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186,187,188 Os resonance analysis at n_TOF

4 December 2006. 186,187,188 Os resonance analysis at n_TOF. Kaori Fujii, P.M.Milazzo (INFN Trieste, Italy) M.Mosconi, F.K äppeler (FZK, Germany) A.Mengoni (IAEA, CERN). Outline. Os capture measurement at n_TOF resonance analysis

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186,187,188 Os resonance analysis at n_TOF

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  1. 4 December 2006 186,187,188Os resonance analysis at n_TOF Kaori Fujii, P.M.Milazzo (INFN Trieste, Italy) M.Mosconi, F.Käppeler (FZK, Germany) A.Mengoni (IAEA, CERN) K.Fujii n_TOF meeting

  2. Outline • Os capture measurement at n_TOF • resonance analysis “Estima” method (l-wave character analysis) parameters estimation with SAMMY • statistics analysis average level spacing (D) strength function (S) K.Fujii n_TOF meeting

  3. Os capture cross sections experiment → application for Re/Os cosmo-chronometer measurement on August 2003 186Os(2g,79%), 187Os(2g,70%),188Os(2g,95%) (n,γ) detection : 2 × C6D6 scintillators • Major part of the analysis → M.Mosconi • Resonance region analysis → K.Fujii K.Fujii n_TOF meeting

  4. Os yields 187Os 188Os 186Os En(eV) M.Mosconi K.Fujii n_TOF meeting

  5. Os Resonance analysis Reference (resonance parameter) • Neutron Cross Sections Mughabghab 1984 , (2006) • Low energy neutron physics Sukhoruchkin 1998 186Os (I=0) En ~ 3.3keV (~130 resonances) 187Os (I=1/2) En ~ 1.0keV (~180 resonances) 188Os (I=0) En ~ 5.0keV (~110 resonances) K.Fujii n_TOF meeting

  6. Estima method (l-wave character analysis) 186Os 187Os 188Os gΓn/(En)1/2 > 10 V1 <gΓn1> confident s-wave gΓn/(En)1/2 > V1 <gΓn1> likely s-wave V1=(kR)2/(1+(kR)2) All resonances are evaluated “s-wave” K.Fujii n_TOF meeting

  7. Resonance analysis with SAMMY 186Os 187Os 188Os 189Os En(eV) + n_TOF data -- SAMMY fit Reference to the transmission experimental data (En,Γn) K.Fujii n_TOF meeting

  8. Distribution of Γγ(s-wave) 186Os 187Os 188Os Γγ (meV) <Γγ0> = 45.09 meV <Γγ0> = 65.54 meV <Γγ0> = 49.51 meV 60±4 meV (Mughabghab) 76±4 meV (Mughabghab) 82±4 meV (Mughabghab) K.Fujii n_TOF meeting

  9. Cumulative sum of the number of resonances (staircase) D0 : s-wave average level spacing ΔE / N-1 (N: resonance numbers) D0= 24.9±0.4 eV (Mughabghab) D0 = 25.55 eV D0= 4.56±0.2 eV (Mughabghab) D0 = 5.89 eV D0= 40±2 eV (Mughabghab) D0 = 47.45 eV K.Fujii n_TOF meeting

  10. s-wave strength function - 1(staircase plot of gΓ0n summation) 186Os 187Os En (eV) En (eV) 188Os S0=<gΓ0n>/<D0> Γ0n = Γn(1/E0)1/2 En (eV) K.Fujii n_TOF meeting

  11. s-wave strength function -2 • S0 : s-wave strength function : <gΓ0n>/<D0> (Γ0n = Γn(1/E0)1/2 : reduced neutron width) n_TOF data Preliminary! K.Fujii n_TOF meeting

  12. Summary • Os resonance parameters estimated <Γγ>: ~20% less than previous data • Statistics analysis going on (average level spacing, strength function…) • astrophysics application : → MACS → the age of the universe K.Fujii n_TOF meeting

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