ENTRY 20785 20080122 21932078500000001 SUBENT 20785001 20080122 21932078500100001 BIB 11 40 2078500100002 INSTITUTE (2UK HAR) 2078500100003 REFERENCE (C,77KIEV,3,3,19770418) Comments, curves and fission 2078500100004 width values are given. (In English) 2078500100005 (W,GAYTHER,19780923) Cross-section values given on 2078500100006 sheets. 2078500100007 AUTHOR (D.B.Gayther, B.W.Thomas) 2078500100008 TITLE -Measurement of the neutron capture and fission 2078500100009 cross-sections of Am-241 - 2078500100010 REL-REF (N,,M.S.Coates+,C,77KIEV,4,139,1977) Facility details. 2078500100011 (In English) 2078500100012 FACILITY (LINAC) Harwell 45 MeV electron accelerator, running at2078500100013 repetition frequency of 192 MHz. 2078500100014 INC-SOURCE (PHOTO) Neutron booster target of the Harwell LINAC. 2078500100015 SAMPLE -Am-241 sample was approximately 12 grams of AmO2 2078500100016 giving an N-value for the Am-241 of 1.32*10**-3 2078500100017 atoms/barn. 2078500100018 -It was canned in nickel and aluminum each having a 2078500100019 total thickness of 0.4 mm. 2078500100020 -An identical empty can was used to evaluate the 2078500100021 contribution of the canning material to the 2078500100022 background. 2078500100023 -The major impurities were plutonium isotopes (1.5 % 2078500100024 by weight) of which about half was Pu-239. 2078500100025 -Samples were mounted in a double sleeve of boron and 2078500100026 lead to reduce the effects of scattered neutrons and 2078500100027 soft gamma-rays at the detector. 2078500100028 - U-235 sample of 3.8E-03 atoms/barn for fission 2078500100029 measurement only. 2078500100030 COMMENT Comparison with other data. 2078500100031 STATUS (APRVD) Data taken from 77KIEV and private 2078500100032 communication, 1978-09-23. 2078500100033 HISTORY (19780926C) 2078500100034 (19781213E) 2078500100035 (19801204A) G.C., MONITOR reaction strings corrected, 2078500100036 error analyses changed. 2078500100037 (19801218E) 2078500100038 (20080122A) M.M. BIB and COMMON information was added. 2078500100039 SUBENT .002 REACTION code was changed from "(N,G)" 2078500100040 into "(N,ABS)". MONITORs values were corrected in 2078500100041 according to data from text of 1st reference. 2078500100042 ENDBIB 40 0 2078500100043 NOCOMMON 0 0 2078500100044 ENDSUBENT 43 0 2078500199999 SUBENT 20785002 20080122 21932078500200001 BIB 10 59 2078500200002 REACTION (95-AM-241(N,ABS),,SIG,,AV) Average neutron 2078500200003 absorption cross-section (predominantly capture). 2078500200004 METHOD (TOF) Gamma-yield measurements were carried out for 2078500200005 both Am-241 and the blank sample holder with a 2078500200006 scintillator situated at the 100 meter flight path. 2078500200007 -The accelerator pulse width was 0.5 micro-sec and 2078500200008 the nominal resolution of 5.8 nano-sec/meter. 2078500200009 -A 6 mm lead sleeve was placed around the sample to 2078500200010 reduce the soft gamma-ray pule up. 2078500200011 -A bias of 3 MeV was imposed to the detector. 2078500200012 -The detector was only used in the coincidence mode. 2078500200013 -Time-of-flight data were accumulated for a fixed 2078500200014 pulse-height window of 3 MeV to 7 MeV using a digital 2078500200015 time analyzer width 1/4 micro-sec timing channel and 2078500200016 the ability to accept several events per accelerator 2078500200017 cycle. 2078500200018 -The shape of the absorption c.s. was determined 2078500200019 using the same sample in the range 100 eV to 500 keV. 2078500200020 In this case capture gamma-ray events were detected 2078500200021 with a large liquid scintillator. 