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ガンマ線強度関数法によるアプローチ

ガンマ線強度関数法によるアプローチ. Approach by the g -ray strength function method. H. Utsunomiya (Konan University) Outline Methodology of the g SF method Applications to unstable nuclei along the valley of b -stability comments on a versatile application based on Coulomb dissociation experiments.

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ガンマ線強度関数法によるアプローチ

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  1. ガンマ線強度関数法によるアプローチ Approach by the g-ray strength function method H. Utsunomiya (Konan University) Outline • Methodology of the gSF method • Applications to unstable nuclei along the valley of b-stability • comments on a versatile application based on Coulomb dissociation experiments 2011年度核データ研究会プログラム 2011年11月16日(水) – 17日(木) 日本原子力研究開発機構テクノ交流館リコッティ

  2. Collaborators H. Utsunomiyaa) , H. Akimunea) , T. Yamagataa) , H. Toyokawac) , H. Haradad), F. Kitatanid) , Y. -W. Luie) , S. Gorielyb) I. Daoutidisb) , D. P. Arteagaf) , S. Hilaireg) , and A. J. Koningh) • Department of Physics, Konan University, Japan • Institut d’Astronomie et d’Astrophysique, ULB, Belgium • c) National Institute of Advanced Industrial Science and Technology, Japan • d) Japan Atomic Energy Agency, Tokai, Naka-gun, Ibaraki 319-1195, Japan • e) Cyclotron Institute, Texas A&M University, USA • f) Institut de Physique Nucléaire, Université Paris-Sud, France • g) CEA,DAM, DIF, Arpajon, France • h) Nuclear Research and Consultancy Group, The Netherlands

  3. Radiative neutron capture cross sectionsfor unstable nuclei in nuclear engineering and nuclear astrophysics Direct measurements at CERN n-TOF, LANSCE-DANCE, Frankfurt-FRANZ and J-Parc ANNRI facilities can target some of unstable nuclei along the valley of b-stability if samples can be prepared. ---> s-process Indirect experimental method is called in for unstable nuclei along the valley of b-stability ---> s-process, neutron-rich region ---> r-process surrogate reaction technique ANY OTHER?

  4. g-ray strength function method H. Utsunomiya et al., PRC80 (2009) follows the statistical model of the radiative neuron capture in the formation of a compound nucleus and its decay by using experimentally-constrained gSF. Radiative neutron capture AX(n,g)A+1X continuum E, J, p decay process gSF NLD n + AX A+1X

  5. Hauser-Feshbach model cross section for AX(n,g)A+1X Total gtransmission coefficient After integrating over J and π nuclear level density g-ray strength function X=E, M l=1, 2, … neutron resonance spacing low-lying levels source of uncertainty gSF method

  6. g-ray strength function: nuclear statistical quantity interconnecting (n,g) and (g,n) cross sectionsin the HF model calculation Radiative neutron capture Photoneutron emission continuum AX(n,g)A+1X A+1X(g,n)AX E, J, p n+AX A+1X Brink Hypothesis

  7. Structure of g-ray strength function Extra strengths Sn GDR 6 – 10 MeV PDR, M1 Primary strength E1 strength in the low- energy tail of GDR

  8. Methodology of gSF method STEP 1 GDR (g,n) Measurements of (g,n) c.s. near Sn STEP 1 gSF (g,n) A-1 A Sn

  9. Methodology of gSF method STEP 2 GDR (g,n) Normalization of gSF Extrapolation of gSF by models STEP 1 gSF (g,n) A-1 A Sn Sn

  10. Methodology of gSF method STEP 2 GDR (g,n) JUSTIFICATION BY REPRODUCING KNOWN (n,g) C.S. STEP 1 gSF (g,n) A-1 A Sn Sn known (n,g)

  11. Methodology of gSF method STEP 3 GDR (g,n) neutron capture by unstable nucleus A+1X(n,g)A+2X STEP 1 STEP 2 STEP 1 STEP 2 gSF (g,n) (g,n) A-1 A A+1 A+2 Extrapolation is made in the same way as for stable isotopes. Sn STEP 3 known (n,g) (n,g) to be determined

