ENTRY 14606 20200410 14711460600000001 SUBENT 14606001 20200410 14711460600100001 BIB 11 51 1460600100002 TITLE Fission fragment angular anisotropy in 1460600100003 neutron-induced fission of 235U measured with a time 1460600100004 projection chamber 1460600100005 AUTHOR (V.Geppert-Kleinrath,F.Tovesson,J.S.Barrett,N.S.Bowden,1460600100006 J.Bundgaard,R.J.Casperson,D.A.Cebra,T.Classen, 1460600100007 M.Cunningham,D.L.Duke,J.Gearhart,U.Greife, 1460600100008 E.Guardincerri,C.Hagmann,M.Heffner,D.Hensle, 1460600100009 D.Higgins,L.D.Isenhower,J.King,J.L.Klay,W.Loveland, 1460600100010 J.A.Magee,B.Manning,M.P.Mendenhall,J.Ruz,S.Sangiorgio, 1460600100011 K.T.Schmitt,B.Seilhan,L.Snyder,A.C.Tate,R.S.Towell, 1460600100012 N.Walsh,S.Watson,L.Yao,W.Younes,H.Leeb) 1460600100013 INSTITUTE (1USALAS,1USAORU,1USALRL,1USACSM,1USADAV,2AUSTHV) 1460600100014 (1USAUSA) Abilene Christian University, Abilene, Texas 1460600100015 (1USAUSA) California Polytechnic State University, 1460600100016 San Luis Obispo, California 1460600100017 REFERENCE (J,PR/C,99,064619,2019) 1460600100018 FACILITY (LINAC,1USALAS) Experiment performed at LANSCE 800 1460600100019 MeV linear proton accelerator at the Los Alamos 1460600100020 SAMPLE (92-U-235,ENR=0.995) Trace contaminants of 233,234,236 1460600100021 and 238U was lower than 0.5%.The 235U layer with 1460600100022 thickness of 50 mu-g/cm2 and diameter of 20 mm was 1460600100023 deposited on 0.5mm Al backing 1460600100024 DETECTOR Time projection chamber was used in this experiment. 1460600100025 It consisted of a cylindrical chamber with radius of 1460600100026 7.5 cm and length of 11 cm filled with 95% Ar and 5% 1460600100027 isobutane gas mixture at 550 Torr. TPC has two 1460600100028 pixelated MICROMEGAS anode planes with 2976 hexagonal 1460600100029 channels each and ethernet-based data acquisition 1460600100030 electronics. TPC provides information on fission 1460600100031 fragment track, charge and specific ionization. 1460600100032 Energy cut of 44.4 MeV was used to distinguish fission 1460600100033 from recoil ions and other particles. 1460600100034 METHOD (TOF) Incident neutron energy was determined by time- 1460600100035 of-flight. Pulsed proton beam with frequency 100 Hz 1460600100036 and and macropulse width of 625 mu-s had average 1460600100037 current of 1.5 mu-A. Each macropulse consisted of a 1460600100038 series micropulses with length less than 250 ps. 1460600100039 Two signals to determine time of flight were 1460600100040 accelerator signal and fission TPC cathode signal. 1460600100041 INC-SOURCE (SPALL) Neutrons were produced by spallation reaction 1460600100042 of 800 MeV protons on tungsten target using Target-4 1460600100043 and 90L flightpath. This is high energy white neutron 1460600100044 source producing neutrons at energies from 0.1 MeV to 1460600100045 greater than 600 MeV. 1460600100046 ANALYSIS Since 235U deposit was on thick backing, only signal 1460600100047 from one fission fragment was used. The angular 1460600100048 distributions are fit with the Legendre polynomials. 