- Email: [email protected]
High energy photonuclear reactions in 141Pr
Internatmnal Journal of Apphed Radiation and Isotopes, 1972, Vol, 23, pp 153-156 Pergamon Press Printed in Northern Ireland
High Energy Photonuclear Reactions in 'lPr EL-HUSSIENY M DIEFALLAH Department of Chemistry, Assmt Umverstty, Assmt, Egypt Arab Republic
(Recewed 10 May 1971, m rewsedform 1 September 1971) Htgh energy photonuclear reactions m 141Pr were studied makmg use of the method of residual activity and gamma ray scintillation spectroscopy techniques The yield values of a4°Nd produced m irradiations of praseodymium oxide target were determined with bremsstrahlung of maximum energy varying from 100 to 300 MeV The observed 14°Nd ymlds mdmate that there ~s significant contribution from secondary proton reactions LES REACTIONS P H O T O N U C L E A I R E S DE HALITE ENERGIE DANS LE 141pr O n a dtudld les r6actlons photonucldalres de haute dnergxe dins le m P r , en utlhsant la mdthode d'actlvltd rdslduelle et les techniques de spectroscopm de scintillation aux rayons gamma. Les valeurs de rendement du xa°Nd prodult au eours des lrradmtlons d'une cxble d'oxyde de prasdodymtum ont dtd ddtermlndes avec des bremsstrahlung d'dnergm maximum qul vanalt de I00 h 300 MeV. Les rendements de la°Nd observ6s mdlquent qu'd y a une contribution sxgnlfiante des r6achons protomques secondalres (I)OTOYI~EPHLIE PEAHIIHH BbICOHO17I DHEPFHH B 14Ipr I48yqenr~ ~owog~eprtbie p e a ~ H B~COROfl~Heprn~ B 14tpr, genoaBay~ MeTO~ocTaTOqH0fi aHTHBHOCTH H CI~HHTHJIJIHI~HOHHhIe veXHnl~rl raMMa-cllei~wpocHon~t~t Onpe~eaeHbi 8Haqenn~ BHxoAa 14°Nd, noJiyqeHH~Ie B o 6 2 I y q e a n f l x Mtlmen~t OKrlCH n p a s e o a n M n U c TopMoaHMM HaJiyqeHHeM MaHC~IMa~bH0i~ 3HeprH~l B npeaeaax OT 100 ~0 300 MaB. Ha6~IOAeHHMe BI~IXO~M14°Nd noga3~tBamT Ha 8HaqiITeJii~ni)ii~ BHJIaA OT peami~Iil BTopHqHMX IIpOTOHOB
E N E R G I E R E I C H E K E R N P H O T O E F F E K T E IN xaXPr Energieretche Kernphotoeffekte m I41pr wurden unter Verwendung des Restaktlvltatsverfahrens und yon Arbextswelsen der Gamma-Szmtlllatmnsspektroskopm studmrt Die bel Bestrahlung der Treffstellen yon Pr20 3 erhaltenen Ausbeuten yon Nd 14° wurden durch Bremsstrahlung mlt emem von 100 bls 300 MeV schwankenden Hochstwert yon Energte hestlmmt Die beobachteten la°Nd Ausbeuten deuten auf emen betrachthchen Bettrag yon sekundaren Protonenreakttonen hm 1. I N T R O D U C T I O N THIS p a p e r reports the results of a s t u d y of hxgh e n e r g y p h o t o n u c l e a r reactions i n praseodymmm Samples of PreO n were i r r a d i a t e d from the Umversxty of Illlnoxs 3 0 0 - M e V betatron, a n d use was m a d e of the residual actlvxty a n d g a m m a r a y scintillation spectroscopy techniques m ldentafying a n d s t u d y i n g the p r o d u c t nuclei T h e ta°Nd yield d a t a were c a l c u l a t e d a t several different b e t a t r o n operati n g energies P h o t o n u c l e a r reactxons i n praseod y m m m u p to 30 M e V were studmd a n d discussed previously (t)
2. E X P E R I M E N T A L T h e p r a s e o d y m m m target m a t e r i a l used m the b r e m s s t r a h l u n g i r r a d i a t i o n s was P r 6 0 n p o w d e r (99 9 per cent pure), a n d was o b t a i n e d from F a l r m o n t C h e m i c a l C o , Newark, N J. T h e samples weighed 5.00 g a n d were c o n t a i n e d i n lucite holders (3 699 c m 2 i n t e r n a l crosssection) t h a t were t h e n placed m the X - r a y b e a m . T h e b o m b a r d m e n t for each e x p e r i m e n t lasted for periods u p to 8 h r T h e r a n g e of b e t a t r o n o p e r a t i n g energies used e x t e n d e d from 100 M e V to 300 M e V m a x i m u m bremsstrahl u n g e n e r g y a n d with d a t a o b t a i n e d in most 153
154
El-Husszeny M. Dzefallah
051
0 30
~03
0 I(56
oBr
"x
•
lo2
IO5
.
