ENTRY 14724 20211211 14951472400000001 SUBENT 14724001 20211211 14951472400100001 BIB 10 34 1472400100002 TITLE A comparison of boron and 25 fission cross-sections 1472400100003 for neutrons of energies from thermal to 3 MeV 1472400100004 AUTHOR (C.L.Bailey,J.M.Blair,W.C.Bright,D.H.Frisch,K.Greisen, 1472400100005 A.O.Hansen,J.H.Hush,E.J.Konopinski,R.Krohn, 1472400100006 J.L.McKibben,R.Perry,H.R.Richards, R.F.Taschek, 1472400100007 C.H.Turner,J.H.Williams) 1472400100008 REFERENCE (R,LA-46,1944) 1472400100009 INSTITUTE (1USALAS) 1472400100010 FACILITY (VDG,1USALAS) Electrostatic generator. 1472400100011 INC-SOURCE (P-LI7) Neutrons were obtained from a thick lithium 1472400100012 target bombarded by protons from the short 1472400100013 electrostatic generator in W. This meant maximum 1472400100014 energy of the neutron emitted at 0 degree was about 1472400100015 170 keV and emitted at 90 degree about 25 keV. The 1472400100016 average energy including neutrons emitted at all 1472400100017 angles from a thick target was computed to be about 5 1472400100018 keV. The target was surrounded by a paraffin sphere 1472400100019 having a radius of 3.5 cm, or alternatively by a 1472400100020 carbon sphere having a radius of 12 cm. 1472400100021 SAMPLE The detector samples consisted of thin films of boron 1472400100022 and 235U on platinum foils. The 235U foils had a 1472400100023 density of less than 40 micrograms of 235U per cm2, 1472400100024 and the boron films had a considerably lower density 1472400100025 so there could be no appreciable shielding due to 1472400100026 absorption of neutrons in the foils. 1472400100027 METHOD The experiment, in its simplest form, again consists 1472400100028 of comparing the counting rates of the fission in the 1472400100029 235U chamber and of the alpha-particles in a boron 1472400100030 chamber. 1472400100031 DETECTOR (IOCH,BF3) Target foils were mounted on opposite 1472400100032 sides of common electrode in the double ionization 1472400100033 chamber. Gas filled chamber with BF3 and a 25 fission 1472400100034 chamber. 1472400100035 HISTORY (20211211C) BP 1472400100036 ENDBIB 34 0 1472400100037 NOCOMMON 0 0 1472400100038 ENDSUBENT 37 0 1472400199999 SUBENT 14724002 20211211 14951472400200001 BIB 4 8 1472400200002 REACTION ((5-B-10(N,A)3-LI-7,,SIG)/(92-U-235(N,F),,SIG)) 1472400200003 METHOD Direct comparison of sigma B/ sigma 235U to that at 1472400200004 thermal energies using thin film of Boron and 235U in 1472400200005 the Comparison chamber. 1472400200006 MONITOR ((5-B-10(N,A)3-LI-7,,SIG)/(92-U-235(N,F),,SIG)) Data 1472400200007 normalized to sigma 10B / sigma 25 = 6.0 for thermal 1472400200008 energies. 1472400200009 STATUS (CURVE) Fig. 6, page 30. 