^i^on\c\]r-<\jr-<-icrh<f^i(\jfc\i(\ir*-i^-rh<f«0{\i 5; if\cf^c^i\ir-cnnocmn(\ic<ij-vchir\(fir,-hi<-vonf(m<fi-i( cx5(\i>cx30fr--<r( v -c)r v -^c<>cnvootnrncr»in>-hi -cn'-i s \OLf>irv\Ovr~>Oi-ic>d-trivOh-<X)r-vOtA«i-(\jrHOcr-vOtr\ i^i^ 1M«Hi^ 1H^<\J(\J<NOvj(\JC»JC\J(\JC\J(\irvJf\J(NI<\lf\l(\J(\J(\Jf\J'-ti-<'--<rH > rdcvocrr\i^-<)-fmacn\novdc\jr~ors-d-^homsjfmvoono lu (>Hinv^tMa)inHvinHvOin[ -pn(oh(>^voinjo( (>rm 2, <\-d, inin^vo<- (\j^vfsf rg<fr^in'h^^r-c<^c>ini-hr--rvocn>-icr>r <,iirir-r--r~-vovr~r-<c(7vcc\jr^\oc(>incn v -ir\c^<njcr»(^-if%<\i <nj H>(MM»c(DM^vO>>Oinir\ir\4-<r-TMmMnn^NNi\i (VJCsJtNJCNJ^i^r^rHi-HrHi-lr-lrHr-li-lrHf-li-li-li-li-Hi-lt-lt-li-lrHrHt-ti-if-t IH 00 > LU (D>0(NOONO^M^aciAvOOvONOinHinMnHMvOM<iir\vOc vooirvr^<j-«3-inv >c<"ir--voir\ir\ir\ (MONC\i>-(r-vc ric^r-iv-r-cr^^in<trfmr-i^<>r,»f,-voirvir»-d'-^ fo(nac\ji-trhc>ci v vr-r-in<t-c\j!-ic\jr~mno'-tc Lncr^-<-HLn!Dr^<Mi*- -r--vo CnrnC^C^fO(^r^C\iC\J<\J<NJ<\J(NOsJC\J(\J(NC\JOsJ(\J(\JC\Jf\Ji^rHi^i-li--li--tr-l in > O\c0'-ivj-<\ji-tr--m lu <t<m>inmcincitovj- 5: 0<j-c>f-3-<\iinint-ir-dv (NjiHrHOONcr-vOinvf (fi-tnonciniatohoj'hinin^ ciovo<>ohmevon(iiiflhinhhnffi <i-mf-c\jcy>\i^voiri\0.-<mr*-<"i cc\icnmr--«-)cm[^-\c\iinc<\jr^-<\i cr\i<mi-icar-r^-vin<i-fof\ii-ii-i r > LU 00 ^^vir^iacniinv-^inrr^r-ir-ion^i^-c^d-ontnf-s-on-d-tnj <fo'-<i^-cincncn(<, ir^'-<c^>-to'-ion-d-fri<f<njri v -r--r-ir> -S--i-^f-i<rvOLam( v-c>iat>-fof-irhi> --<t(m-d-c^cmcn<j- ^(MOvO^gOcr-tn-a-rOt-ii^-r-xOirifsjr^fMr-iNc r~r^r--h-r--\ovoosovovovoir\inir>iniriininir\ir\intnin^-^- fm LU I _l -1 DLU a. x ^r-i^-c^<-iininf<-hi-i(\j<j-av<j-c\j<-<viini^-voc\i\in<j^r-icninp-<mif>r,~cn*c\jin>cr>r*-«hin<i-on-d-ir>f-t^t-i cri>d"-^"-d"'d miair\in\ovovovoi -^i - s -(^c^i-hfm<mc,ic>3-in OOOOOOOOOOOOOO 000<->OOi-HtHt-HrHr-lr-li-<i-li-li-l