;f..,. LO
I 80
] 160 Channel
I 240
I 320
l 400
I 480
number
Fio 1. Gamma ray spectrum of Pr6Oal irradiated with 160-MeV bremsstrahlung cases at 10-MeV energy intervals After the sample was irradiated, it was placed in a 50-ml beaker which was then placed on the top of a shielded 3 in × 3 in NaI(T1) crystal The resulting voltage pulses were fed into 512channel pulse height analyzer an order to determine the g a m m a ray spectrum The energy scale of the scintillation spectrometer was cahbrated and checked periodically with a number of standard g a m m a ray sources The decay of the irradiated samples was studied and the photopeaks were integrated in order to find the total number of counts observed Assignment of the g a m m a rays to their corresponding radioisotopes was made on the basis of their energies and half-hves All decay scheme reformations were obtained from consistent and recently published results (2) The various activIties produced at different betatron operating energies were checked for consistency an their half-lives The resulting g a m m a ray spectrum observed from a 6 0-hr irradiation at a betatron operating energy of 160 MeV, 1 hr after the end of irradiation is shown in Fig 1 The photopeaks that are present have energies of 0 166, 0"30, 0 511, 081 and 1 0 5 M e V The 0 1 6 6 M e V photopeak is due to la9Ce (140-day half-hfe) produced an the 141Pr (),, pn) lsgCe reaction The 0 30-, 0 81- and 0 05-MeV photopeaks are due to 13Spr (2-0-hr half-life) that is produced In the
a41Pr (y, 3n) aSSpr reaction The 0.511 MeV photopeak is due to anmhdatlon radiation associated with the positron emitters These include 139Nd (5"5-hr half-life), iSSNd (22-min half-hfe), 149pr (3.4-mln half-hfe) and 139pr (4 5-hr half-life) The 14°Nd (79 2-hr half-life) radioactivity measurements was made by observing the intensity of the 0 511 MeV annihilation gamma line of the 2 4 MeV /3+ of 14°pr present, at a long enough time after the end of irradiation, in secular equilibrium with 14°Nd Decay curve studies showed that the 0 511 MeV photopeak decayed with a clean 79 2-hr half-hfe after 60 hr Thus only data recorded after 60 hr were used to calculate 14°Nd yields as a function of betatron operating energy The reaction yield per monitor unit at the end of a number of irradiations each of duration T,, at a bremsstrahlung flux rate ~ , and with time intervals t~ between the end of the zth irradiation and total irradiation time, is Y =
N/At c ~ 4,(1
-
-
exp ( - - 2 T , ) ) exp (--2tj)
%3
where Y is the absolute yield value for the production of l~°Nd at a given betatron operating energy, N, the number of counts in time At in the photopeak, 2, the decay constant of 14°Nd and c, the detection efficiency of 14°Pr in the 0 511 MeV photopeak The flux rates, ~,, were monitored with a Wllson's quantameter (3) The ions produced by a given amount of X-ray energy are collected and measured by a vibrating reed electrometer The quantameter has the advantage that it has a response which is independent of energy It was calibrated during the time of these experiments against the National Bureau of Standards type P2 ionization chamber (4) We have also made use of the e2Cu radioactivity induced in copper foils by the (7% n) reaction on 63Cu as an lntercahbratlon monitor (s) All calibrations agreed to within experimental error The counting efficiency of the system combines a number of factors which correct for mode of decay, geometry, absorption, intrinsic crystal efficiency, peak to total ratio, positron annihilation efficiency, and the loss of counts from the 0 511 MeV photopeak due to the summing with bremsstrahlung associated with the positrons
