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H. Utsunomiya (Konan University)

Probing Nuclear Statistical Quantities by Photodisintegration 光核反応による統計的核物理量の研究. H. Utsunomiya (Konan University). RIKEN Workshop, 25-26 September 2008. Outline 1. Japan synchrotron radiation facilities 2. Photodisintegration for nuclear statistical quantities

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H. Utsunomiya (Konan University)

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  1. Probing Nuclear Statistical Quantities by Photodisintegration光核反応による統計的核物理量の研究 H. Utsunomiya (Konan University) RIKEN Workshop, 25-26 September 2008 Outline 1. Japan synchrotron radiation facilities 2. Photodisintegration for nuclear statistical quantities 3. Systematic study of E1 & M1 g strength functions for Zr isotopes 4. Pigmy E1 resonance for Sn isotopes 5. Nuclear level density 6. Summary

  2. Collaborators Konan U.H. Utsunomiya,T. Kaihori, H. Akimune, T. Yamagata AIST K. Yamada, H. Toyokawa, T. Matsumoto, H. Harano JAEA H. Harada, F. Kitatani, S. Goko RCNPT. Shima NewSUBARU S. Miyamoto Texas A&M, USAY.-W. Lui ULB, Brussels, Belgium S. Goriely CEA-Bruyères-le-Châtel, France S. Hilaire ZG Petten, The NetherlandsA.J. Koning この研究発表は、旧電源開発促進対策特別会計法及びに特別会計に関する法律（エネルギー対策特別会計）に基づく文部科学省からの受託事業として、北海道大学が実施した平成18年度、平成19年度および平成20年度「高強度パルス中性子源を用いた革新的原子炉用核データの研究開発」の成果を含みます。

  3. AIST Electron Accelerator Facility Stroge Ring NIJI-IV General-purpose Storage Ring TERAS ・VUV-IR自由電子レーザー ・レーザー逆コンプトン光 ・偏光アンジュレータ光 ・放射光 400MeVElectron Linear Acc. TELL S-band small linear acc. ・レーザーコンプトン散乱 　　　　　　準単色ps-fsⅩ線 ・コヒーレントテラヘルツ波 Small Storage RingNIJI-II ・SRプロセス Pulsed slow positron beam line ・ナノメートル～原子レベル空孔計測

  4. Tsukuba Electron Ring for Acceleration and Storage (TERAS) l=532 nm 2.4 eV

  5. Eg = 1 – 40 MeV Inverse Compton Scattering “photon accelerator” g = Ee/mc2

  6. Neutron Detector System Triple-ring neutron detector 20 3He counters (4 x 8 x 8 ) embedded in polyethylene triple ring detectors Monitor: NaI(Tl)

  7. New SUBARU facility 兵庫県立大 高度研 SPring-8 1 GeV直線加速器 8 GeVシンクロトロン NewSUBARU

  8. Gamma Detector Target Beam Shutter 50 300 300 1650 450 1550 Present: limited space Shima: JPS meeting at Yamagata (2008) 4He(g,p)3H (preliminary)

  9. 実効線量限度 6μSv/h以上の範囲 5000 3000 3000 実験中立ち入り禁止区域 8000 beam輸送管 輸送管内ガス:空気 実験ターゲット （&中性子検出器） NaI(Tl)検出器 Future: Open-space beam line?

  10. Radiative Capture and Photodisintegration Nuclear Statistical Quantities in the Hauser-Feshbach model A(x, g)B (x= n, p, d, t, 3He, a) x= n: s & r processes Optical potential Level density continuum Mass, deformation A + x g-ray strength function Modified from RIPL1 Handbook/IAEA-TECDOC http://www-nds.iaea.org/ripl/ Discrete levels Ex, Jp B

  11. Neutron Capture and Photodisintegration Brink hypothesis: GDR is built on excited states. sn(E) GDR (g,n) (n,g) Gamow peak Sn Ex (Z, A-1) Key issues ng(E,T) (g,g’) ・E1, M1 g SF above and below Sn ・NLD Planck Distr. (Z,A)

  12. Main ingredients in the Talys code Talys code: Koning, Hilaire, Duijvestijn, Proc. Int. Conf. on Nuclear Data for Science and Technology AIP Conf. Proc. 769, 1154 (2005). • E1 g strength function Lorentzian models:Axel, PR126 (1962), Kopecky & Uhl, PRC41 (1990) HFB+QRPA model: Goriely, Khan, Samyn, NPA739 (2006) • Nuclear Level density HFB+ Combinatorial model: Hilaire & Goriely, NPA779 (2006) • Spin-flip giant M1 g strength function by Bohr & Mottelson Global systematics in RIPL Handbook Lorentzian function : Eo=41A-1/3 MeV, Go= 4 MeV, fM1=1.58 10-9 A0.47 MeV-3 at 7 MeV

  13. (g,n) cross sections on Zr isotopes 91Zr(g,n)90Zr Threshold behavior of (g,n) cross sections is given by 92Zr(g,n)91Zr In the E1 photo-excitation, is allowed. However, the experimental cross sections are strongly enhanced from the expected behavior. 94Zr(g,n)93Zr

  14. The Lorentzian parametrization of the E1 g-ray strength function 91Zr(n,g)92Zr 92Zr(g,n)91Zr • 10 12 14 16 • E [MeV] The generalized Lorentzian parametrization of the E1 g-ray strength function significantly underestimates the cross sections . The standard Lorentzian parametrization of the E1 g-ray strength function for 92Zr can fit the (g,n) data, but strongly overestimates (n,g) cross sections.