78 71 > cmoin4-incmr-rhocmcmo«d" tocl-jitiooto-d' >i- <j- m cr> in m rh LU mmnoinh vf r-- \0 «h vo COH<f<TvO<flf»H m a> en in t-< r- CO s incmvorhrhinm <t in m m rt r- v > <f m i-i in t-i i m CO rhcn-d-cmr--cnr--r-«d-cc> vovohj'^inn c in cm cm» vo (-thht\jm<r<j-ininir\invf<fn rh>cr-r r~ >00 < 1T\ m m -d- d- t-i > rncmr p-vcn-d-cnxcmcncinr-cm cm m J- en c in 4- lu cncncncmrh<i- \inin-3"incncn i-ll^voh\oh<fod, CO CM CM vq t-i vo en m 2 invocnr^r-cmo^cmomv envocmcnr <COnO r-l M O M en f-i O!* rh >3- v en in h mc h cr^mojin^mm <r <- cn en CM i-h 0* 00 ccsjvjrhoooooo''f>cr--r ^ in in -d - -d" vf vf <f < -3- «r <r cn en O rh rh > IflfflOJMONHtO'JCOsfHHH Ov000rl00Hl>-C0 H04 CO N LU invovencninc\0<fr--inr- H<t OfflvOOlfl CO cm <! vo cn 4" CM vo p- S voomm^hhnhminco-jo^ sooosr-oi-< s- I d-!* p- f^r»<fn'-' rthh 'H OK)if\(NJ(10 in(moocer-> <r en t-i sd -4- r-i CM cccc c c c r- r- r- r- rh c > O ^ W ff>c0 if\ O H ffi ia»oh C> Hr-vO-JCOlTHOrH <p <f en rh >d" en f LU WinMO^I^O^sfOMNO^MvO en <h in m \D CM CM <d" -d" vo <f O r- S incmoinr^r-cnminrhorhc rt O* JHH ifl^ rt CM s I - CO t-i cn CM en vrinrhr-rmcincmoocr-in -3-.-IO\r-lACriCMrH O vo en t-i CM r- \OvOincn4-<j-cncncnencMCMCMCM CiJ.MrtiHHHrtH > r-<frhinrhinr r-vorhv f>'-h>-to'-<'-ir- ^ CM CM r- c CM vo LU -d-eninr-r~cm«d-cn rhoin^r-r-rh i-h O CM O CM s cr-soof-inrhincmc^ cioh^^((in d- p~ r- r-i en c^. CM r-<j-i >-<rrhcinrhr-<i-oven h ^ONtnw c v > <r <r ia CO CM vo ccar r-r--vovovoinin in<f«d"inmininvo vo in in in m m in O (MCm<mcmcmcmcmcmcmcmcmcmcmcm CMCMCMCMCMCMCMCM CM CM CM CM CM CM CM CM en <j-r~incncncrhcmcn ^mn<rhr--j in cm \0 <T cm t> * > l^cinr-favohmtn^-r (\J(\vOO>OmcOCO i-i en en vq Q\ If) CM LU C7NO > 'Oci N-^i-icni*-r^cA cnene\jcm-d- inen<r cm \D en en en CM m s: O >0 ^ O r*- CM P- en 00 in CM r-mm en-d-invr-ccin c in c r- O CO m in i~-r»-r*-r N0vOir\ir\«3-<j->f-4-<t-«d - <r<r<-<r<r<r^--a- cn cm c vo <r en CM CM 4- -a- <r >d- <f >a- *vt-*-*<r<r-s--* 4--d-«d-<t-d-<J--d-<i- <i- <r <j- en en cn cn en 1 infloinin(>a>h^noj-<t OC\Ji-nr~i-«c\]r-iCN in ^-1 «0 cm in <r vo LU X encmooccc^^rhcninc (MvOHvOPlOcOiO vomxjh vj- > in CM I/) O invr-^rhcmcninvr-c OHM<fvOOO>H en m p- CM >f p- _J rhrhrhrhrhrhcmcmcmcmcmcmcmcm mcim^mmm-t >d- -d- -d- in m in u"\ DLU a x