2078500200022 "Black resonance" technique with aluminum and 2078500200023 manganese filters - to determine the time-independent 2078500200024 component of background. Shape and magnitude of this 2078500200025 background was found to be almost identical with yield2078500200026 obtained for blank sample holder in region < 150 keV. 2078500200027 DETECTOR (STANK) 230 l Large liquid scintillator. 2078500200028 Detector efficiency is the same for capture and 2078500200029 fission events. 2078500200030 MONITOR (92-U-235(N,G)92-U-236,,SIG,,AV) 2078500200031 (3-LI-6(N,T)2-HE-4,,SIG) 2078500200032 Shape of incident neutron spectrum was determined by 2078500200033 comparison with Li-6(n,a) cross-section below 30 keV 2078500200034 and U-235(n,f) cross-section at higher energies. 2078500200035 ((MONIT)95-AM-241(N,ABS),,SIG,,AV) 2078500200036 Cross-section was normalized in energy range form 1keV2078500200037 to 2keV to value of 9.48b from MONIT-REF. 2078500200038 PART-DET (G) Capture gammas. 2078500200039 MONIT-REF (10767002,L.W.Weston+,C,75WASH,229,1975) 2078500200040 STATUS (APRVD) Data taken from 77KIEV and private 2078500200041 communication, 1978-09-23. 2078500200042 HISTORY (19780926C) 2078500200043 (19781213E) 2078500200044 (19801204A) G.C., MONITOR reaction strings corrected, 2078500200045 error analysis changed. 2078500200046 (19801218E) 2078500200047 (19860808A)HH REACTION/MONITOR string corrected 2078500200048 (19860807E) 2078500200049 CORRECTION -For time-dependent and constant background. 2078500200050 -For sample thickness effects less 3%. 2078500200051 -For multiple scattering and self shielding effects 2078500200052 from 4.5 % at 100 eV to 12% at 500keV. 2078500200053 -For detector efficiency. 2078500200054 ERR-ANALYS (ERR-S) Statistical error corresponding to one standard2078500200055 deviation (12%). 2078500200056 This error does not include any uncertainty in the 2078500200057 assumed average cross-section in the 1 to 2 keV 2078500200058 energy interval where the data were normalized. 2078500200059 (ERR-1)Uncertainty in determining the shape of incident2078500200060 neutron flux less 3%. 2078500200061 ENDBIB 59 0 2078500200062 COMMON 4 3 2078500200063 EN-NRM-MIN EN-NRM-MAX MONIT ERR-1 2078500200064 KEV KEV B PER-CENT 2078500200065 1. 2. 9.48 3. 2078500200066 ENDCOMMON 3 0 2078500200067 DATA 4 39 2078500200068 EN-MIN EN-MAX DATA ERR-S 2078500200069 KEV KEV B B 2078500200070 1.0000E-01 1.5000E-01 3.8100E+01 4.6000E+00 2078500200071 1.5000E-01 2.0000E-01 2.3290E+01 2.8000E+00 2078500200072 2.0000E-01 2.5000E-01 2.0410E+01 2.4000E+00 2078500200073 2.5000E-01 3.0000E-01 2.5330E+01 3.0000E+00 2078500200074 3.0000E-01 4.0000E-01 2.0380E+01 2.4000E+00 2078500200075 4.0000E-01 5.0000E-01 1.8590E+01 2.2000E+00 2078500200076 5.0000E-01 6.0000E-01 1.4410E+01 1.7000E+00 2078500200077 6.0000E-01 7.0000E-01 1.5500E+01 1.9000E+00 2078500200078 7.0000E-01 8.0000E-01 1.2180E+01 1.5000E+00 2078500200079 8.0000E-01 9.0000E-01 1.1510E+01 1.4000E+00 2078500200080 9.0000E-01 1.0000E+00 9.9200E+00 1.2000E+00 2078500200081 1.0000E+00 1.5000E+00 1.0590E+01 1.3000E+00 2078500200082 1.5000E+00 2.0000E+00 8.3700E+00 1.0000E+00 2078500200083 2.0000E+00 2.5000E+00 7.7800E+00 9.3000E-01 2078500200084 2.5000E+00 3.0000E+00 6.5300E+00 7.8000E-01 2078500200085 3.0000E+00 4.0000E+00 5.9900E+00 7.2000E-01 2078500200086 4.0000E+00 5.0000E+00 5.2100E+00 6.3000E-01 2078500200087 5.0000E+00 6.0000E+00 5.1600E+00 6.2000E-01 2078500200088 6.0000E+00 7.0000E+00 4.4100E+00 5.3000E-01 2078500200089 7.0000E+00 8.0000E+00 4.1600E+00 5.0000E-01 2078500200090 8.0000E+00 9.0000E+00 3.6300E+00 4.4000E-01 2078500200091 9.0000E+00 1.0000E+01 3.8200E+00 4.6000E-01 2078500200092 1.0000E+01 1.5000E+01 3.3600E+00 4.0000E-01 2078500200093 1.5000E+01 2.0000E+01 3.2000E+00 3.8000E-01 2078500200094 2.0000E+01 2.5000E+01 2.8400E+00 3.4000E-01 2078500200095 2.5000E+01 3.0000E+01 2.6400E+00 3.2000E-01 