1460600100049 The anisotropy is equal to the sum of the coefficients 1460600100050 in the polynomial fit equation. The anisotropy result 1460600100051 is derived using second order Legendre polynomials only1460600100052 HISTORY (20200410C) Compiled by S.H. 1460600100053 ENDBIB 51 0 1460600100054 NOCOMMON 0 0 1460600100055 ENDSUBENT 54 0 1460600199999 SUBENT 14606002 20200410 14711460600200001 BIB 3 16 1460600200002 REACTION (92-U-235(N,F),,DA,FF,RSD) 1460600200003 Anisotropy parameter = W(0deg)/W(90deg) 1460600200004 ERR-ANALYS (ERR-1,1.,6.) Systematic uncertainty from fit of 1460600200005 angular distribution 1460600200006 (ERR-2,0.5,3.) Systematic uncertainty from fission 1460600200007 fragment identification 1460600200008 (ERR-3,0.5,3.) Systematic uncertainty from limited 1460600200009 angular range of fit 1460600200010 (ERR-4,0.5,1.) Systematic uncertainty caused by 1460600200011 uncertainty in the drift speed. 1460600200012 (ERR-S) Statistical uncertainty 1460600200013 (ERR-T) Total uncertainty consisting of statistical 1460600200014 uncertainty plus all considered systematic 1460600200015 uncertainties added in quadrature 1460600200016 STATUS (TABLE) Data taken from Supplemental Material http:// 1460600200017 link.aps.org/supplemental/10.1103/PhysRevC.99.064619 1460600200018 ENDBIB 16 0 1460600200019 COMMON 1 3 1460600200020 ANG 1460600200021 ADEG 1460600200022 0. 1460600200023 ENDCOMMON 3 0 1460600200024 DATA 6 35 1460600200025 EN EN-RSL DATA -ERR-T +ERR-T ERR-S 1460600200026 MEV MEV NO-DIM NO-DIM NO-DIM NO-DIM 1460600200027 0.18 0.02 1.012 0.021 0.024 0.012 1460600200028 0.25 0.05 1.047 0.031 0.015 0.010 1460600200029 0.35 0.05 1.071 0.036 0.011 0.011 1460600200030 0.45 0.05 1.076 0.033 0.013 0.011 1460600200031 0.55 0.05 1.112 0.020 0.014 0.011 1460600200032 0.65 0.05 1.114 0.035 0.014 0.011 1460600200033 0.75 0.05 1.127 0.031 0.016 0.012 1460600200034 0.85 0.05 1.106 0.041 0.017 0.011 1460600200035 0.95 0.05 1.149 0.020 0.015 0.012 1460600200036 1.09 0.09 1.183 0.028 0.015 0.011 1460600200037 1.28 0.11 1.177 0.025 0.014 0.011 1460600200038 1.51 0.12 1.187 0.042 0.017 0.011 1460600200039 1.78 0.15 1.186 0.031 0.013 0.011 1460600200040 2.10 0.17 1.208 0.020 0.012 0.011 1460600200041 2.48 0.20 1.199 0.024 0.013 0.011 1460600200042 2.92 0.24 1.187 0.021 0.012 0.011 1460600200043 3.44 0.28 1.161 0.022 0.013 0.011 1460600200044 4.06 0.33 1.170 0.018 0.012 0.011 1460600200045 4.79 0.39 1.140 0.024 0.012 0.011 1460600200046 5.64 0.46 1.158 0.024 0.013 0.012 1460600200047 6.65 0.55 1.313 0.022 0.014 0.013 1460600200048 7.84 0.64 1.352 0.032 0.014 0.013 1460600200049 9.24 0.76 1.306 0.023 0.013 0.013 1460600200050 10.89 0.89 1.272 0.025 0.018 0.013 1460600200051 12.84 1.05 1.295 0.036 0.021 0.013 1460600200052 15.14 1.24 1.337 0.033 0.015 0.014 1460600200053 17.84 1.46 1.303 0.064 0.021 0.014 1460600200054 23.07 3.76 1.298 0.050 0.018 0.012 1460600200055 32.05 5.22 1.258 0.035 0.017 0.012 1460600200056 44.54 7.26 1.214 0.059 0.016 0.012 1460600200057 61.88 10.09 1.138 0.072 0.023 0.012 1460600200058 85.98 14.02 1.108 0.078 0.026 0.012 1460600200059 119.48 19.47 1.040 0.074 0.029 0.013 1460600200060 166.01 27.06 1.022 0.076 0.025 0.016 1460600200061 230.67 37.60 0.968 0.090 0.052 0.023 1460600200062 ENDDATA 37 0 1460600200063 ENDSUBENT 62 0 1460600299999 ENDENTRY 2 0 1460699999999