ENTRY 32694 20120216 31573269400000001 SUBENT 32694001 20120216 31573269400100001 BIB 16 75 3269400100002 TITLE Measurement of cross sections for the 10B(n,a)7Li 3269400100003 reaction at 4.0 and 5.0 MeV using an asymmetrical 3269400100004 twin gridded ionization chamber 3269400100005 AUTHOR (Zhang Guohui,Liu Xiang,Liu Jiaming,Xue Zhihua,Wu Hao, 3269400100006 Chen Jinxiang) 3269400100007 INSTITUTE (3CPRBJG) 3269400100008 REFERENCE (J,CPL,28,(8),082801,2011) 3269400100009 #doi:10.1088/0256-307X/28/8/082801 3269400100010 REL-REF (N,31617002,Guohui Zhang+,J,ARI,66,1427,2008) 3269400100011 Another measurement of the same reaction 3269400100012 FACILITY (VDG,3CPRBJG) 4.5MV Van de Graaff accelerator were 3269400100013 used. 3269400100014 INC-SOURCE (D-D) The length and diameter of the deuterium gas 3269400100015 cell are 2.0 cm and 0.9 cm, respectively. The gas 3269400100016 cell was separated from the vacuum tube by a 3269400100017 molybdenum foil 5 mu-m in thickness. The deuterium 3269400100018 gas pressure range was about 3.1-2.9 atm. 3269400100019 DETECTOR (IOCH)A twin gridded ionization chamber was used as 3269400100020 the charged particle detector with forward and 3269400100021 backward asymmetrical sections. It has the advantages 3269400100022 of high detection efficiency (about 100%), large 3269400100023 detection solid angle (about 4Pi). The shape of the 3269400100024 chamber is cylindrical, with diameter 28.2 cm and 3269400100025 height 27.2 cm. The shape of electrodes is 3269400100026 rectangular and include one common cathode, two grids, 3269400100027 two anodes and two shields. For the forward section, 3269400100028 the distances from cathode to grid, grid to anode, 3269400100029 and anode to shield were 44.0, 22.0 and 11.0 mm, 3269400100030 respectively. For the backward section, they were 3269400100031 18.0, 9.0 and 11.0 mm, respectively. The working gas 3269400100032 of the ionization chamber was a Kr+2.89%CO2 mixture 3269400100033 at pressure of 1.10 atm. High voltages for the 3269400100034 cathode, grids and anodes were -1100, 0 and +900 V, 3269400100035 respectively. 3269400100036 (BF3)A BF3 long counter was used for neutron flux 3269400100037 monitoring and normalization. The axis of the BF3 3269400100038 long counter and the normal line of the electrodes of 3269400100039 the gridded ionization chamber were at 0 degree to 3269400100040 the beam line. The distance from the cathode of the 3269400100041 ionization chamber to the center of the neutron 3269400100042 source was 15.9 cm, and that from the front side of 3269400100043 the moderator of the BF3 long counter to the neutron 3269400100044 source was about 2.40 m. 3269400100045 SAMPLE (5-B-10,ENR=0.940) The thicknesses of the forward and 3269400100046 backward samples are 21.3 and 23.0 mu-g/cm2, 3269400100047 respectively, and the diameter of both 10B samples is 3269400100048 42.0 mm. Each 10B sample was vacuum evaporated on a 3269400100049 circular tantalum backing 48.0 mm in diameter and 100 3269400100050 um in thickness. The mass and the diameter of the 238U 3269400100051 sample were 7.85+-0.10 mg and 4.50 cm, and the 3269400100052 enrichment of the 238U is 99.999%. 3269400100053 PART-DET (A,FF) Alpha particles and fission fragments. 3269400100054 ERR-ANALYS (ERR-1,5.,8.) Uncertainty of the background 3269400100055 subtraction for alpha counts 3269400100056 (ERR-2,,,U) 238U fission counts 3269400100057 (ERR-3) BF3 normalization in the background subtraction3269400100058 (ERR-4,1.,2.,U) Statistics uncertainty of alpha counts 3269400100059 (ERR-5) Number of atoms in the 10B samples 3269400100060 (ERR-6) Number of atoms in the 238U samples 3269400100061 (MONIT-ERR) 238U fission cross section 3269400100062 MONITOR (92-U-238(N,F),,SIG) 3269400100063 MONIT-REF (,,3,ENDF/B-VII.0,9237,2006) 3269400100064 COMMENT The cross section values of monitor reaction were 3269400100065 provided and confirmed by author. 3269400100066 This paper is first time to report the information of 3269400100067 Leaking alpha. Usually, measure the Forward and 3269400100068 Backward alpha and sum of those two part contribution 3269400100069 as total (n,a) reaction. However, especially for the 3269400100070 target is light nuclei, the contribution of Leaking 3269400100071 alpha couldn't be ignored. As an example, the 3269400100072 contribution of Leaking alpha is 15.6% at 4 MeV in this3269400100073 measurement. 3269400100074 STATUS (TABLE)Data taken from Table 2 of J,CPL,28,(8),082801, 3269400100075 2011. 3269400100076 HISTORY (20120216C)Compiled by Jimin WANG(CNDC) 3269400100077 ENDBIB 75 0 3269400100078 COMMON 5 3 3269400100079 ERR-2 ERR-3 ERR-5 ERR-6 MONIT-ERR 3269400100080 PER-CENT PER-CENT PER-CENT PER-CENT PER-CENT 3269400100081 2.5 2.5 2.5 1.3 1.0 3269400100082 ENDCOMMON 3 0 3269400100083 ENDSUBENT 82 0 3269400199999 SUBENT 32694002 20120216 31573269400200001 BIB 1 1 3269400200002 REACTION (5-B-10(N,A)3-LI-7,,SIG) 3269400200003 ENDBIB 1 0 3269400200004 NOCOMMON 0 0 3269400200005 DATA 5 2 3269400200006 EN EN-RSL DATA ERR-T MONIT 3269400200007 MEV MEV MB MB MB 3269400200008 4.0 0.16 243. 13. 554.40 3269400200009 5.0 0.23 144. 9. 546.71 3269400200010 ENDDATA 4 0 3269400200011 ENDSUBENT 10 0 3269400299999 ENDENTRY 2 0 3269499999999