1472400200010 ENDBIB 8 0 1472400200011 COMMON 2 3 1472400200012 MONIT EN-NRM 1472400200013 NO-DIM EV 1472400200014 6.0 0.0253 1472400200015 ENDCOMMON 3 0 1472400200016 DATA 2 5 1472400200017 EN DATA 1472400200018 MEV NO-DIM 1472400200019 0.032 1.673 1472400200020 0.056 1.587 1472400200021 0.106 1.497 1472400200022 0.224 1.428 1472400200023 0.405 1.170 1472400200024 ENDDATA 7 0 1472400200025 ENDSUBENT 24 0 1472400299999 SUBENT 14724003 20211211 14951472400300001 BIB 3 4 1472400300002 REACTION ((5-B-10(N,A)3-LI-7,,SIG)/(92-U-235(N,F),,SIG)) 1472400300003 METHOD Relative values taken with gas chamber containing 1472400300004 1 atmosphere of BF3. 1472400300005 STATUS (CURVE) Fig. 6, page 30. 1472400300006 ENDBIB 4 0 1472400300007 NOCOMMON 0 0 1472400300008 DATA 2 11 1472400300009 EN DATA 1472400300010 MEV NO-DIM 1472400300011 0.136 1.402 1472400300012 0.348 1.322 1472400300013 0.445 1.059 1472400300014 0.531 0.829 1472400300015 0.581 0.652 1472400300016 0.726 0.567 1472400300017 0.802 0.523 1472400300018 0.918 0.466 1472400300019 1.321 0.416 1472400300020 1.439 0.409 1472400300021 1.691 0.547 1472400300022 ENDDATA 13 0 1472400300023 ENDSUBENT 22 0 1472400399999 SUBENT 14724004 20211211 14951472400400001 BIB 3 4 1472400400002 REACTION ((5-B-10(N,A)3-LI-7,,SIG)/(92-U-235(N,F),,SIG)) 1472400400003 METHOD Relative values taken with gas chamber containing 1472400400004 3#BF3 60#(Gauge) of Argon. 1472400400005 STATUS (CURVE) Fig. 6, page 30. 1472400400006 ENDBIB 4 0 1472400400007 NOCOMMON 0 0 1472400400008 DATA 2 6 1472400400009 EN DATA 1472400400010 MEV NO-DIM 1472400400011 0.058 1.727 1472400400012 0.108 1.604 1472400400013 0.392 1.087 1472400400014 0.565 0.751 1472400400015 0.916 0.412 1472400400016 1.321 0.383 1472400400017 ENDDATA 8 0 1472400400018 ENDSUBENT 17 0 1472400499999 SUBENT 14724005 20211211 14951472400500001 BIB 3 5 1472400500002 REACTION ((5-B-10(N,A)3-LI-7,,SIG)/(92-U-235(N,F),,SIG)) 1472400500003 METHOD Relative values taken with gas chamber containing 1472400500004 3#BF3 60#(Gauge) of Argon at 90 degrees to the 1472400500005 direction of the proton beam. 1472400500006 STATUS (CURVE) Fig. 6, page 30. 1472400500007 ENDBIB 5 0 1472400500008 NOCOMMON 0 0 1472400500009 DATA 2 6 1472400500010 EN DATA 1472400500011 MEV NO-DIM 1472400500012 0.016 1.825 1472400500013 0.058 1.653 1472400500014 0.106 1.571 1472400500015 0.154 1.411 1472400500016 0.295 1.441 1472400500017 0.396 1.223 1472400500018 ENDDATA 8 0 1472400500019 ENDSUBENT 18 0 1472400599999 SUBENT 14724006 20211211 14951472400600001 BIB 5 10 1472400600002 REACTION (5-B-10(N,A)3-LI-7,,SIG) 1472400600003 METHOD Filling the neutron chamber with an accurately 1472400600004 measured amount of BF3 and comparing its geometry 1472400600005 with the source and its counting rate to that of the 1472400600006 fission sample which was used in the measurements of 1472400600007 the 235U cross section made in Wisconsin. 1472400600008 MONITOR (92-U-235(N,F),,SIG) 1472400600009 MONIT-REF ((MONIT)14666002,A.O.Hanson,R,CF-618,1943) 235U cross 1472400600010 section measurement in Wisconsin. 1472400600011 STATUS (TABLE) page 21. 1472400600012 ENDBIB 10 0 1472400600013 NOCOMMON 0 0 1472400600014 DATA 3 1 1472400600015 EN DATA MONIT 1472400600016 MEV B B 1472400600017 0.58 1.27 1.7 1472400600018 ENDDATA 3 0 1472400600019 ENDSUBENT 18 0 1472400699999 ENDENTRY 6 0 1472499999999