ENTRY 10102 20000202 00001010200000001 SUBENT 10102001 20000202 00001010200100001 BIB 14 48 1010200100002 INSTITUTE (1USADAV) 1010200100003 REFERENCE (J,PRL,25,1628,197012) 1010200100004 AUTHOR (F.P.BRADY,W.J.KNOX,J.A.JUNGERMAN,M.R.MC GIE, 1010200100005 R.L.WALRAVEN) 1010200100006 TITLE Precise measurement of neutron-proton total cross 1010200100007 section from 25 to 60 MeV. 1010200100008 FACILITY (CYCLO) Crocker isochronous cyclotron. 1010200100009 INC-SOURCE (P-LI7) Metallic Li target. 7Li(p,n) neutrons. 1010200100010 INC-SPECT Roughly 60% source neutrons fall within well-defined 1010200100011 high energy peak about 2 MeV wide. Rest spread over 1010200100012 broad low energy tail. Peak selected by time-of- 1010200100013 flight. Mean energy of beam determined to better than 1010200100014 100 keV. 1010200100015 SAMPLE Pure polyethylene and spectrogaphic grade graphite. H/C1010200100016 ratio of polyethylene sample chemically determined to 1010200100017 about 0.2%. Samples 63 to 127 mm long. 1010200100018 METHOD Transmission geometry, with counter telescopes 1010200100019 before and after sample. 1010200100020 DETECTOR (TELES) Three counter telescopes used, each containing 1010200100021 a veto scintillator, CH2 converter, and two thin 1010200100022 (1 mm) scintillators separated by a copper absorber. 1010200100023 Telescopes insensitive to gammas. Neutron detection 1010200100024 efficiency about 1%. 1010200100025 One telescope before sample, two following. Distance 1010200100026 from 7Li source to sample center- 4 m. Distance from 1010200100027 sample to point between two following telescopes- 3.5m1010200100028 CORRECTION Following corrections made: 1010200100029 . background due to neutrons scattered out of sample 1010200100030 and rescattered into detector (+0.05%), 1010200100031 . single scatter inscattering (+0.01%) (multiple 1010200100032 scattering estimated approximately 1/10 single 1010200100033 scattering correction), 1010200100034 . deadtime (+0.3%), 1010200100035 . displacement of air by sample (+0.2%), 1010200100036 . finite energy width (-0.02%), 1010200100037 . C/H ratio (-0.9%), 1010200100038 . air displacement in sample weighing (-0.3%), 1010200100039 . isotopic composition (+0.06%). 1010200100040 ERR-ANALYS (DATA-ERR) Statistics, plus folding in of 20% of 1010200100041 background correction and 30% of deadtime correction. 1010200100042 Also includes uncertainty in energy. 1010200100043 Systematic uncertainty of 0.3% on all points due to 1010200100044 H/C ratio and sample size uncertainties not included. 1010200100045 STATUS (APRVD) Approved by author. 1010200100046 HISTORY (19701215C) 1010200100047 (19800808A) BIB corrections. Converted to REACTION 1010200100048 formalism. 1010200100049 (20000202A) Converted to new date formats, lower case. 1010200100050 ENDBIB 48 0 1010200100051 COMMON 1 3 1010200100052 EN-RSL-FW 1010200100053 MEV 1010200100054 2. 1010200100055 ENDCOMMON 3 0 1010200100056 ENDSUBENT 55 0 1010200199999 SUBENT 10102002 20000202 00001010200200001 BIB 1 1 1010200200002 REACTION (1-H-1(N,TOT),,SIG) 1010200200003 ENDBIB 1 0 1010200200004 NOCOMMON 0 0 1010200200005 DATA 3 8 1010200200006 EN DATA DATA-ERR 1010200200007 MEV MB MB 1010200200008 24.63 385.5 2.3 1010200200009 29.25 315.8 2.6 1010200200010 36.34 247.5 1.8 1010200200011 39.56 223.7 1.7 1010200200012 46.18 185.4 1.6 1010200200013 49.06 167.8 1.5 1010200200014 54.37 151.5 1.2 1010200200015 59.35 133.3 2.2 1010200200016 ENDDATA 10 0 1010200200017 ENDSUBENT 16 0 1010200299999 ENDENTRY 2 0 1010299999999