2078500200096 3.0000E+01 4.0000E+01 2.5000E+00 3.0000E-01 2078500200097 4.0000E+01 5.0000E+01 2.2600E+00 2.7000E-01 2078500200098 5.0000E+01 6.0000E+01 2.0000E+00 2.4000E-01 2078500200099 6.0000E+01 7.0000E+01 1.8500E+00 2.2000E-01 2078500200100 7.0000E+01 8.0000E+01 1.8100E+00 2.2000E-01 2078500200101 8.0000E+01 9.0000E+01 1.7100E+00 2.1000E-01 2078500200102 9.0000E+01 1.0000E+02 1.7000E+00 2.0000E-01 2078500200103 1.0000E+02 1.5000E+02 1.3700E+00 1.6000E-01 2078500200104 1.5000E+02 2.0000E+02 1.1900E+00 1.4000E-01 2078500200105 2.0000E+02 2.5000E+02 1.0600E+00 1.3000E-01 2078500200106 2.5000E+02 3.0000E+02 9.8000E-01 1.2000E-01 2078500200107 3.0000E+02 4.0000E+02 8.9000E-01 1.1000E-01 2078500200108 4.0000E+02 5.0000E+02 9.2000E-01 1.1000E-01 2078500200109 ENDDATA 41 0 2078500200110 ENDSUBENT 109 0 2078500299999 SUBENT 20785003 20080122 21932078500300001 BIB 12 106 2078500300002 REACTION (95-AM-241(N,F),,SIG,,AV) 2078500300003 METHOD (TOF) Fission yields measurements were made for the 2078500300004 Am-241 and U-235 samples, using a 13 m flight path. 2078500300005 (PSD) Pulse shape discrimination against gammas 2078500300006 -The U-235 measurements were used to establish an 2078500300007 absolute scale for the Am-241 fission cross-section. 2078500300008 -In each case the electron pulse length was 150 nsec, 2078500300009 giving a nominal resolution of nsec/meter. 2078500300010 -Fission events were detected by observing prompt 2078500300011 fission neutrons with a proton recoil detector placed 2078500300012 to one side of the sample but outside the neutron 2078500300013 beam. 2078500300014 -Measurements with a gold sample were used to check 2078500300015 the amount of breakthrough. 2078500300016 -The time-of-flight information (minimum channel 2078500300017 width 1/16 microsec.)was collected and stored by an 2078500300018 on-line computer system capable of accepting several 2078500300019 events peR LINAC cycle. 2078500300020 -The time dependent background was determined by the 2078500300021 black resonance filter technique using samples of 2078500300022 manganese,tantalum and titanium. 2078500300023 Background were measured for two thicknesses of each 2078500300024 material to enable extrapolation to zero thickness. 2078500300025 -A permanent cadmium overlap filter was present in all 2078500300026 measurements. 2078500300027 -The time constant background was determined by 2078500300028 recording events at the end of each accelerator 2078500300029 cycle with a background gate. 2078500300030 -The spectrum of incident neutrons was measured 2078500300031 relative to the Li-6(N,ALPHA) cross-section, using a 2078500300032 lithium glass detector. This detector was placed in 2078500300033 the same position as the sample in the fission yield 2078500300034 measurements and background were determined in an 2078500300035 identical manner using the same filters. 2078500300036 -Fission cross-sections were measured in the energy 2078500300037 range 1 eV to 10 keV by observing prompt fission 2078500300038 neutrons. 2078500300039 DETECTOR (GLASD) Lithium glass detector, monitoring the 2078500300040 incident neutron spectrum. 2078500300041 (SCIN) Four NE-213 proton recoil detectors placed 2078500300042 around the sample, out of the incident neutron beam, 2078500300043 with a pulse shape discrimination system. 2078500300044 This system was used to distinguish the neutron and 2078500300045 gamma-ray events which were then stored as separate 2078500300046 time-of-flight spectra. 2078500300047 -A pulse height bias equivalent to 1.5 MeV neutron 2078500300048 energy was applied in all measurements. 