Hzgh energyphotonudear reactzons m 141pr
Dead tame correctmns were unnecessary since counts of the 79-2-hr component were all for 100 per cent life tame The mode of decay correction gives the fraction of 14°Pr decay that goes by positron emission The value 0 54 given by GORODINISKII et al (6) and BIRYUKOVet al (7) was used The positron anmhllatmn efficmncy corrects for the incomplete anmhflatlon of positrons, whale the absorption factor represent correctmn due to g a m m a ray absorpuon m beaker and crystal housing Both factors were experimentally determined The mtnnsac efficiency of the crystal was determined from data given by V~OOR et al (s) The results were also corrected for the peak to total ratm (s) to obtain the total number of the 0 511 MeV g a m m a rays that interacted with the crystal, since not all photons that enter the crystal are counted an the photopeak 3. R E S U L T S A N D D I S C U S S I O N The observed ymld per monitor umt (9) of a4°Nd nuclei from high energy photonuclear reactmns in 14apr as a function ofbremsstrahlung m a m m u m energy xs shown an Fag 2 The 14°Nd activity is expected to be due to (7, or-n) reactmn on praseodymium The reactmn (7, ~--n) can be attributed to a m e c h a m s m an which a pion as created by the basic reactmn 7 + n --~ p+ + zr-, the paon escapes and the recoil proton as captured by the parent nucleus to form an excited compound nucleus which can then deexclte by evaporation of a neutron The threshold for such a process would be the creatmn energy of the pmn plus the banding energy of %
4o
o ,,.i,.. o....o ~ o...e.., o..--
x
.2
g
30
2 0
o~o~O~ '
/ o
/o
/0/./
~o
P I
IO0
the neutron Using the mass data of KoNio et al (lo), we find the threshold should be about 151 M e V I t is evident that there Is 14°Nd activity observed below the threshold for the 141pr (7, ~r-n) reaction This below-threshold activity is expected to be due to photonuclear reactions on impurities in the sample and secondary reactions caused by photoprotons that are produced in the betatron, the beam collimator and the target material Those from the target nuclei might be ejected protons from the dissociation of the neutron-proton pair in the quasldeuteron process on) or recoil protons from plon productlon (12) The target material used in these experiments IS 99"9~o pure P r 6 O l l and the impurity is mainly Nd~O 3 Photonuclear reactions on Nd203 showed that 14°Nd yields covering the same energy range used in these experiments is of the order of magnitude 106 reactions per monitor unit This eliminates the neodymium impurity as a significant source of background, so that 146Nd activity interfering with the 141pr (7, or-n) 14°Nd reaction must be due to secondary proton reactions The interfering secondary reactions are expected to be 141pr GO, 2n) a46Nd reaction Involving the main target isotope A sizeable fraction from processes in which a meson IS produced may also contribute to these secondary reactions, and an estimate of the events associated with the various processes cannot be made due to absence of enough detailed lnformatlons Since the probablhty of the secondary proton reactions would decrease for proton recoil energies above 30 MeV, (I3) then the increased 14°Nd yields at the higher energies indicate the importance of meson effects at these energtes (14) Further speculation on these points is of doubtfulvalue until more data are available. Acknowledgements--The author would hke to acknowledge the help and encouragement of Professor J P. HUMMEL Thanks are also due to the team of the Umverslty of Illinois betatron who performed the ~rradlat]ons.
>7.