  15. M1 strength in Zr isotopes in the photoneutron channel H. Utsunomiya et al., PRL100 (2008) 91Zr(g,n)90Zr 91Zr(n,g)92Zr M1 E1 92Zr(g,n)91Zr M1 E1 94Zr(g,n)93Zr The HFB+QRPA E1 gSF Plus M1 resonance Eo= 9 MeV, σ0=7.5mb, G=2.5MeV in Lorentz shape. M1 E1

  16. M1 strength in Zr isotopes M1 (p,p’): giantM1 resonance GDR Sn E1 Crawley et al., PRC26, 87 (1982) Nanda et al., PRL51 (1982) Anantaraman et al., PRL46 (1981) M1 Bertrand et al., PL103B (1981) E1 Sn Other probes M1 E1 (g,g’): giantM1 resonance Sn Laszewski et al., PRL59 (1987) M1 E1 (e,e’) weak & fragmented Meuer et al., NPA 1980 Sn Excitation Energy

  17. 96Zr(g,n)95Zr • g-ray strength functions • E1 : HFB+QRPA, Goriely et al. (2004) • M1 resonance in Lorentz shape • Eo= 8.5 MeV(9.0 MeV for 91,92,94Zr) • s0 =7.5mb • =2.5 MeV Preliminary 96Zr(g,n)95Zr NLD HFB+ Combinatorial Goriley & Hilaire (2008) Optical potential Koning & Delaroche (2003)

  18. 95Zr(n,g)96Zr 95Zr(n,g)96Zr 95Zr[T1/2=64 d](n, g)96Zr s-process branching Uncertainties : 30 – 40% in 0.01 – 1 MeV Preliminary Sources of uncertainties NLD models 1.HFB+Combinatorial 2.BSFG 3.CT (Constant Temp.) 4.GSM (Gen. Superfluid) 5.HFBCS+statisticales Optical potential models 1.KD (Koning & Delaroche 2003) 2.JLM (Bauge et al. 2001)

  19. 93Zr(n,g)94Zr 93Zr(n,g)94Zr 93Zr[T1/2=1.5 ×106 y](n, g)94ZrTransmutation of nuclear waste 93Zr known as LLFP (long-lived fission products) Preliminary Uncertainties : 40 – 50% in 0.01 – 1 MeV Sources of uncertainties NLD & Optical pot. models

  20. Pigmy E1 resonance in 117Sn 117Sn(g,n)116Sn 116Sn(n,g)117Sn Lorentz型のガンマ線強度関数（破線）で 117Sn(g,n)断面積はフィットできるが、 116Sn(n,g)断面積はoverestimateする。 断面積のしきい値振る舞い（1点鎖線、l=1）に 従わない。 Solution：　HFB+QRPAガンマ線強度関数（点線）にPigmy resonance （Eo=8.5 MeV, G=2 MeV, so=7 mbin Gaussian shape）を導入すれば、117Sn(g,n)断面積だけでなく116Sn(n,g)断面積もほぼ再現できる。

  21. Pigmy resonance in 116Sn しきい値が高いeven-A核である116Snの場合は、pigmy resonanceのhigh energy partが(g,n)断面積に寄与していると考えられる。

  22. g-ray SF for 117,116Sn Comparison with Oslo data 117Sn 116Sn

  23. 9/2-, 7/2-, 5/2- 4+, 3+ 5-, 4-, 3-, 2- … … 5- (7/2+) E1 s-process production of 180Tam s wave neutron s wave neutron 179Ta T1/2=1.82y 6+ Nuclear Level Density 7- s(9-) = stotal - sgs 8+ T1/2 > 1.2×1015y 9- 75.3 2+ 42 T1/2=8.152h 1+ 0 180Ta 7/2+ 181Ta

  24. Experimental results, and comparison with theoretical models Goko et al. Phys. Rev. Lett. 96, 192501 (2006) Combinatorial NLD Hilaire & Goriely, NPA779 (2006) HF + BCS NLD High-spin states with are needed in Ex < 5 MeV. Present work (2006) IAEA : Lee et al. (1998)

  25. Summary • The gSF and NLD are key nuclear statistical quantities in the Hauser-Feshbach model calculations of reaction rates of direct relevance to the nucleosynthesis of heavy elements. • Systematic studies of extra g-ray strength arising from M1 and pigmy E1 resonance in the low-energy tail of GDR are important to improve the predictive power of the Hauser-Feshbach model for the nucleosynthesis of heavy elements. • The unique spin and parity of isomeric states can be a good probe of NLD by measuring relevant partial cross sections

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