ENTRY 14134 20160315 14161413400000001 SUBENT 14134001 20160315 14161413400100001 BIB 13 47 1413400100002 TITLE Fission Neutron Spectrum of 235U 1413400100003 AUTHOR (N.Nereson) 1413400100004 REFERENCE (J,PR,85,(4),600,1952) 1413400100005 #doi:10.1103/PhysRev.85.600 1413400100006 REL-REF (M,,N.Nereson+,J,RSI,21,534,1950) 1413400100007 INSTITUTE (1USALAS) 1413400100008 FACILITY (REAC,1USALAS) Los Alamos fast reactor. 1413400100009 INC-SOURCE (REAC) Thermal neutron neutrons emerging from the 1413400100010 water boiler had a cadmium ratio of about 500 and, at 1413400100011 a power of 5.5 kilowatts, the flux at a position of 1413400100012 the foil was 6x10**5 neutrons/cm2/sec. 1413400100013 DETECTOR (PLATE) Ilford C2 nuclear emulsion plates, 100 microns 1413400100014 thick. 1413400100015 SAMPLE A 10-mil thickness of 235UO3 was coated on a 1/32-inch 1413400100016 thick aluminum strip measuring 1x4 inches. 1413400100017 METHOD (REC) The uranium foil was placed approximately 1413400100018 perpendicular with the aluminum side facing the beam. 1413400100019 Nuclear emulsion plates were placed outside of the 1413400100020 neutron beam at a distance of 16 cm from the nearest 1413400100021 edge of the foil. A 15-hour run at a power of 5.5 kW 1413400100022 gave an appropriate proton recoil density on the 1413400100023 nuclear plates. A background experiment was performed 1413400100024 by removing the 235U foil and substituting a piece of 1413400100025 aluminum. 1413400100026 ANALYSIS The nuclear plates were analyzed by the method of 1413400100027 measuring recoils about the a small angle of the 1413400100028 forward neutron direction. In order to obtain the 1413400100029 true number of proton recoil tracks, the number of 1413400100030 measured tracks must be corrected for those tracks 1413400100031 leaving the emulsion surfaces. The number of 1413400100032 corrected proton recoil tracks is proportional to the 1413400100033 collision cross section of hydrogen (sigma p) and to 1413400100034 the incoming neutron flux. The neutron spectrum or 1413400100035 N(E) can then be obtained after correcting the 1413400100036 measured tracks for recoils leaving the emulsion 1413400100037 surface and sigma p. Since it is desirable to plot the 1413400100038 spectral curve in terms of neutron energy E rather 1413400100039 than proton recoil energy Ep, it is necessary to 1413400100040 convert the track data from Ep to E. Tracks on the 1413400100041 background plate were less than 5% of the number of 1413400100042 measured tracks on the regular data plate. Therefore, 1413400100043 the background was neglected in the analysis of the 1413400100044 data. Unfortunately, this method does not allow to 1413400100045 discriminate between prompt and delayed neutrons. 1413400100046 ERR-ANALYS (DATA-ERR) No details are given. 1413400100047 HISTORY (20140917C) BP 1413400100048 (20160315A) OS. ASSUM replaced by MONIT in sub.2 1413400100049 ENDBIB 47 0 1413400100050 COMMON 1 3 1413400100051 EN 1413400100052 EV 1413400100053 0.0253 1413400100054 ENDCOMMON 3 0 1413400100055 ENDSUBENT 54 0 1413400199999 SUBENT 14134002 20160315 14161413400200001 BIB 5 8 1413400200002 REACTION (92-U-235(N,F),,NU/DE,,REL) 1413400200003 Neutron flux in relative units 1413400200004 MONITOR (1-H-1(N,EL)1-H-1,,SIG) 1413400200005 FLAG (1.) This result at E=0.39 MeV has been increased by 1413400200006 20% to adjust for emulsion inefficiency at lower 1413400200007 energies. 1413400200008 STATUS (TABLE) Table I, page 602. 1413400200009 HISTORY (20160315A) ASSUMED replaced by MONITOR 1413400200010 ENDBIB 8 0 1413400200011 NOCOMMON 0 0 1413400200012 DATA 5 19 1413400200013 E DATA DATA-ERR MONIT FLAG 1413400200014 MEV ARB-UNITS ARB-UNITS B NO-DIM 1413400200015 0.39 58.6 3.6 7.15 1. 1413400200016 0.48 49.5 3.3 6.25 1413400200017 0.56 57.0 3.8 5.85 1413400200018 0.68 61.8 3.0 5.35 1413400200019 0.80 63.5 3.3 4.90 1413400200020 0.98 54.4 2.4 4.45 1413400200021 1.20 55.7 2.6 4.00 1413400200022 1.44 48.5 2.2 3.60 1413400200023 1.75 42.2 2.0 3.20 1413400200024 2.18 37.9 1.7 2.80 1413400200025 2.71 30.0 1.6 2.45 1413400200026 3.24 16.3 1.3 2.18 1413400200027 3.78 11.5 1.1 1.98 1413400200028 4.39 10.6 1.2 1.78 1413400200029 4.95 6.0 1.1 1.63 1413400200030 5.48 7.1 1.3 1.52 1413400200031 6.03 4.9 1.2 1.42 1413400200032 6.55 2.5 0.9 1.33 1413400200033 7.02 0.45 0.5 1.28 1413400200034 ENDDATA 21 0 1413400200035 ENDSUBENT 34 0 1413400299999 ENDENTRY 2 0 1413499999999