0
155
1
150
l
200 Emox, MeV
I
250
]
300
FIG. 2 Yield data from the productmn of 14°Nd m Pr6Oll targets
REFERENCES 1 FERROROF , MALVANOR , SILVA E., GOL~EMSERO J. and MOSCATI G Nud Phys 10, 234 (1959) 2 NuclearData Sheets (Complied by K WAY et al ),
156
3 4.
5
6
7
El-Husszeny M Dzefallah Printing and Pubhshmg Office, Nattonal Academy of Scmnces--Natlonal Research Council, Washington 25, D C WILSONR R Nucl Instrum Meth 1, 101 (1957) HANsoN A O Intercahbratlon of Monitor on the Illinois 340 MeV Betatron, U of Illlnms Internal Report (March 1965) KOESTER L J , JR O n the Response of the Flat Ion Chambers, U of Illinois Internal Report (July 1958) GORODINISKIIG M , MURIN A N , POKROVSKII V N , PREOBRAZHENSKIIB K and TITOV N E Doklady Akad Nauk SSSR 112, 405, Soy Phys Doklady 2, 39 (1957) BIRYUKOVE I and SHIMANSKAYAN S , Izvest, Akad Nauk SSSR, Ser Fzz 26, 215 (1962), Golumbm Tech Trans 26, 215 (1962)
8 VEGORSS H , J R , MARSDEN L L and HEATH R L Phllhps Petroleum Company Atomic Energy Report, IDO 16370 (1958) 9 The response of the beam momtor xs not energy dependent. One momtor umt corresponds to 0 735 × 107 ergs of energy m the bremsstrahlung beam 10 KONIO L A , MATTAUCHJ H E and WAPSTRA A H Nucl Phys 31, 18 (1962). 11 LEVlNGERJ S. Phys Rev 84, 43 (1951) 12. BELLAMYE H Progr Nucl Phys 8, 237 (1960) 13 DOSTROVSKY I, FRAENKEL Z a n d FRIEDLANDER G Phys. Rev 116, 638 (1959) 14 VAI~ HIsE J R , MEYER R A and Htr~tMEL J P Phys. Rev 139, B554 (1965)
High Energy Photonuclear Reactions in 'lPr EL-HUSSIENY M DIEFALLAH Department of Chemistry, Assmt Umverstty, Assmt, Egypt Arab Republic
(Recewed 10 May 1971, m rewsedform 1 September 1971) Htgh energy photonuclear reactions m 141Pr were studied makmg use of the method of residual activity and gamma ray scintillation spectroscopy techniques The yield values of a4°Nd produced m irradiations of praseodymium oxide target were determined with bremsstrahlung of maximum energy varying from 100 to 300 MeV The observed 14°Nd ymlds mdmate that there ~s significant contribution from secondary proton reactions LES REACTIONS P H O T O N U C L E A I R E S DE HALITE ENERGIE DANS LE 141pr O n a dtudld les r6actlons photonucldalres de haute dnergxe dins le m P r , en utlhsant la mdthode d'actlvltd rdslduelle et les techniques de spectroscopm de scintillation aux rayons gamma. Les valeurs de rendement du xa°Nd prodult au eours des lrradmtlons d'une cxble d'oxyde de prasdodymtum ont dtd ddtermlndes avec des bremsstrahlung d'dnergm maximum qul vanalt de I00 h 300 MeV. Les rendements de