ENTRY 20067 20070409 21842006700000001 SUBENT 20067001 20070409 21842006700100001 BIB 15 74 2006700100002 INSTITUTE (2SWDFOA) 2006700100003 REFERENCE (J,NP/A,129,305,196905) 2006700100004 AUTHOR (M.Holmberg,J.Hansen) 2006700100005 TITLE -The (N,2N) cross section of be-9 in the energy region 2006700100006 2.0 - 6.4 MeV- 2006700100007 FACILITY (VDG) 5.5 MeV Van de Graaff accelerator 2006700100008 INC-SOURCE (P-T) T(P,N)3He reaction up to 4.6 MeV 2006700100009 thin adsorbed tritium target 2006700100010 (D-D) D(d,N)3He reaction above 4.6 MeV 2006700100011 SAMPLE Be sample in the form of discs 2006700100012 3 cm in diameter and with a length corresponding 2006700100013 to about 1/3 of the total mean free path for neutrons.2006700100014 METHOD (COINC) The two neutrons in the (N,2N) reaction 2006700100015 were detected by a large liquid scintillator by 2006700100016 measuring the correlation time between the pulses due 2006700100017 to the two neutrons. 2006700100018 .Iron collimator, 20 cm square, 1.5 m long 2006700100019 surrounded by lead and paraffin shields. 2006700100020 DETECTOR (SCIN) Gd-loaded liquid scintillator Ne313 in a 2006700100021 cylindrical tank, 50 cm in diameter, 50 cm in length 2006700100022 six 12.7 cm photomultipliers. 2006700100023 .Detector efficiency determined on 85+-2 per-cent by a 2006700100024 98-Cf-252 nu-bar measurement, (nu-bar = 3.772+-0.020).2006700100025 .Time correlation measurements via a coincidence 2006700100026 circuit, on thermal capture pulses, (prompt recoil 2006700100027 pulses are removed). 2006700100028 .Carbon scatterer used to determine zero correlation. 2006700100029 (SCIN ) Plastic scintillator located at the center 2006700100030 of the channel through the scintillator tank during 2006700100031 absolute neutron flux measurement runs. 2006700100032 (LONGC) A long counter at a distance of 5 m from the2006700100033 target was used as a monitor of the relative neutron 2006700100034 flux. 2006700100035 ANALYSIS .The (N,2N) cross section was calculated using the 2006700100036 total cross section of be-9 from the compilation by 2006700100037 Doherty, aeew-m513(1965), in order to account for the 2006700100038 sample thickness. 2006700100039 COMMENT .The (N,2N) cross section increases rapidly above the 2006700100040 threshold at 2.70 MeV for the inelastic neutron 2006700100041 scattering to the 2.43 MeV level of be-9, which sub- 2006700100042 sequently decays by neutron emission. 2006700100043 .There also exists a small (N,2N) cross section in the 2006700100044 energy range 2.0 - 2.7 MeV. 2006700100045 STATUS Data from publication 2006700100046 CORRECTION .Multiple scattering was corrected by use of a MONTE- 2006700100047 CARLO program. 