79 72 > c <t M(>ONir><finH cfmor~-i-i >f cm v c\j v > <x> h > w Ui nin(\ii-ifmvor-<-hoi-ir-c\ic\ic\jr^r-<\j <tmmr-*<rvoin s r-,-i<\ir»<mcc\jr~--3- in<ti v-rhvof-)r-ln<rrnfvjrr->h'-tvoovo >3. fr) sji-i^hoin<-i\oc<, i--ic7>cr-r~-h-r--r-i v-r-r-^-vminin <f t-l > <r!vov^cr^cohh<finccnjvocmoincincinin>j-vo<-icrc> l±j in<fr^oinc\jccnrovovoc\jvoc\jcjci^rminvjir\rnvoc\jcc^-* 2 h-onic-j(mf-fmr-^cix\mvoni>voort(«ic><r r^vovin<f<f<r<f^t<f-*<f<j-<r^f rirr > csj (NJ' _ c>^cr~vovoinno (^mwmmmwmdmmn^mmmmmmcirmnntmfxjnnmn c, > c\iinc\jr--3- r-vovoc<fr>fri^r-c<\c<\i<r(\j ill in<t<rr^<fcr\jfsilr»^0'-<r-<rhr~c>co'-icvo>s-cc>-*<j-r--d- S 0"3-r-r-vr-iAmr\j>r<-i^-icnvOvOrHir\c>cencA<^csj'-<-*vOO CDvO<rrNJOCr^vOinc^^rHf-Hf-ii-Hr-(r\i(\i(\ifsi>-ii-i<\jrNji-i vovo^ovovoininirvir\inininiaintr\iniainiriir\inininininiaininir\ir» <\J r-i > H^c>HOc>c>r-int^vOr-irc<Ni-d-iAvOt\jr-iAvOvOinc>^-c>(\i UJ <fcr^it\cr\i^c<>si^r~rhr~tn<f<\jh^r^cmo"i<r<foc^r ri-a-f-i 5: ^u^c«a-c>^iacinincnvi<rr^r~-c>voono<rr\jcncf\jcoi-i >j-iav )vovo-j-fnjor-ia <i-mvcc\im c\jc\jc\jiaoc<-r-c'-ho r- OOOOOO OOOOOOOOOOOO<-<OO0NC0C0^-m(NJ 000 > 0\<fO^NH(\J>0(MvOvOCO>OMiiMnOOHOOOOOOOOOOO LLl tnc7nvj-r---ir-<rrmrniricx3f\jr-c\jiat\j 2 r-tmr--r-<\irhi^ovocnccnj in^-3-vmr\jcrvoinc^i vo vovovolasa-cnfvjoocmhvofooooooooooooooooo fm(njf\j(\jt\ifmtm<\jh^lhr-toooooooooooooooooo CO r~ca-v^>rir\mc\j > <j-inr-cc\j<i-ccvovoc UJ <t-,_ ) 0<-lC\l^-vO<fvOfViOOOOOOOOOOOOOOOOOOOO JC cr-<>r-i<rr-'-< r-ion<ro^hvo(nooooooooooooooooooooooo 00 mrm^if-l^hooooooooooooooooooooooooo rg h r^c<fvocr\a>«-tir>c\imc<r <r*^vocmn(<m f>c>c LU I rhor-i-4-c<t'-<'-<t\jlnr^voc\jcirvr-*r-min^- t mvocmnjinmnhifi^^^inrtcnfhc^mhocmccv sooof^r^i^<»<»^c>oh(njfnj<c-d-iryif\^p~<>c><-ir\j<*> _l Z> LU CL X

