ENTRY L0270 20210503 L047L027000000001 SUBENT L0270001 20210503 L047L027000100001 BIB 9 21 L027000100002 TITLE Photo-Fission of Uranium and Thorium L027000100003 AUTHOR (R.O.Haxby,W.E.Shoupp,W.E.Stephens,W.H.Wells) L027000100004 REFERENCE (J,PR,59,57,1941) L027000100005 #doi:10.1103/PhysRev.59.57 L027000100006 INSTITUTE (1USAWES) L027000100007 FACILITY (ACCEL,1USAWES) The Westinghouse pressure L027000100008 electrostatic generator. L027000100009 INC-SOURCE Protons interact with CF2 target. The notation L027000100010 19F(p,gamma) is a convenient but inexact designation L027000100011 for the gamma-rays from fluorine bombarded with L027000100012 protons, since it has been shown that most of the L027000100013 high energy rays are emitted from an excited state of L027000100014 16O derived from (20Ne)* by emission of an alpha L027000100015 particle. The energy of the gamma-rays has been L027000100016 measured to be 6.3 MeV and the character of the L027000100017 gamma-rays does not seem to change when the proton L027000100018 energy is varied from 0.33 to 1.36 MeV. L027000100019 DETECTOR (GEMUC,IOCH) L027000100020 COMMENT Compiler's comment: There is a 6.0484 MeV in the L027000100021 ground-state band of 16O. L027000100022 HISTORY (20210503C) BP L027000100023 ENDBIB 21 0 L027000100024 COMMON 1 3 L027000100025 EN-APRX L027000100026 MEV L027000100027 6.3 L027000100028 ENDCOMMON 3 0 L027000100029 ENDSUBENT 28 0 L027000199999 SUBENT L0270002 20210503 L047L027000200001 BIB 6 29 L027000200002 REACTION (92-U-238(G,F),,SIG) L027000200003 SAMPLE The first film was gray, and was assumed to be U308, L027000200004 while the second was black, assumed to be UO2. The L027000200005 weight of the first film was 4.06 mg, giving N = 0.87x L027000200006 10**19. The second, black, film (UO2) weighed 5.75 mg, L027000200007 giving 1.27X10**19 atoms from the weight. L027000200008 METHOD (REC) The cross section for the photo-fission process L027000200009 was measured by using a uranium film thin enough so L027000200010 that every fission process could be observed in the L027000200011 ionization chamber. Since each fission produces a L027000200012 pair of recoil atoms having roughly the same mass, L027000200013 one of the particles will be in a direction to be L027000200014 recorded by the ionization, while the other will be L027000200015 absorbed in the backing plate on which the uranium is L027000200016 deposited. The evaporated films we used contained L027000200017 approximately 1 mg/cm2, which is roughly 1/4 cm air L027000200018 equivalent in stopping power. Fifteen runs were taken L027000200019 in the determination of the fission rate per proton L027000200020 current. Two uranium films were used, the proton L027000200021 energy and current were varied as well as the L027000200022 distance of the uranium to the target. In a sample L027000200023 run, 41 fissions were observed in 295 seconds from a L027000200024 uranium film containing 1.22x10**19 atoms placed so L027000200025 that 1/4*pi*r**2 was 0.0134 cm2 when the CaF2 target L027000200026 was bombarded with 0.91 microa of 3.0-MeV protons. L027000200027 ANALYSIS The mean value of these fifteen determinations of the L027000200028 uranium cross section. L027000200029 ERR-ANALYS (DATA-ERR) Probable errors. L027000200030 STATUS (TABLE) page 61. L027000200031 ENDBIB 29 0 L027000200032 NOCOMMON 0 0 L027000200033 DATA 2 1 L027000200034 DATA DATA-ERR L027000200035 MB PER-CENT L027000200036 3.47 30.0 L027000200037 ENDDATA 3 0 L027000200038 ENDSUBENT 37 0 L027000299999 SUBENT L0270003 20210503 L047L027000300001 BIB 5 16 L027000300002 REACTION ((92-U-238(G,F),,SIG)/(90-TH-232(G,F),,SIG)) L027000300003 SAMPLE Thick target of uranium and thorium. The thorium used L027000300004 was spectroscopically free of uranium, and the L027000300005 uranium had less than a few percent of thorium L027000300006 contamination. L027000300007 METHOD We were unable to get such a good check in the L027000300008 analogous procedure for a thin evaporated film of L027000300009 thorium. Therefore, the cross section for thorium was L027000300010 obtained by comparing the fission yields from thick L027000300011 targets of uranium and thorium. In each case the same L027000300012 exposed area of freshly sandpapered metal was used. L027000300013 This is the average of several runs at different L027000300014 proton energies. L027000300015 ERR-ANALYS (ERR-S) The uncertainty arises mainly from the L027000300016 statistical fluctuations involved. L027000300017 STATUS (TABLE) page 60. L027000300018 ENDBIB 16 0 L027000300019 NOCOMMON 0 0 L027000300020 DATA 2 1 L027000300021 DATA ERR-S L027000300022 NO-DIM NO-DIM L027000300023 2.0 0.1 L027000300024 ENDDATA 3 0 L027000300025 ENDSUBENT 24 0 L027000399999 SUBENT L0270004 20210503 L047L027000400001 BIB 4 7 L027000400002 REACTION (90-TH-232(G,F),,SIG) L027000400003 ANALYSIS Coupled uranium cross section with the result already L027000400004 cited for the ratio of sigma U to sigma Th. L027000400005 ERR-ANALYS (DATA-ERR) Probable errors. L027000400006 STATUS (DEP,L0270002) L027000400007 (DEP,L0270003) L027000400008 (TABLE) page 61. L027000400009 ENDBIB 7 0 L027000400010 NOCOMMON 0 0 L027000400011 DATA 2 1 L027000400012 DATA DATA-ERR L027000400013 MB PER-CENT L027000400014 1.73 30.0 L027000400015 ENDDATA 3 0 L027000400016 ENDSUBENT 15 0 L027000499999 ENDENTRY 4 0 L027099999999