ENTRY 22867 20050221 21722286700000001 SUBENT 22867001 20050221 21722286700100001 BIB 13 46 2286700100002 TITLE .s-process branching at 185W revised. 2286700100003 AUTHOR (P.MOHR,T.SHIZUMA,H.UEDA,S.GOKO,A.MAKINAGA,K.Y.HARA, 2286700100004 T.HAYAKAWA,Y.-W.LUI,H.OHGAKI,H.UTSUNOMIYA) 2286700100005 INSTITUTE (2GERTHD,2JPNJAE,2JPNKON,1USATAM,2JPNKTO,2JPNJPN) 2286700100006 REFERENCE (J,PR/C,69,032801,2004) 2286700100007 FACILITY (ESTRG,2JPNAIS) Electron storage ring TERAS at AIST 2286700100008 (Tsukuba, Japan). 2286700100009 INC-SOURCE (MPH,LASER) Tunable monochromatic photon source from 2286700100010 laser Compton scattering - Laser Compton Scattering 2286700100011 photons, LCS. 2286700100012 DETECTOR (HE3SP) Improved neutron detector consisted of 16 2286700100013 individual 3He counters embedded in two rings in a 2286700100014 poliethilene moderator. 2286700100015 METHOD (RINGR) Direct measurement of photoneutrons using the 2286700100016 ring-ratio method: ring-ratio between the count 2286700100017 rates of the inner and outer detector rings depends 2286700100018 on the neutron energy, and hence cfn be used to 2286700100019 estimate the neutron energy. That varied between 2.5 2286700100020 and 4.4 leading to average neutron energies of about 2286700100021 1.2 MeV at highest photon energies and of about 0.3 2286700100022 MeV at lower photon energies. 2286700100023 SAMPLE The target consisted of 1246 mg metallic tungsten 2286700100024 powder highly enriched in 186W to 99.79 % The powder 2286700100025 was pressed to a small self-supporting tablet with a 2286700100026 diameter of 8 mm. 2286700100027 ANALYSIS (UNFLD) For estimation of the reaction cross section 2286700100028 from the experimental reaction yield the unfolding 2286700100029 procedure using the replacement of integral eguation 2286700100030 by Taylor series (because the difference (low-energy 2286700100031 tail) of realistic photon spectrum from ideal is 2286700100032 relatively small) was used. 2286700100033 ERR-ANALYS Statistical errors. 2286700100034 COMMENT The neutron capture cross section of the unstable 2286700100035 s-process branching nucleus 185W has been derived 2286700100036 from experimental data of inverse 186W(g,n)185W 2286700100037 photodisintegration taken with monochromatic photon 2286700100038 beams from laser Compton scattering. The result of 2286700100039 SIG = 553 (60) mb at kT = 30 keV leads to a 2286700100040 relatively high effective neutron density in the 2286700100041 classical s-process of Nn = 4.7 x 10**8 sm**-3. A 2286700100042 realistic model for the s-process in thermally 2286700100043 pulsing asymptotic giant branch stars overestimates 2286700100044 the abundance of 186Os significantly because of the 2286700100045 relatively small neutron capture cross section of 2286700100046 185W. 2286700100047 HISTORY (20050118C) V.V./S.M. 2286700100048 ENDBIB 46 0 2286700100049 NOCOMMON 0 0 2286700100050 ENDSUBENT 49 0 2286700199999 SUBENT 22867002 20050221 21722286700200001 BIB 3 4 2286700200002 REACTION (74-W-185(N,G)74-W-186,,SIG,,MXW) 2286700200003 INC-SPECT .Quasi-maxwellian energy spectrum 2286700200004 STATUS (CURVE) The data from Fig. 3 have been digitized at 2286700200005 the Russia MSU SINP CDFE by V.V.Varlamov. 2286700200006 ENDBIB 4 0 2286700200007 NOCOMMON 0 0 2286700200008 DATA 3 1 2286700200009 KT DATA ERR-S 2286700200010 KEV MB MB 2286700200011 30. 553. 60. 2286700200012 ENDDATA 3 0 2286700200013 ENDSUBENT 12 0 2286700299999 ENDENTRY 2 0 2286799999999