ENTRY 21150 19800512 00002115000000001 SUBENT 21150001 19800512 00002115000100001 BIB 9 16 2115000100002 INSTITUTE (2UK NPL) NATIONAL PHYSICAL LABORATORY, U.K. 2115000100003 (2UK ALD) 24 KEV EXPERIMENT CARRIED OUT AT AWRE 2115000100004 ALDERMASTON. 2115000100005 (2UK HAR) EXPERIMENT AT THERMAL ENERGY CARRIED OUT 2115000100006 AT AERE HARWELL. 2115000100007 REFERENCE (J,NP,71,417,6509) 2115000100008 (C,65ANTWERP,552,6507) ABSTRACT. 2115000100009 AUTHOR (J.C.ROBERTSON) 2115000100010 TITLE -THE RADIATIVE CAPTURE CROSS SECTION OF IODINE AT 2115000100011 24 KEV AND THERMAL ENERGY- 2115000100012 FACILITY (REAC ) GLEEP REACTOR USED AT AERE HARWELL. 2115000100013 METHOD (ACTIV) ACTIVATION. 2115000100014 DETECTOR (CSICR) CSI SCINTILLATOR, ALSO USED AS SAMPLE. 2115000100015 STATUS .DATA TABLES IN PUBLICATION. 2115000100016 HISTORY (790503C) 2115000100017 (791206E) 2115000100018 ENDBIB 16 0 2115000100019 NOCOMMON 0 0 2115000100020 ENDSUBENT 19 0 2115000199999 SUBENT 21150002 19791206 00002115000200001 BIB 8 39 2115000200002 REACTION (53-I-127(N,G)53-I-128,,SIG) 2115000200003 INC-SOURCE (PHOTO) SB-BE PHOTONEUTRON SOURCE CALIBRATED ABSOLUTELY2115000200004 IN A MANGANESE BATH TO +-0.5 PC. HALF-LIFE OF S2115000200005 124 TAKEN TO BE 60.2+-0.03 D TO COMPUTE CHANGES2115000200006 OF SOURCE STRENGTH WITH TIME. SOURCE STRENGTH A2115000200007 THE TIME OF IRRADIATION WAS 7.37X10**6 N/SEC. 2115000200008 SAMPLE .CSI CRYSTAL OF DIAMETER 2.54 CM AND THICKNESS 0.38 CM.2115000200009 ANALYSIS .CROSS SECTION EXTRACTED BY FITTING A STRAIGHT LINE TO 2115000200010 THE VARIATION OF I-128 ACTIVITY WITH INVERSE SQUARE OF2115000200011 THE DISTANCE FROM THE SOURCE. 2115000200012 DECAY-DATA (51-SB-124,60.2D,B-) FROM LITERATURE. 2115000200013 STATUS .TABLE 2. 2115000200014 CORRECTION .CORRECTIONS MADE FOR- 2115000200015 1.EFFICIENCY OF BETA COUNTING- I.E. LOSS OF BETAS 2115000200016 EMITTED BELOW THE BIAS ENERGY AND THOSE HIGH ENERG2115000200017 BETAS WHICH LOSE LESS THAN THE BIAS ENERGY BEFORE 2115000200018 ESCAPING FROM THE CRYSTAL- TOTAL B EFFICIENCY 90.92115000200019 IN ADDITION THERE IS AN UNDETECTED ELECTRON CAPTUR2115000200020 BRANCH OF THE I-128 DECAY OF 6.4+-0.6 PC. 2115000200021 TOTAL DETECTION EFFICIENCY=85.1 PC FOR ALL DECAYS.2115000200022 2.ENERGY SPREAD IN THE SOURCE DUE TO KINETICS, COMPT2115000200023 SCATTERING AND IMPURITIES MEAN THAT THE MEASURED X2115000200024 DIFFERS FROM THE 24 KEV XSEC. 2115000200025 SIGMA(24 KEV)/SIGMA(MEASURED) = 0.992 FOR KINETIC 2115000200026 SPREAD ALONE- THE OTHER EFFECTS WERE NEGLECTED. 