80 > >* r- <T O in r- r- CO.-1 CM 0» O m 00 O CO 3 r-h O CM r-i 000 LU O cm c O vo <r CM CO P«- 00 en * -O O s: c c U> vo f-h CM <~< c in O N ON en c> en O rh en en O O rh 000 in m m L.O in d- «* -d- <r <r in <r <r m <r <r <r CO CM r-h r>- r-h 003 <t O O O O O O O 3 a O O i-i > vo r- r- en (JN O.-! IT\ CO <r CO r-l in <f O <r r- <r c m c CO rh O r-h f-h 3 O 000 2: m en r~ r-l <}" \ c e^ CM r-1 <r m O itv 3 vo r- vo m in L-O <r fh <r <r 000 CM CM CNJ tn CM CM CM CM CM CM CM CM r-l O O O O O O 3 O O O O O O > vo O c r-l CO CO r-l 3 c c 000 LU 00 < l <r O in CO vo O <3> O c: r-( LH CM O O C O 3 c r- in O vf r-t 3 c 3 OOO CM d- <r <f c cnj O 3 O 3 H O O O O O c 3 O O O O O O O OOO 00 > <r 3 3 O O O O 3 3 O 3 OOO UJ 3 'J -J O O O 3 S O 3 3 O 3 OOO 3 3 O O O OOO r- O O 3 3 O O O O Q OOO» m O O O O O O O O OOO > G O 3 O OOO LU 3 OOO 2 3 OOO c O 3 OOO vo O O O O O 3 O O O O OOO ON CO O O O O O O c Q O O O OOO 000 O O O O OOO > OOO LU O O O 21 3 OOO O 3 OOO O O 3 O O O O O O O c OOO CO r- CM en O r-l <r * vo 3 m CO <" 3 en O vo H X en O h- CNJ r- - 1 u^ in r- 00 -a-» > CO CO LU l/) O _J 3 r-1 CM t 1 O c. CO GO 3 O r-l 1-1 i i <r.* en m 00 \0 CO O O uo <r vj" r <r O CM O CM 3 3 cn O in r- c CO <r m CO r-l <f 3 <r O CM m en rtom r^ 00 3 tf r~- I*- rh in m «Z> LU a. x CM CM cm CM c c c c c CO <J- <f <f <r m in in m vo vjd O r- r- r

81 74 APPENDIX B Descriptin and Explanatin f the IBM-1410 Cmputer Prgram Used fr Calculatin f the Respnse Functins This cmputer cde was written t cnvert the respnse functins as given in Appendix A frm "Cbalt" pulse height units t channel pulse height units. A sub-prgram, INTERP, available frm the KSU Cmputing Center, was used t interplate between the given pulse height units fr the desired respnse. The input and utput parameters required fr the executin f this prgram are given in Table B-I. Table B-I Input and Output Parameters Required fr Executin f CONVERT TIME Nrmalizatin factr in first clumn f each respnse utput COBALT Channel where cmptn edge frm Cbalt-60 falls IMAXTP Number f pulse height unit values in data NPTSTP Number f pints that INTERP will iterate n t fit a plynmial XABCIS Pulse height unit values as given in Appendix A FORDIN Prbability f event per light unit as given in Appendix A TVX Calculated pulse height unit values in channel units TVF Calculated prbability f event per channel Executin time fr this cde varied frm apprximately 30 minutes

82 75 fr 1 Cbalt channel 20 t apprximately 55 minutes fr 1 cbalt - channel 200. Output frm this cde was in printed and punched frm, 5E14.8 frmat. The punched utput was used directly in the unflding cde.

