ENTRY 20588 19840126 00002058800000001 SUBENT 20588001 19840126 00002058800100001 BIB 17 54 2058800100002 INSTITUTE (2FR ILL) M.ASGHAR, EXPERIENCE SITE. 2058800100003 (2FR LYO) A.EMSALLEM,R.CHERY. 2058800100004 (2BLGMOL) C.WAGEMANS 2058800100005 (2BLGBLG) NUCLEAR PHYSICS LABORATORY, GENT. 2058800100006 P.DHONT,J.DERUYTTER. 2058800100007 REFERENCE (J,NP/A,259,(3),429,7603) 2058800100008 AUTHOR (M.ASGHAR,A.EMSALLEM,R.CHERY,C.WAGEMANS,P.DHONDT, 2058800100009 J.DERUYTTER) 2058800100010 TITLE -THE U238(N,ALPHA)TH235 REACTION WITH THERMAL 2058800100011 NEUTRONS- 2058800100012 FACILITY .HIGH FLUX REACTOR OF THE LAUE-LANGEVIN INSTITUTE, 2058800100013 GRENOBLE. 2058800100014 INC-SOURCE (THCOL) 87 M CURVED NEUTRON GUIDE TUBE. 2058800100015 INC-SPECT .VERY PURE THERMAL SPECTRUM. RATIO OF THE NUMBER 2058800100016 OF SLOW NEUTRONS TO THAT OF EPITHERMAL AND FAST 2058800100017 NEUTRONS ABOUT 10E+6. DIRECT GAMMA-RAY FLUX FROM 2058800100018 REACTOR REDUCED BY A FACTOR 1.E+6. 2058800100019 .VERY INTENSE NEUTRON FLUX = 1.E+9 CM-2.SEC-1. 2058800100020 SAMPLE .U238 LAYER PREPARED BY EVAPORATION OF UF4 ON A THIN 2058800100021 VYNS FOIL COVERED WITH GOLD. THICKNESS OF UF4 = 200 2058800100022 +-10 MICRO-G/CM**2. 2058800100023 .ISOTOPIC COMPOSITION IN ATOMS PERCENT = 2058800100024 0.00016+-0.00001 OF U234, 0.01755+-0.00005 OF U235, 2058800100025 LESS THAN 0.00001 OF U236, 2058800100026 99.9823+-0.0001 OF U238. 2058800100027 METHOD (PHD ) PULSE-HEIGHT ANALYSIS. 2058800100028 DETECTOR (SOLST) GOLD-SILICON SURFACE BARRIER DETECTOR, 2058800100029 RESOLUTION = 30 KEV FOR 5 MEV ALPHA PARTICLES. 2058800100030 ANALYSIS .U238(N,ALPHA) CROSS SECTION OBTAINED BY NORMALIZING 2058800100031 THE ALPHA PARTICLE SPECTRUM TO THE KNOWN THERMAL 2058800100032 NEUTRON INDUCED FISSION CROSS SECTION OF U235. 2058800100033 MONITOR (92-U-235(N,F),,SIG,,MXW) 2058800100034 .ENERGY CALIBRATION WAS BASED ON THE KNOWN ENERGY OF 2058800100035 THE NATURAL ALPHA PARTICLES EMITTED BY U238 AND 2058800100036 RN220 AND ITS DAUGHTER PRODUCTS PRODUCED FROM 2058800100037 CONTROLED TH232 IMPURITY PRESENT IN THE VACUUM 2058800100038 CHAMBER. 2058800100039 COMMENT .PRESENT VALUE IS TWO ORDERS OF MAGNITUDE LOWER 2058800100040 THAN PREVIOUS UPPER LIMIT. 2058800100041 .WITH OBTAINED VALUE OF ALPHA ENERGY THE Q-ALPH VALUE 2058800100042 OF THE REACTION AND THE MASS AND Q-BETA VALUES OF 2058800100043 TH225 ARE DEDUCED 2058800100044 .LARGE ALPHA PARTICLE CLUSTERING PROBABILITY FOR 2058800100045 THE U239 COMPOUND SYSTEM IS A POSSIBLE EXPLANATION 2058800100046 FOR THE DISCREPANCIES BETWEEN EXPERIMENTAL VALUE 2058800100047 AND STATISTICAL MODEL CALCULATIONS. 2058800100048 STATUS .DATA TAKEN FROM REFERENCE NUCL.PHYS.A259(1976)429. 2058800100049 HISTORY (760812C) 2058800100050 (761217E) 2058800100051 CORRECTION .BACKGROUND. NO DETAILS GIVEN. 2058800100052 ERR-ANALYS .QUOTED ERROR INCLUDES STATISTICAL ERROR,UNCERTAINTY 2058800100053 IN THE BACKGROUND CORRECTION AND IN THE TARGET 2058800100054 SPECIFICATIONS AND THE INSTABILITY OF THE NEUTRON 2058800100055 BEAM. 2058800100056 ENDBIB 54 0 2058800100057 COMMON 2 3 2058800100058 EN-DUMMY MONIT 2058800100059 EV B 2058800100060 2.5300E-02 5.8760E+02 2058800100061 ENDCOMMON 3 0 2058800100062 ENDSUBENT 61 0 2058800199999 SUBENT 20588002 19840126 00002058800200001 BIB 2 4 2058800200002 REACTION (92-U-238(N,A)90-TH-235,,SIG,,MXW) 2058800200003 THERMAL (N,ALPHA) CROSS SECTION 2058800200004 HISTORY (760812C) 2058800200005 (761217E) 2058800200006 ENDBIB 4 0 2058800200007 NOCOMMON 0 0 2058800200008 DATA 2 1 2058800200009 DATA DATA-ERR 2058800200010 MICRO-B MICRO-B 2058800200011 9.2000E+00 6.0000E-02 2058800200012 ENDDATA 3 0 2058800200013 ENDSUBENT 12 0 2058800299999 ENDENTRY 2 0 2058899999999