ENTRY 23146 20110825 22282314600000001 SUBENT 23146001 20110825 22282314600100001 BIB 16 107 2314600100002 TITLE Direct evidence for inelastic neutron "acceleration" 2314600100003 by Lu-177m. 2314600100004 AUTHOR (O.Roig, V.Meot, B.Rosse, G.Belier,J.-M.Daugas, 2314600100005 A.Letourneau, A.Menelle, P.Morel) 2314600100006 INSTITUTE (2FR BRC) O.Roig,V.Meot,B.Rosse,G.Belier,J.-M.Daugas, 2314600100007 P.Morel 2314600100008 (2FR SAC) A.Letourneau (CEA/DSM/Irfu/SPhN) 2314600100009 (2FR SAC) A.Menelle (CEA/DSM/LLB) 2314600100010 REFERENCE (J,PR/C,83,064617,2011) 2314600100011 #doi:10.1103/PhysRevC.83.064617 2314600100012 INC-SOURCE (REAC) Neutron beam is collimated to diameter of 2 cm 2314600100013 by sandwich of 0.5-cm-thick boron carbide (B4C) neutron2314600100014 absorber, followed by a 1-cm-thick polyethylene (CH2) 2314600100015 layer, 2-cm-thick lead (Pb) gamma-attenuator placed 2314600100016 1.8 m upstream from the target. Second collimator of 2314600100017 1-cm-thick B4C and 5-cm-thick Pb layer is placed 25 cm 2314600100018 from the target to eliminate neutrons scattered on the 2314600100019 first collimator. 2314600100020 INC-SPECT Cold neutron beam. 2314600100021 Initial neutron flux of 1.5E+9 n/cm**2/s for mean 2314600100022 energy of 4.5 meV and angular spreading of 0.4 degree. 2314600100023 Using the value and the Lu-176m activation measurement,2314600100024 neutron flux of (1.71+-0.16)*10**8 n/cm**2/s was 2314600100025 obtained on the target. 2314600100026 FACILITY (REAC,2FR SAC) Neutron multidetector array at the 2314600100027 ORPHEE 14-MW reactor facility. G3.2 experimental area 2314600100028 located about 40 m away from the reactor core. 2314600100029 (REAC,2FR ILL) HFR reactor - to produce Lu-177m sample.2314600100030 SAMPLE Natural lutetium foil (25 microm thickness) of mass 2314600100031 10.24+-0.01 mg in Al capsule was irradiated during 2314600100032 6 days at the high flux reactor (maximum neutron flux 2314600100033 around 1.5E15 n/cm**2/s) to produce Lu-177m by the 2314600100034 Lu-176 radiative capture reaction. After 150-day 2314600100035 cooling time it was put inside thin pure Al envelope 2314600100036 of 20 microm thick. The number of (1.03+-0.05)*10**14 2314600100037 isomers was accurately measured by gamma-spectroscopy 2314600100038 right before the experiment at the ORPHEE facility. 2314600100039 The activity of this radioactive target was 13.22 MBq. 2314600100040 A similar nonirradiated natural lutetium foil from the 2314600100041 same natural Lu sample used for the isomer target was 2314600100042 used as a blank target. 2314600100043 DETECTOR (PROPC) 10-bar pure He-3 proportional counter of outer 2314600100044 diameter 2.54 cm, active length 25 cm. Neutron array 2314600100045 consists of 12 proportional 3He counters placed inside 2314600100046 the cylindrical polyethylene moderator. 2314600100047 Inner part of the vacuum chamber is shielded by 2314600100048 2-mm-thick Cd layer to suppress the neutrons scattered 2314600100049 by the target. 1-mm-thick Cd layer covers the moderator2314600100050 to stop thermal neutrons from the background or cold 2314600100051 neutrons scattered by the collimator. 2314600100052 Detection efficiency of the neutron array was obtained 2314600100053 from MCNP code simulations - mean efficiency of 19.8%. 