83 > 76 Start: Read in prgram wand cnstants Read: data l Set: L=l RUM-1 (y^)«- _SZ_ Calculate TVX Call INTERP Calculate TVF ^esv IS stvf>0 n Set: TVF=0. L=2 _Li Set: L-2 RUM=RUMH ->(nj END Output: TIME, TVF Figure 25. Lgic diagram fr prgram used t calculate the respnse functins

84 /* ) 77 6 THIS CASE ) c THIS PROGRAM CALCULATES THE RESPONSE MATRIX FOR 1 COBALT IN ANY c CHANNEL c DIMENSION XABCIS(200)»FCRDIN(200)»SUM(200)»TVX(200).TVF(200) 1 FCRMAT(3I5) 2 FORMATdH.5E14.8) 4 FCRMAT(5E14.8) 5 FCRMAT(F5,1) 6 FCRMATU0F8.4) 7 FORMATC5E1+.8) c c MAIN PROGRAM TC CALL INTERP SUBROUTINE c c TVX = PHU VALUES c TVF = PROBIBILITY PER LIGHT UNIT c XABCIS = PHU FED IN AS DATA c FORDIN = PROBIBILITY VALUES FED IN ITERATION POINTS AS DATA IN c NPTSTP c IMAXTP = = NUMBER OF NUMBER OF PHU VALUES IN ( DATA c TIME = NORMILIZATION c COBALT = FACTOR CHANNEL WHERE DESIRED COMPTON EDGE IN FIRST FROM COLUMN COBALT OF FALLS EACH ENERGY c 8 READ<1*5)TIME READ <1»5) COBALT READ(1»1) IMAXTP. NPTSTP READ (1*6) ( XABCIS ( I) * 1 = 1* IMAXTP) 50 READ (1*4) ( FORDIN ( I),1=1* IMAXTP) L = l RUM=1. DC 300 1=1*200 SUM (I )=RUM TVX( I )=SUM( I )/COBALT GO T0(10,275) *L 10 IF(TVX(I).GT.0.01DG0 TO 200 j=l+l TVF( I)=( { (FCRDIN(J)-FCRDIN( I) )/( XABCI S (J -XABCIS ) ( I) ) )*(TVXU )- CXABCIS(I) ) )+FORDIN( I GO TC 250 CALL INTERP( 200 IMAXTP»XABCIS*FORDIN*NPTSTP *TVX *TVF, I ) 250 TVF( I)=TVF( D/COBALT IF(TVF( I).GT.C. )G0 TO TVF(I)=0. L = RUM=RUM+1. WRITE(3»2)TIME»(TVF( I)*I=1*200) WRITE(2.7)TIME»(TVF( I)*I=1»200) GO TO 50 END

85 TCC 1 78 i SUBRCUTINE INTERPt IMAXTP,;<ABCIS,FCRDIN,NPTSTP, TVX,TVF,I) DIMENSICN XN( 150) *FN( 150),FCRDIN(200),XABCIS(200),TVX(200)» TVF(2 C) 800 IF( IMAXTP-1) 810,820, TVF(I)=0. GC TC TVF( )=FCRDIN< 1) GC TC 1000 C THESE CRDERS TAKE CARE CF ECCENTRICALLY SHCRT LISTS 830 IF(NPTSTP-IMAXTP)850»840»; NPTSTP=IMAXTP-1 C CRDER CF INTERPCLATICN IS DECREASED IF LIST IS SHCRT 850 XCTP=1.E90 DC 890 INTP=1»IMAXTP \TP=TVX( I )-XABCIS( INTP) IF(ATP>860,870, ATP=-ATP 870 IF (ATP-XCTP 1880,890, ITP=INTP XCTP=ATP 890 CCNTINUE C THIS LCCP SELECTS THE VALUE CF XABCIS CLCSEST TC TVX IF ( IMAXTP-ITP-1)392»892, IF( ITP-D892, 892, IF(ABS(TVX( I) -XABCIS < ITP +1) )-ABS(TVX(I )-XABCIS(ITP-l) :,892 ;1, INNTP=1 GC TC INNTP = NPTSTP=NPTSTP+1 C THESE CRDERS DETERMINE CN WHICH SIDE CF TVX IS DC 970 INTP=1,NPTSTP XN( INTP)=XABCIS(ITP) FN( INTP)=FCRDIN(ITP) IF( INNTP)900, 900, IQTP=ITP-INTP GC TC IQTP=ITP+INTP 920 IF( IMAXTP-IQTP)930,940, ITP=ITP-1 GC TC IF( IQTP)950,950, ITP=ITP+1 GC TC ITP=IQTP INNTP=-INNTP 970 CCNTINUE C THIS LCCP CRDERS THE INTERPCLATICN PCINTS C FCR INCREASING DISTANCES FRCM TVX NPTSTP=NPTSTP-1