la°Nd observ6s mdlquent qu'd y a une contribution sxgnlfiante des r6achons protomques secondalres (I)OTOYI~EPHLIE PEAHIIHH BbICOHO17I DHEPFHH B 14Ipr I48yqenr~ ~owog~eprtbie p e a ~ H B~COROfl~Heprn~ B 14tpr, genoaBay~ MeTO~ocTaTOqH0fi aHTHBHOCTH H CI~HHTHJIJIHI~HOHHhIe veXHnl~rl raMMa-cllei~wpocHon~t~t Onpe~eaeHbi 8Haqenn~ BHxoAa 14°Nd, noJiyqeHH~Ie B o 6 2 I y q e a n f l x Mtlmen~t OKrlCH n p a s e o a n M n U c TopMoaHMM HaJiyqeHHeM MaHC~IMa~bH0i~ 3HeprH~l B npeaeaax OT 100 ~0 300 MaB. Ha6~IOAeHHMe BI~IXO~M14°Nd noga3~tBamT Ha 8HaqiITeJii~ni)ii~ BHJIaA OT peami~Iil BTopHqHMX IIpOTOHOB
E N E R G I E R E I C H E K E R N P H O T O E F F E K T E IN xaXPr Energieretche Kernphotoeffekte m I41pr wurden unter Verwendung des Restaktlvltatsverfahrens und yon Arbextswelsen der Gamma-Szmtlllatmnsspektroskopm studmrt Die bel Bestrahlung der Treffstellen yon Pr20 3 erhaltenen Ausbeuten yon Nd 14° wurden durch Bremsstrahlung mlt emem von 100 bls 300 MeV schwankenden Hochstwert yon Energte hestlmmt Die beobachteten la°Nd Ausbeuten deuten auf emen betrachthchen Bettrag yon sekundaren Protonenreakttonen hm 1. I N T R O D U C T I O N THIS p a p e r reports the results of a s t u d y of hxgh e n e r g y p h o t o n u c l e a r reactions i n praseodymmm Samples of PreO n were i r r a d i a t e d from the Umversxty of Illlnoxs 3 0 0 - M e V betatron, a n d use was m a d e of the residual actlvxty a n d g a m m a r a y scintillation spectroscopy techniques m ldentafying a n d s t u d y i n g the p r o d u c t nuclei T h e ta°Nd yield d a t a were c a l c u l a t e d a t several different b e t a t r o n operati n g energies P h o t o n u c l e a r reactxons i n praseod y m m m u p to 30 M e V were studmd a n d discussed previously (t)
2. E X P E R I M E N T A L T h e p r a s e o d y m m m target m a t e r i a l used m the b r e m s s t r a h l u n g i r r a d i a t i o n s was P r 6 0 n p o w d e r (99 9 per cent pure), a n d was o b t a i n e d from F a l r m o n t C h e m i c a l C o , Newark, N J. T h e samples weighed 5.00 g a n d were c o n t a i n e d i n lucite holders (3 699 c m 2 i n t e r n a l crosssection) t h a t were t h e n placed m the X - r a y b e a m . T h e b o m b a r d m e n t for each e x p e r i m e n t lasted for periods u p to 8 h r T h e r a n g e of b e t a t r o n o p e r a t i n g energies used e x t e n d e d from 100 M e V to 300 M e V m a x i m u m bremsstrahl u n g e n e r g y a n d with d a t a o b t a i n e d in most 153
154
El-Husszeny M. Dzefallah
051
0 30
~03
0 I(56
oBr
"x
•
lo2
IO5
.