2078500300049 ANALYSIS -The observed time-of-flight spectra for both 2078500300050 the Am-241 and the U-235 were converted to fission 2078500300051 cross-section shapes after correction for background 2078500300052 and incident neutron spectrum energy dependence. 2078500300053 -The U-235 cross-section was placed on an absolute 2078500300054 scale by normalizing the average U-235 fission yield 2078500300055 in the 1 keV to 2 keV range of incident neutron 2078500300056 energy to the value of 7.167 barns given by a recent 2078500300057 status report on the U-235 evaluation in MONIT-REF. 2078500300058 -The Am-241 fission c.s. was then normalized in the 2078500300059 same energy range using the calibration obtained 2078500300060 from the U-235 measurement, and the difference in 2078500300061 the value of nu-bar for Am-241 and U-235, was taken 2078500300062 into account,using the values of Manero and Konshin. 2078500300063 MONITOR ((MONIT)92-U-235(N,F),,SIG,,AV) To determine absolute 2078500300064 scale for Am-241 fission cross section. 2078500300065 (3-LI-6(N,T)2-HE-4,,SIG) Li-6(n,a) reaction was used 2078500300066 to measure incident neutron spectrum. 2078500300067 MONIT-REF (,M.R.Bhat,R,ERDA-NDC-5,1975) U-235 evaluated c-s, 2078500300068 used for normalization. ERDA-NDC-5/L. 2078500300069 REL-REF (N,,F.Manero+,J,REA,10,637,1972) Values of prompt 2078500300070 neutrons nu-bar for Am-241 and U-235, used in 2078500300071 normalization procedure. Value of average nu-bar for 2078500300072 Pu-239, used for correction. 2078500300073 (N,,M.G.Sowerby+,J,ANE,1,409,1974) Evaluated Pu-239 2078500300074 fission cross-section, used in correction for Pu-239 2078500300075 contribution (above 100 eV).Between 50 and 100 eV the 2078500300076 data of U.K. Data Library were used. 2078500300077 PART-DET (PN) Prompt neutrons. 2078500300078 STATUS (APRVD) Data taken from 77KIEV and private 2078500300079 communication, 1978-09-23. Presented on Fig.1 of 2078500300080 reference. 2078500300081 HISTORY (19780926C) 2078500300082 (19781213E) 2078500300083 (19801204A) G.C., MONITOR reaction strings corrected, 2078500300084 error analysis changed. 2078500300085 (19801218E) 2078500300086 CORRECTION -For background. 2078500300087 -For energy dependence of the incident neutron 2078500300088 spectrum. 2078500300089 -For the difference in the value of NU-BAR For Am-241 2078500300090 and U-235. 2078500300091 -For contribution from the Pu-239 impurity (typical 2078500300092 contribution was 50% in 100eV region and less 20% at 2078500300093 10keV). 2078500300094 -Finite sample corrections for self-shielding and 2078500300095 multiple scattering made by the Monte Carlo method, 2078500300096 varied from 4.5% in low energy range to maximum 9% in 2078500300097 the few keV region. 2078500300098 -For detector efficiency. 2078500300099 ERR-ANALYS (ERR-S) Statistical error corresponding to one standard2078500300100 deviation ( 25.%). 2078500300101 This error does not include any uncertainty in the 2078500300102 assumed average cross-section in the 1 to 2 keV 2078500300103 energy interval where the data were normalized. 2078500300104 (ERR-1) Uncertainties in measuring the shape of 2078500300105 incident neutron flux, in normalizing the 2078500300106 cross-section, and in making the sample thickness 2078500300107 correction, were all less about 3.% . 2078500300108 ENDBIB 106 0 2078500300109 COMMON 5 3 2078500300110 EN-NRM-MIN EN-NRM-MAX MONIT ERR-1 ERR-T 2078500300111 KEV KEV B PER-CENT PER-CENT 2078500300112 1. 2. 7.167 3. 25. 