86 TVF( I )=0. FACT=1. DC 990 JNTP=1»NPTSTP TVF( )=TVF( I )+FACT*FN(l) DC 980 INTP=JNTP*NPTSTP IQTP=INTP-JNTP+1 98 FN(IQTP)=(FN( IQTP+1 ) -FN ( IQTP ) ) / (XN ( INTP+1 J-XN ( IQTP) 990 FACT=FACT*(TVX( I )-XN(JNTP) C THIS IS THE MAIN LCCP FCR CALCULATING THE DIVIDED DIFFERENCES 1000 RETURN END 79

87 80 APPENDIX C Explanatin f the Input Rutines fr the IBM-1410 Unflding Cde Being Develped in the KSU Department f Nuclear Engineering The unflding cde used fr this wrk was written by Eckhff and Hill (8), KSU Nuclear Engineering staff members, t unfld cmplex spectra in the least squares sense, and t slve fr errrs in the unflded spectra which result frm statistical errrs in the cmplex spectra. Presently under further develpment, the cde cntains several ptins especially designed fr gamma-ray spectrum unflding; these ptins were nt used fr the neutrn spectra unflding here and will nt be explained. Executin time fr this prgram varied frm apprximately 20 minutes t 45 minutes, depending n the number f mnenergetic spectra and the nature f a particular slutin. Output was in bth printed and punched frm. The input rutines used fr this wrk are given in Table C-I.

88 81 Table C-I Input Rutines fr KSU Department f Nuclear Engineering Unflding Cde Card r Deck iclumns Infrmatin Card 1: 1-3 Number f channels 4-6 Number f mnenergetic spectra read in weighting factrs 2 weighting factrs f unity 3 weighting factrs f 1/ calculated spectra are printed calculated spectra are nt printed Lwer channel limit f least squares fit Upper channel limit f least squares fit ne iteratin n beta vectr spectra read in n 8F10.0 Frmat spectra read in n 5E14.8 Frmat calculate standard deviatin fr spectra standard deviatin nt calculated Card 2: 1-80 Any identificatin desired Cmplex spectra deck: 5E14.8 r 8F10.0 Frmat 1st number is cunting time Weighting factrs: Usually nt read in (see Card 1, Cls 7-9) Identificatin f cmplex spectra: Cnsecutive numbers t identify cmplex spectrum (1513 Frmat) Mnenergetic spectra: 5E14.8 r 8F10.0 Frmat 1st number f each energy 1.0

89 82 APPENDIX D Letter Received frm Oak Ridge Natinal Labratry Regarding KSU Data Analysis The fllwing letter was received frm ORNL in reply t a KSU letter which submitted a P-Be pulse height spectrum. Much prgress has been made since then in lwering the Frte circuit cut-ff pint; t date this cut-ff pint is apprximately 0.15 cbalts fr the KSU system.