2006700100048 The correction was 14 perc. At 4.2 MeV and the error 2006700100049 was estimated to be less then 2 per-cent. 2006700100050 .Variation of neutron detector efficiency with neutron 2006700100051 energy. The correction was 8 perc. At 6.4 MeV 2006700100052 .Absorption of the (N,2N) neutrons by the (N,alpha) 2006700100053 process in the be sample. The correction was 2 perc. 2006700100054 At 6.4 MeV with an estimated error of 1 per-cent. 2006700100055 .Neutron escape along the axial channel of the 2006700100056 scintillator tank. The correction was (2+-1) perc. 2006700100057 .Spectrum of incident neutrons. The correction was 2006700100058 (3+-1) perc. at 6.40 MeV 2006700100059 .Neutron flux correction (2+-1) per-cent. 2006700100060 ERR-ANALYS .Efficiency of large liquid scintillator for (N,2N) 2006700100061 reaction error 5 perc. 2006700100062 .Efficiency of plastic scintillator error 3 perc. 2006700100063 .Number of counts recorded in plastic scintillator 2006700100064 error 3-4 perc. 2006700100065 .Number of (N,2N) events recorded by the large liquid 2006700100066 scintillator error 2 perc. 2006700100067 .Corrections error 3 perc. 2006700100068 .Total error in the energy region above 2.80 MeV 8 perc2006700100069 .The value is however (not linearly) dependent on the 2006700100070 values of Cf-252 nu-bar and of the be total 2006700100071 cross-section used. 2006700100072 HISTORY (19710428T) From neudada file 2006700100073 (19710908E) 2006700100074 (20070314A) Date and several reaction codes are 2006700100075 corrected - SM 2006700100076 ENDBIB 74 0 2006700100077 COMMON 2 3 2006700100078 ASSUM ASSUM-ERR 2006700100079 PRT/FIS PRT/FIS 2006700100080 3.772 0.020 2006700100081 ENDCOMMON 3 0 2006700100082 ENDSUBENT 81 0 2006700199999 SUBENT 20067002 20070409 21842006700200001 BIB 3 4 2006700200002 REACTION (4-BE-9(N,2N+A)2-HE-4,,SIG) 2006700200003 PART-DET (N) Neutrons 2006700200004 HISTORY (19710428T) From neudada file 2006700200005 (20070314A) Reaction code corrected 2006700200006 ENDBIB 4 0 2006700200007 NOCOMMON 0 0 2006700200008 DATA 3 27 2006700200009 EN DATA DATA-ERR 2006700200010 MEV B B 2006700200011 2.0000E+00 3.0000E-04 2.0000E-03 2006700200012 2.1000E+00 3.0000E-03 2.0000E-03 2006700200013 2.2000E+00 9.0000E-03 2.0000E-03 2006700200014 2.2500E+00 1.1000E-02 2.0000E-03 2006700200015 2.3000E+00 1.6000E-02 2.0000E-03 2006700200016 2.3500E+00 1.5000E-02 2.0000E-03 2006700200017 2.4000E+00 1.6000E-02 2.0000E-03 2006700200018 2.4500E+00 1.9000E-02 3.0000E-03 2006700200019 2.5000E+00 2.4000E-02 3.0000E-03 2006700200020 2.5500E+00 2.3000E-02 3.0000E-03 2006700200021 2.6000E+00 2.7000E-02 3.0000E-03 2006700200022 2.6200E+00 2.9000E-02 3.0000E-03 2006700200023 2.6500E+00 3.2000E-02 3.0000E-03 2006700200024 2.6800E+00 3.5000E-02 4.0000E-03 2006700200025 2.7500E+00 1.5000E-01 2.0000E-02 2006700200026 2.8000E+00 2.0000E-01 2.0000E-02 2006700200027 2.8500E+00 2.5000E-01 2.0000E-02 2006700200028 2.9000E+00 2.7000E-01 3.0000E-02 2006700200029 3.1000E+00 3.7000E-01 3.0000E-02 2006700200030 3.2000E+00 4.2000E-01 3.0000E-02 2006700200031 3.4000E+00 4.7000E-01 3.0000E-02 2006700200032 3.6000E+00 4.8000E-01 4.0000E-02 2006700200033 3.8000E+00 5.1000E-01 4.0000E-02 2006700200034 4.2000E+00 5.1000E-01 4.0000E-02 2006700200035 4.8000E+00 5.4000E-01 4.0000E-02 2006700200036 5.8000E+00 5.8000E-01 5.0000E-02 2006700200037 6.4000E+00 5.8000E-01 5.0000E-02 2006700200038 ENDDATA 29 0 2006700200039 ENDSUBENT 38 0 2006700299999 ENDENTRY 2 0 2006799999999