2314600100054 Cf-252 source spontaneous fission neutron spectrum was 2314600100055 measure and simulated by MCNP code to define 2314600100056 correction factor. Corrected detection efficiency is 2314600100057 (18.4+-0.9)%. 2314600100058 (SPEC) Low-energy photon spectrometer (LEPS) was used 2314600100059 to measure the 88.361-keV gamma-ray from the beta-decay2314600100060 of Lu-176m. Gamma detection efficiency of the LEPS 2314600100061 located at (55.1+-0.5) cm was carefully obtained using 2314600100062 standard radioactive sources (133Ba, 152Eu, 241Am) and 2314600100063 MCNP and GEANT4 simulations to be (2.3+-0.1)*10**-3 %. 2314600100064 METHOD (ACTIV) 2314600100065 (GSPEC) 2314600100066 Counting rates for various configurations were obtained2314600100067 from integrals of thermal neutron peaks at 764 keV. 2314600100068 N Target Counting rate (cps) +-sta+-sys er2314600100069 1 177Lum (4.07+-0.01+-0.08) 2314600100070 2 Natural Lu 14 mg (2.86+-0.01+-0.08) 2314600100071 3 Natural Lu 12.2 mg (2.87+-0.01+-0.08) 2314600100072 4 Natural Lu 6.8 mg (2.79+-0.01+-0.08) 2314600100073 5 No (2.565+-0.005+-0.08) 2314600100074 6 Al envelope alone (2.637+-0.003+-0.08) 2314600100075 7 177Lum (2.690+-0.010+-0.08) 2314600100076 8 177Lum (1.139+-0.003+-0.08) 2314600100077 9 No (1.21+-0.04+-0.08) 2314600100078 For N 1-7 - beam is inside the cave, where the neutron2314600100079 detector and the isomeric target are located, 2314600100080 for N 8-9 - beam off. 2314600100081 For N 7 - block made in B4C in front of the isomeric 2314600100082 target, letting the neutron beam come inside the 2314600100083 experimental cave, for others - out. 2314600100084 MONITOR ((MONIT)71-LU-175(N,G)71-LU-176-M,,SIG) Cross sections 2314600100085 of the burn-up of 175-Lu was used to derive neutron 2314600100086 flux at sample position using the initial Lu-175 2314600100087 quantity, the neutron flux in the V4 port ILL 2314600100088 high-flux reactor. 2314600100089 In the ORPHEE G3.2 cold neutron flux, 175Lu(n,G)176Lum 2314600100090 cross section was derived from c-s value at thermal 2314600100091 point (16.7+-0.4) b using 1/v law to be (41.5+-1.0) b. 2314600100092 MONIT-REF (,S.F.Mughabghab,B,NEUT.RES,,2007) 2314600100093 DECAY-DATA (71-LU-176-M,3.664HR,DG,88.361) 2314600100094 (71-LU-177-M,160.D) 2314600100095 CORRECTION For gamma-ray self-absorption. 2314600100096 For backgrounds: high activity of the target, 2314600100097 background arising from the collimating of the beam, 2314600100098 neutron scattering on the target and neutrons from the 2314600100099 environment (presence of the reactor, natural 2314600100100 radioactivity). 2314600100101 ADD-RES Calculated (using Gilbert-Cameron formula, gamma-ray 2314600100102 strength function of Kopecky and Uhl, resonance 2314600100103 radiative widths of Lu-175, Lu-176, deformed optical 2314600100104 potential) average resonance parameters: 2314600100105 D0=1.4 eV, =55-95 meV, 2314600100106 =1.E-2 meV, =6 meV. 2314600100107 From Table IV of J,PR/C,83,064617,2011. 2314600100108 HISTORY (20110825C) M.M. 2314600100109 ENDBIB 107 0 2314600100110 COMMON 3 3 2314600100111 EN-NRM MONIT MONIT-ERR 2314600100112 EV B B 2314600100113 0.025 16.7 0.4 2314600100114 ENDCOMMON 3 0 2314600100115 ENDSUBENT 114 0 2314600199999 SUBENT 23146002 20110825 22282314600200001 BIB 4 9 2314600200002 REACTION (71-LU-177-M(N,INL)71-LU-177,,SIG,,SPA) 2314600200003 Measured on ORPHEE spectrum. 