90 " Oak Ridge Natinal Labratry OPERATED BY UNION CARBIDE CORPORATION NUCLEAR DIVISION 83 POST OFFICE BOX X OAK RIDGE, TENNESSEE May 5, 1966 Mr. Kenneth E. Habiger Department f Nuclear Engineering Kansas State University Manhattan, Kansas Dear Mr. Habiger: I am srry that we have taken s lng t reply t yur letter which submitted a P-Be pulse-height spectrum and a stack f punched cards, but we have been ttally ccupied with a rather vital series f experiments relating t the prper analysis f ur wn ME -213 data. We began lking at yur spectrum by pltting the data and cmparing it with ur mst recent P-Be calibratin run. We immediately bserve that althugh we are in mre r less rugh agreement ver the lw-gain "bite, ur curves d nt match at all in the high-gain segment. The truble seems t lie in the peratin f yur Frte circuit, which appears t be cutting ff cunts at 0.5 cbalts r even higher. The result f this is that very little useful infrmatin is btained frm yur high -gain run. Fr cmparisn, the enclsed plt shws that we d nt experience Frte turnver until arund cbalts. (Our data is shwn in clred pencil, yurs in black.) Since ur FERDO analysis f pulse-height curves similar t that shwn (as ur data) has resulted in unflded P-Be spectra which agree in mst details with the mre r less accepted spectrum f Whitmre and Baker [Phys. Rev. 78, 799 (1950)] we feel that sme srt f sajnilar pulse-height results will be necessary befre any attempt is made t use the FERDO cde. Accrdingly, I will await further wrd frm yu befre making any attempt t prcess the data. Althugh we can ffer n immediate suggestins cncerning the prblem, the disparity in the appearances f yur high-gain and lw-gain 6 C data

91 84 Mr. Kenneth E. Habiger -2- May 5, 1966 at the lw-energy end is smewhat upsetting. We d nt expect t see this, but rather curves which are basically the same. Further study is indicated here.»ry trulx yurs, End. RMF:vg cc: C. E. Cliffrd W. R. Kimel (KSU) V. V. Verbinski R. M. Freestne, Jr. Neutrn Physics Divisin

92 "» 9 1 <^/-//3 /wise c- A-J&

93 86 APPENDIX E Mdificatins in the B. J. Electrnics A8 Amplifier

94 ' f I ' - - ' I I Mr 4 rft-h 1 +** * f- -*/v 8**1!?l & >-* i»j*i *» 55 2j I> ^> ^ jllvc-i-w i w iwwxw *!«i) ILL 151 M

95 THE MEASUREMENT OF THE FAST NEUTRON FLUX AT THE FAST BEAM PORT OF THE KSU TRIGA MARK II REACTOR by Kenneth Edward Habiger B. S., Kansas State University, 1964 AN ABSTRACT OF A MASTER'S THESIS Submitted in partial fulfillment f the requirements fr the degree MASTER OF SCIENCE Department f Nuclear Engineering KANSAS STATE UNIVERSITY Manhattan, Kansas 1966

96 A3STRACT A study was made f the perating characteristics and parameters f an NE-213 fast neutrn spectrmeter system, capable f discriminating against gamma-rays; the system was then applied t the measurement f the fast neutrn spectra f P-Be neutrns and reactr neutrns at the fast beam prt f the KSU TRIGA Mark II reactr. The gamma-ray discriminating circuit ("Frte circuit") was adjusted in cnjunctin with the baseline setting n a linear amplifier t maintain a 1000:1 gamma-ray rejectin rati and detect neutrns f the lwest pssible energy. Phtmultiplier tube vltages f 2300 vlts r less were lw enugh t prevent phttube saturatin frm 14 Mev neutrns. P-Be and reactr neutrn cmplex spectra were recrded with a multichannel analyzer at tw linear amplifier gains. The lw gain cmplex spectra were characterized by a "peaking" effect in the higher channels due t high energy gamma leakage when perating the system under certain cnditins. The peaking effect was smthed using spectra recrded when peaking did nt' ccur. The lw gain cmplex spectra were successfully unflded in the 1.5 t 14 Mev neutrn energy range using a cde being develped in the KSU Department f Nuclear Engineering. High gain unflding attempts were unsuccessful due t the prbable difference in reslutin between the KSU NE-213 system and the reslutin characteristic f the unflding cde respnse functin data. Reslutin fr the system can be imprved by replacing the white

97 reflectr paint n the scintillatr bttle with aluminum fil. In additin, respnse f the system t mnenergetic neutrns shuld be measured t determine the reliability f the unflding cde respnse functin data.