  12. Applications LLFP (long lived fission products) nuclear waste Astrophysical significance Present (g,n) measurements Existing (n,g) data H. Utsunomiya et al., PRC80 (2009) (n,g) c.s. to be deduced 121 27 h 123 129 d 6 6 Sn 117 116 118 119 120 122 124 115 7 H.U. et al., PRC82 (2010) 107 6.5 106 y 3 106 108 Pd 105 104 H.U. et al., PRL100(2008) PRC81 (2010) 93 1.53 106 y 95 64 d 5 89 3.27 d Zr 94 90 91 92 96 79 2.95 103 y To be published F. Kitatani et al. 75 120 d Se 78 80 76 77 4

  13. Laser Compton scattering g-ray beam Inverse Compton Scattering “photon accelerator” g = Ee/mc2

  14. AIST (National Institute of Advanced Industrial Science and Technology) l=1064, 532 nm

  15. Detector System Triple-ring neutron detector 20 3He counters (4 x 8 x 8 ) embedded in polyethylene

  16. Applications H. Utsunomiya et al., PRC, in press (2011) H. Utsunomiya et al., PRC80 (2009) 121 27 h 123 129 d 6 6 Sn 117 116 118 119 120 122 124 115 7

  17. Sn isotopes STEP 1 Measurement of (g,n) cross sections

  18. STEP 2 – Extrapolation of gSF to the low-energy region HFB+QRPA + PDR HFB+QRPA E1 strength supplemented with a pygmy E1 resonance in Gaussian shape Eo ~ 8.5 MeV, G ~ 2.0 MeV, so ~ 7 mb ~ 1% of TRK sum rule of GDR

  19. STEP 2– Justification of the extrapolated gSF

  20. STEP 3 – Statistical model calculations of (n,g) cross sections for radioactive nuclei Uncertainties: 30-40% 121Sn[T1/2=27 h] 123Sn[T1/2=129 d] Uncertainties: a factor of 3

  21. Results for Zr isotopes long-lived fission product nuclear waste 93Zr[T1/2=1.5×106 y]

  22. 95Zr[T1/2=64 d] s-process branching 30-40% uncertainties

  23. long-lived fission product nuclear waste 107Pd[T1/2=6.5×106 y] 30-40% uncertainties stem from NLD

  24. Coulomb dissociation in the gSF method s-process branching nucleus (g,n) by Coulomb dissociation A A+1 (n,g) to be determined by gSF method

  25. s-process branching nuclei F. Käppeler et al., Rev. Mod. Phys. 83, 157 (2011)

  26. Coulomb dissociation experiments F. Käppeler et al., Rev. Mod. Phys. 83, 157 (2011) 18 Coulomb dissociations 11 branching nuclei

  27. Ambitious application of the gSF method to the r-process 131Sn(n,g)132Sn cross sections in the r-process nucleosynthesis The astrophysical significance is controversial！ BUT this would be the first application to a very neutron-rich nucleus. A pioneering work is in progress. 1) A systematic study of the gSF for Sn isotopes 116Sn ,…., 124Sn (7 stable) →→→ 132Sn 132Sn(g,n) data: GSI Coulomb dissociation data for 132Sn

  28. Summary gSF method: (n,g) c.s. for unstable nuclei 1. Nuclear Physics Experiment: (g,n) c.s. measurements real photons for stable nuclei virtual photons for unstable nuclei (CD) 2. Nuclear Theory: models of gSF models of NLD primary strength: low-energy E1 of GDR extra strengths: PDR, M1 3. Coulomb dissociation experiments play a key role in a versatile application of the gSF method. SAMURAI + NEBURA @ RIKEN-RIBF ALADIN + LAND @GSI

  29. Determination of (n,g) CS for unstable nuclei 原子力核データ、宇宙核物理（s-process） along the valley of b-stability 宇宙核物理 r-process p-process far from stability 直接測定 Neutron beam (n,g) (g,n) (g,n) Photon beam RI beam ガンマ線強度関数法

  30. Comparison with the surrogate reaction technique Forssèn et al., PRC75, 055807 (2007) Zr isotopes 93Zr(n,g)94Zr 95Zr(n,g)96Zr 1. The surrogate reaction technique gives larger cross sections by a factor of ~ 3 than the gSF method. The surrogate reaction technique gives similar cross sections to those given by the gSF method provided that a choice is made of the Lorentian type of gSF.

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