;f..,. LO
I 80
] 160 Channel
I 240
I 320
l 400
I 480
number
Fio 1. Gamma ray spectrum of Pr6Oal irradiated with 160-MeV bremsstrahlung cases at 10-MeV energy intervals After the sample was irradiated, it was placed in a 50-ml beaker which was then placed on the top of a shielded 3 in × 3 in NaI(T1) crystal The resulting voltage pulses were fed into 512channel pulse height analyzer an order to determine the g a m m a ray spectrum The energy scale of the scintillation spectrometer was cahbrated and checked periodically with a number of standard g a m m a ray sources The decay of the irradiated samples was studied and the photopeaks were integrated in order to find the total number of counts observed Assignment of the g a m m a rays to their corresponding radioisotopes was made on the basis of their energies and half-hves All decay scheme reformations were obtained from consistent and recently published results (2) The various activIties produced at different betatron operating energies were checked for consistency an their half-lives The resulting g a m m a ray spectrum observed from a 6 0-hr irradiation at a betatron operating energy of 160 MeV, 1 hr after the end of irradiation is shown in Fig 1 The photopeaks that are present have energies of 0 166, 0"30, 0 511, 081 and 1 0 5 M e V The 0 1 6 6 M e V photopeak is due to la9Ce (140-day half-hfe) produced an the 141Pr (),, pn) lsgCe reaction The 0 30-, 0 81- and 0 05-MeV photopeaks are due to 13Spr (2-0-hr half-life) that is produced In the
a41Pr (y, 3n) aSSpr reaction The 0.511 MeV photopeak is due to anmhdatlon radiation associated with the positron emitters These include 139Nd (5"5-hr half-life), iSSNd (22-min half-hfe), 149pr (3.4-mln half-hfe) and 139pr (4 5-hr half-life) The 14°Nd (79 2-hr half-life) radioactivity measurements was made by observing the intensity of the 0 511 MeV annihilation gamma line of the 2 4 MeV /3+ of 14°pr present, at a long enough time after the end of irradiation, in secular equilibrium with 14°Nd Decay curve studies showed that the 0 511 MeV photopeak decayed with a clean 79 2-hr half-hfe after 60 hr Thus only data recorded after 60 hr were used to calculate 14°Nd yields as a function of betatron operating energy The reaction yield per monitor unit at the end of a number of irradiations each of duration T,, at a bremsstrahlung flux rate ~ , and with time intervals t~ between the end of the zth irradiation and total irradiation time, is Y =
N/At c ~ 4,(1
-
-
exp ( - - 2 T , ) ) exp (--2tj)
%3
where Y is the absolute yield value for the production of l~°Nd at a given betatron operating energy, N, the number of counts in time At in the photopeak, 2, the decay constant of 14°Nd and c, the detection efficiency of 14°Pr in the 0 511 MeV photopeak The flux rates, ~,, were monitored with a Wllson's quantameter (3) The ions produced by a given amount of X-ray energy are collected and measured by a vibrating reed electrometer The quantameter has the advantage that it has a response which is independent of energy It was calibrated during the time of these experiments against the National Bureau of Standards type P2 ionization chamber (4) We have also made use of the e2Cu radioactivity induced in copper foils by the (7% n) reaction on 63Cu as an lntercahbratlon monitor (s) All calibrations agreed to within experimental error The counting efficiency of the system combines a number of factors which correct for mode of decay, geometry, absorption, intrinsic crystal efficiency, peak to total ratio, positron annihilation efficiency, and the loss of counts from the 0 511 MeV photopeak due to the summing with bremsstrahlung associated with the positrons
Hzgh energyphotonudear reactzons m 141pr
Dead tame correctmns were unnecessary since counts of the 79-2-hr component were all for 100 per cent life tame The mode of decay correction gives the fraction of 14°Pr decay that goes by positron emission The value 0 54 given by GORODINISKII et al (6) and BIRYUKOVet al (7) was used The positron anmhllatmn efficmncy corrects for the incomplete anmhflatlon of positrons, whale the absorption factor represent correctmn due to g a m m a ray absorpuon m beaker and crystal housing Both factors were experimentally determined The mtnnsac efficiency of the crystal was determined from data given by V~OOR et al (s) The results were also corrected for the peak to total