2115000200027 3.INCREASE IN AVERAGE PATH LENGTH THROUGH THE SAMPLE2115000200028 DUE TO SCATTERING WHICH RAISES THE PROBABILITY OF 2115000200029 ABSORPTION. CORRECTION FACTOR IS 0.8+-0.1 PC. 2115000200030 4.RESONANCE SELF SHIELDING IN INFINITELY DILUTE 2115000200031 APPROXIMATION. CORRECTION FACTOR OF 1.3 PC USED. 2115000200032 ERR-ANALYS .TOTAL ERROR OF 3.2 PC COMPOSED OF A LINEAR ADDITION OF2115000200033 1.A RANDOM ERROR OF 1.25 PC FROM THE INVERSE SQUARE 2115000200034 LAW FIT. 2115000200035 2.A SYSTEMATIC ERROR OF 1.9 PC DERIVED FROM, 2115000200036 THE NEUTRON STRENGTH OF THE SOURCE...0.5 PC 2115000200037 ERROR IN BETA EFFICIENCY.............1.5 PC 2115000200038 THE SOURCE ENERGY SPECTRUM...........1.0 PC 2115000200039 THE MULTIPLE SCATTERING CORRECTION...0.2 PC 2115000200040 RESONANCE SELF SHIELDING.............0.2 PC 2115000200041 ENDBIB 39 0 2115000200042 NOCOMMON 0 0 2115000200043 DATA 3 1 2115000200044 EN DATA DATA-ERR 2115000200045 KEV MB MB 2115000200046 2.4000E+01 8.3200E+02 2.6000E+01 2115000200047 ENDDATA 3 0 2115000200048 ENDSUBENT 47 0 2115000299999 SUBENT 21150003 19800512 00002115000300001 BIB 8 32 2115000300002 REACTION (53-I-127(N,G)53-I-128,,SIG,,MXW) 2115000300003 INC-SOURCE (REAC ) GLEEP REACTOR AT AERE USING FLUX VALUE AS 2115000300004 CALIBRATED BY AXTON- REACTOR SCI.TECH.,17, 2115000300005 (1963),125. 2115000300006 INC-SPECT WESTCOTT EPITHERMAL FLUX PARAMETER, R = 0.049. 2115000300007 EFFECTIVE NEUTRON TEMPERATURE = 80+-10 DEG C. 2115000300008 .THOUGH THE REACTOR FLUX HAS AN EPITHERMAL COMPONENT 2115000300009 ITS EFFECT WAS ELIMINATED BY PERFORMING THE EXPERIMENT2115000300010 WITH AND WITHOUT A CADMIUM CASE ROUND THE SAMPLE TO 2115000300011 ABSORB THE THERMAL NEUTRONS. 2115000300012 SAMPLE .CSI CRYSTAL OF DIAMETER 2.54 CM AND THICKNESS 0.38 CM 2115000300013 PLACED IN AN AIR CAVITY IN A LARGE GRAPHITE BOAT IN 2115000300014 THE REACTOR. 2115000300015 COMMENT .THE THERMAL MEASUREMENT WAS MADE TO SHOW ANY GROSS 2115000300016 ERRORS IN THE METHOD OF MEASURING THE 24 KEV CROSS 2115000300017 SECTION AND THE AUTHOR MAKES NO CLAIM THAT THIS IS 2115000300018 THE BEST WAY OF MEASURING THE THERMAL CROSS SECTION. 2115000300019 STATUS .TABLE 3. 2115000300020 CORRECTION .THE FOLLOWING CORRECTIONS WERE MADE- 2115000300021 1.ATTENUATION OF EPITHERMAL NEUTRON IN THE CADMIUM. 2115000300022 2.RESONANCE SELF SHIELDING, CORRECTION = 15 PC+-1.5 2115000300023 3.FLUX DEPRESSION IN THE AIR CAVITY CONTAINING THE 2115000300024 SAMPLE, CORRECTION = 1.5+-1 PC. 2115000300025 ERR-ANALYS .TOTAL ERROR OF 3.2 PC IS A LINEAR ADDITION OF- 2115000300026 1.A RANDOM ERROR OF 0.6 PC FROM, 2115000300027 COUNTING STATISTICS..................0.25 PC 2115000300028 TIMING ERRORS........................0.50 PC 2115000300029 2.A SYSTEMATIC ERROR OF 2.6 PC FROM, 2115000300030 BETA EFFICIENCY......................1.5 PC 2115000300031 ERROR IN FLUX DEPRESSION CORRECTION..1.0 PC 2115000300032 ERROR IN SELF SHIELDING CORRECTION...1.5 PC 2115000300033 ERROR IN FLUX MEASUREMENT............1.5 PC 2115000300034 ENDBIB 32 0 2115000300035 NOCOMMON 0 0 2115000300036 DATA 3 1 2115000300037 EN-DUMMY DATA DATA-ERR 2115000300038 EV B B 2115000300039 2.5300E-02 6.1700E+00 2.0000E-01 2115000300040 ENDDATA 3 0 2115000300041 ENDSUBENT 40 0 2115000399999 ENDENTRY 3 0 2115099999999