2078500300113 ENDCOMMON 3 0 2078500300114 DATA 4 23 2078500300115 EN-MIN EN-MAX DATA ERR-S 2078500300116 KEV KEV MB MB 2078500300117 5.0000E-02 6.0000E-02 3.8000E+02 9.5000E+01 2078500300118 6.0000E-02 7.0000E-02 7.2200E+02 1.8100E+02 2078500300119 7.0000E-02 8.0000E-02 4.3000E+02 1.0800E+02 2078500300120 8.0000E-02 9.0000E-02 5.4900E+02 1.3700E+02 2078500300121 9.0000E-02 1.0000E-01 2.3700E+02 5.9000E+01 2078500300122 1.0000E-01 2.0000E-01 3.2000E+02 8.0000E+01 2078500300123 2.0000E-01 3.0000E-01 2.8400E+02 7.1000E+01 2078500300124 3.0000E-01 4.0000E-01 3.0400E+02 7.6000E+01 2078500300125 4.0000E-01 5.0000E-01 2.5800E+02 6.5000E+01 2078500300126 5.0000E-01 6.0000E-01 2.0700E+02 5.2000E+01 2078500300127 6.0000E-01 7.0000E-01 1.8800E+02 4.7000E+01 2078500300128 7.0000E-01 8.0000E-01 2.1400E+02 5.4000E+01 2078500300129 8.0000E-01 9.0000E-01 1.2400E+02 3.1000E+01 2078500300130 9.0000E-01 1.0000E+00 1.7400E+02 4.4000E+01 2078500300131 1.0000E+00 2.0000E+00 1.1200E+02 2.8000E+01 2078500300132 2.0000E+00 3.0000E+00 9.4300E+01 2.4000E+01 2078500300133 3.0000E+00 4.0000E+00 9.2700E+01 2.3000E+01 2078500300134 4.0000E+00 5.0000E+00 7.8400E+01 2.0000E+01 2078500300135 5.0000E+00 6.0000E+00 6.8100E+01 1.7000E+01 2078500300136 6.0000E+00 7.0000E+00 9.3000E+01 2.3000E+01 2078500300137 7.0000E+00 8.0000E+00 8.0100E+01 2.0000E+01 2078500300138 8.0000E+00 9.0000E+00 6.4600E+01 1.6000E+01 2078500300139 9.0000E+00 1.0000E+01 5.9700E+01 1.5000E+01 2078500300140 ENDDATA 25 0 2078500300141 ENDSUBENT 140 0 2078500399999 SUBENT 20785004 20080122 21932078500400001 BIB 8 34 2078500400002 REACTION (95-AM-241(N,F),,WID) 2078500400003 METHOD (TOF) See SUBENTRY 20785002 and 20785003. 2078500400004 ANALYSIS -Based on the assumption that to a first approximation 2078500400005 the ratio,R,of fission neutron to gamma-ray yield for 2078500400006 a particular resonance is given by: 2078500400007 ***************************************************** 2078500400008 * R = E(F,N)*NU-BAR(P)*G(F)/ * 2078500400009 * (G(G)*E(C,G)+G(F)*E(F,G)) * 2078500400010 ***************************************************** 2078500400011 where E(F,N) is the detector efficiency for fis. n., 2078500400012 E(C,G) and E(F,G) the overall efficiencies for 2078500400013 detecting capture and fission gamma-rays, 2078500400014 G(F),G(G) are fission and capture widths. 2078500400015 -Authors took as good approximation the following 2078500400016 value: 2078500400017 G(F) = C*G(G)*(R/NU) 2078500400018 where C is about 2., obtained by calibration from 2078500400019 U-235 data. 2078500400020 ASSUMED (ASSUM1,95-AM-241(N,G),,WID,,G) Total radiation width 2078500400021 assumed to be constant and equal to 40 milli-eV. 2078500400022 (ASSUM2,92-U-235(N,G),,WID,,G)Same assumption as above.2078500400023 REL-REF (N,,F.Manero+,J,REA,10,637,1972) Values of average 2078500400024 NU-BAR, used in analysis . 2078500400025 STATUS (APRVD) Data Taken From 77KIEV and private 2078500400026 communication, 1978-09-23. 2078500400027 (TABLE) Table 1 of 1st reference. 2078500400028 (DEP,20785002) 2078500400029 (DEP,20785003) 2078500400030 HISTORY (19780926C) 2078500400031 (19781213E) 2078500400032 (19801105A) G.C., Error analysis changed. 2078500400033 (19801218E) 2078500400034 ERR-ANALYS (ERR-1) Largest source of error was a systematic one 2078500400035 due to normalization and was thought to be 15 %. 2078500400036 ENDBIB 34 0 2078500400037 COMMON 3 3 2078500400038 ERR-1 ASSUM1 ASSUM2 2078500400039 PER-CENT MILLI-EV MILLI-EV 2078500400040 1.5000E+01 40. 40. 2078500400041 ENDCOMMON 3 0 2078500400042 DATA 2 12 2078500400043 EN-RES DATA 2078500400044 EV MILLI-EV 2078500400045 1.28 4.0000E-01 2078500400046 1.93 6.0000E-02 2078500400047 2.37 1.6000E-01 2078500400048 2.60 1.4000E-01 2078500400049 3.97 1.3000E-01 2078500400050 4.97 3.8000E-01 2078500400051 5.42 5.5000E-01 2078500400052 6.12 3.4000E-01 2078500400053 6.74 8.0000E-02 2078500400054 8.17 1.9000E-01 2078500400055 9.11 1.7000E-01 2078500400056 9.85 8.5000E-01 2078500400057 ENDDATA 14 0 2078500400058 ENDSUBENT 57 0 2078500499999 ENDENTRY 4 0 2078599999999