ratm (s) to obtain the total number of the 0 511 MeV g a m m a rays that interacted with the crystal, since not all photons that enter the crystal are counted an the photopeak 3. R E S U L T S A N D D I S C U S S I O N The observed ymld per monitor umt (9) of a4°Nd nuclei from high energy photonuclear reactmns in 14apr as a function ofbremsstrahlung m a m m u m energy xs shown an Fag 2 The 14°Nd activity is expected to be due to (7, or-n) reactmn on praseodymium The reactmn (7, ~--n) can be attributed to a m e c h a m s m an which a pion as created by the basic reactmn 7 + n --~ p+ + zr-, the paon escapes and the recoil proton as captured by the parent nucleus to form an excited compound nucleus which can then deexclte by evaporation of a neutron The threshold for such a process would be the creatmn energy of the pmn plus the banding energy of %
4o
o ,,.i,.. o....o ~ o...e.., o..--
x
.2
g
30
2 0
o~o~O~ '
/ o
/o
/0/./
~o
P I
IO0
the neutron Using the mass data of KoNio et al (lo), we find the threshold should be about 151 M e V I t is evident that there Is 14°Nd activity observed below the threshold for the 141pr (7, ~r-n) reaction This below-threshold activity is expected to be due to photonuclear reactions on impurities in the sample and secondary reactions caused by photoprotons that are produced in the betatron, the beam collimator and the target material Those from the target nuclei might be ejected protons from the dissociation of the neutron-proton pair in the quasldeuteron process on) or recoil protons from plon productlon (12) The target material used in these experiments IS 99"9~o pure P r 6 O l l and the impurity is mainly Nd~O 3 Photonuclear reactions on Nd203 showed that 14°Nd yields covering the same energy range used in these experiments is of the order of magnitude 106 reactions per monitor unit This eliminates the neodymium impurity as a significant source of background, so that 146Nd activity interfering with the 141pr (7, or-n) 14°Nd reaction must be due to secondary proton reactions The interfering secondary reactions are expected to be 141pr GO, 2n) a46Nd reaction Involving the main target isotope A sizeable fraction from processes in which a meson IS produced may also contribute to these secondary reactions, and an estimate of the events associated with the various processes cannot be made due to absence of enough detailed lnformatlons Since the probablhty of the secondary proton reactions would decrease for proton recoil energies above 30 MeV, (I3) then the increased 14°Nd yields at the higher energies indicate the importance of meson effects at these energtes (14) Further speculation on these points is of doubtfulvalue until more data are available. Acknowledgements--The author would hke to acknowledge the help and encouragement of Professor J P. HUMMEL Thanks are also due to the team of the Umverslty of Illinois betatron who performed the ~rradlat]ons.
>7.
0
155
1
150
l
200 Emox, MeV
I
250
]
300
FIG. 2 Yield data from the productmn of 14°Nd m Pr6Oll targets
REFERENCES 1 FERROROF , MALVANOR , SILVA E., GOL~EMSERO J. and MOSCATI G Nud Phys 10, 234 (1959) 2 NuclearData Sheets (Complied by K WAY et al ),
156
3 4.
5
6
7
El-Husszeny M Dzefallah Printing and Pubhshmg Office, Nattonal Academy of Scmnces--Natlonal Research Council, Washington 25, D C WILSONR R Nucl Instrum Meth 1, 101 (1957) HANsoN A O Intercahbratlon of Monitor on the Illinois 340 MeV Betatron, U of Illlnms Internal Report (March 1965) KOESTER L J , JR O n the Response of the Flat Ion Chambers, U of Illinois Internal Report (July 1958) GORODINISKIIG M , MURIN A N , POKROVSKII V N , PREOBRAZHENSKIIB K and TITOV N E Doklady Akad Nauk SSSR 112, 405, Soy Phys Doklady 2, 39 (1957) BIRYUKOVE I and SHIMANSKAYAN S , Izvest, Akad Nauk SSSR, Ser Fzz 26, 215 (1962), Golumbm Tech Trans 26, 215 (1962)
8 VEGORSS H , J R , MARSDEN L L and HEATH R L Phllhps Petroleum Company Atomic Energy Report, IDO 16370 (1958) 9 The response of the beam momtor xs not energy dependent. One momtor umt corresponds to 0 735 × 107 ergs of energy m the bremsstrahlung beam 10 KONIO L A , MATTAUCHJ H E and WAPSTRA A H Nucl Phys 31, 18 (1962). 11 LEVlNGERJ S. Phys Rev 84, 43 (1951) 12. BELLAMYE H Progr Nucl Phys 8, 237 (1960) 13 DOSTROVSKY I, FRAENKEL Z a n d FRIEDLANDER G Phys. Rev 116, 638 (1959) 14 VAI~ HIsE J R , MEYER R A and Htr~tMEL J P Phys. Rev 139, B554 (1965)