2314600200004 ANALYSIS Inelastic neutron acceleration cross-section was 2314600200005 derived by the neutron flux, the detection efficiency, 2314600200006 and the number of 177Lu isomers. 2314600200007 ERR-ANALYS (DATA-ERR) Supposed as total by compiler. 2314600200008 STATUS (TABLE) Text,page 064617-4, of J,PR/C,83,064617,2011. 2314600200009 (COREL,22950008) In 22950.008 -indirect measurement at 2314600200010 Maxwellian neutron flux of T=323 K. 2314600200011 ENDBIB 9 0 2314600200012 NOCOMMON 0 0 2314600200013 DATA 5 1 2314600200014 EN DATA DATA-ERR MONIT MONIT-ERR 2314600200015 MILLI-EV B B B B 2314600200016 4.5 363. 48. 41.5 1.0 2314600200017 ENDDATA 3 0 2314600200018 ENDSUBENT 17 0 2314600299999 SUBENT 23146003 20110825 22282314600300001 BIB 3 16 2314600300002 REACTION 1(71-LU-177-M(N,0),,EN) 2314600300003 2(71-LU-177-M(N,EL),,WID) 2314600300004 3(71-LU-177-M(N,G),,WID) 2314600300005 ANALYSIS Integrated cross section has been calculated over 2314600300006 a Maxwellian neutron energy distribution at T = 323 K 2314600300007 and over the ORPHEE G3.2 neutron energy distribution, 2314600300008 then described by the Breit-Wigner formula with one 2314600300009 isolated resonance. Resonance energy, the radiative 2314600300010 width, the neutron width, are adjusted on the 2314600300011 Maxwellian averaged radiative capture cross section. 2314600300012 This set of obtained parameters is not unique but it 2314600300013 allows the relevance of the presence of a low energy 2314600300014 resonance to be tested. 2314600300015 Superelastic neutron width is fixed at 70% of the 2314600300016 radiative width. 2314600300017 STATUS (TABLE) Table III of J,PR/C,83,064617,2011. 2314600300018 ENDBIB 16 0 2314600300019 NOCOMMON 0 0 2314600300020 DATA 3 1 2314600300021 DATA 1DATA 2DATA 3 2314600300022 EV MILLI-EV MILLI-EV 2314600300023 0.15 1.8E-2 50. 2314600300024 ENDDATA 3 0 2314600300025 ENDSUBENT 24 0 2314600399999 SUBENT 23146004 20110825 22282314600400001 BIB 3 7 2314600400002 REACTION (71-LU-177-M(N,INL)71-LU-177,,SIG,,SPA,DERIV) 2314600400003 ANALYSIS Inelastic neutron acceleration cross-section was 2314600400004 derived with resonance parameters, 2314600400005 for ORPHEE spectrum. 2314600400006 Agree with measured - Subent 002. 2314600400007 STATUS (TABLE) Text,page 064617-5, of J,PR/C,83,064617,2011. 2314600400008 (DEP,23146003) Res.parameters used. 2314600400009 ENDBIB 7 0 2314600400010 NOCOMMON 0 0 2314600400011 DATA 2 1 2314600400012 EN DATA 2314600400013 MILLI-EV B 2314600400014 4.5 374. 2314600400015 ENDDATA 3 0 2314600400016 ENDSUBENT 15 0 2314600499999 SUBENT 23146005 20110825 22282314600500001 BIB 4 9 2314600500002 REACTION (71-LU-177-M(N,INL)71-LU-177,,SIG,,MXW,DERIV) 2314600500003 REL-REF (A,22950008,O.Roig+,J,PR/C,74,054604,2006) 2314600500004 Agree with indirect measurement - 258+-58 b. 2314600500005 ANALYSIS Inelastic neutron acceleration cross-section was 2314600500006 derived with resonance parameters, 2314600500007 for Maxwellian spectrum at T=323 K. 2314600500008 Agree with measured - Subent 002. 2314600500009 STATUS (TABLE) Text,page 064617-5, of J,PR/C,83,064617,2011. 2314600500010 (DEP,23146003) Res.parameters used. 2314600500011 ENDBIB 9 0 2314600500012 NOCOMMON 0 0 2314600500013 DATA 2 1 2314600500014 EN DATA 2314600500015 MILLI-EV B 2314600500016 4.5 260. 2314600500017 ENDDATA 3 0 2314600500018 ENDSUBENT 17 0 2314600599999 ENDENTRY 5 0 2314699999999