1. Determination of radiative neutron capture cross sections for unstable nuclei by Coulomb dissociation H. Utsunomiya (Konan University) Outline 1.Methodology of the  SF method 2.Applications with real photons 3. Applications with virtual photons RIKEN Seminar Nov. 1, 2011

2. Collaborators H. Utsunomiya a), H. Akimune a), T. Yamagata a), H. Toyokawa c), H. Harada d), F. Kitatani d), Y. -W. Lui e), S. Goriely b) I. Daoutidis b), D. P. Arteaga f), S. Hilaire g), and A. J. Koning h) a)Department of Physics, Konan University, Japan b)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 sections for unstable nuclei in 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  -stability if samples can be prepared. ---> s-process Indirect experimental method is called in for unstable nuclei along the valley of  -stability ---> s-process neutron-rich region ---> r-process surrogate reaction technique ANY OTHER?

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

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

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

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

8. SnSn GDR PDR, M1 ( ,n) ( ,  ’) Particle -  coin. CD Oslo method R. Schwengner A. Zilges M. Guttormsen (p,p’) A. Tamii P. von Neumann-Cosel A. Tamii P. von Neumann-Cosel A. Tonchev

9. SnSn ( ,n) GDR Methodology of  SF method STEP 1 Measurements of ( ,n) c.s. near Sn A-1 A A ( ,n)  SF STEP 1

10. SnSn Methodology of  SF method STEP 2 Normalization of  SF Extrapolation of  SF by models SnSn ( ,n) GDR A-1 A A ( ,n)  SF STEP 1

11. JUSTIFICATION BY REPRODUCING KNOWN (n,  ) C.S. Methodology of  SF method STEP 2 known (n,  ) SnSn SnSn ( ,n) GDR A-1 A A ( ,n)  SF STEP 1

12. neutron capture by unstable nucleus Methodology of  SF method STEP 3 (n,  ) to be deduced A+1 A+2 ( ,n) STEP 3 A+1 X(n,  ) A+2 X known (n,  ) A-1 A A ( ,n) STEP 1 STEP 2 Extrapolation is made in the same way as for stable isotopes. ( ,n) GDR SnSn STEP 1 STEP 2

13. 6 6 Sn 116 117 118119120 121 27 h 122 123 129 d 124 105 106 107 6.5 10 6 y 108 Pd 909192 93 1.53 10 6 y 94 95 64 d 96 Zr 77 78 79 2.95 10 3 y 80 Se 76 75 120 d 89 3.27 d 104 6 6 115 Applications LLFP (long lived fission products) nuclear waste Astrophysical significance Present ( ,n) measurements Existing (n,  ) data 7 3 5 4 H.U. et al., PRC82 (2010) H. Utsunomiya et al., PRC80 (2009) H.U. et al., PRL100(2008) PRC81 (2010) To be published (n,  ) c.s. to be deduced

14. Inverse Compton Scattering  = E e /mc 2 “photon accelerator” Laser Compton scattering  -ray beam

15. =1064, 532 nm AIST (National Institute of Advanced Industrial Science and Technology)

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

17. 909192 93 1.53 10 6 y 94 95 64 d 96 Zr 89 3.27 d Applications LLFP (long lived fission products) nuclear waste Astrophysical significance Present ( ,n) measurements 5 Measurements of ( ,n) cross sections Justification of  SF with existing (n,  ) data STEP 1 STEP 2 Investigation of  SF that reproduces ( ,n) cross sections Extrapolation of  SF below S n STEP 3 Prediction of (n,  ) cross sections for 93 Zr and 95 Zr

18. STEP 1 – ( ,n) 断面積 の中性子しきい値近傍での高精度測定 91Zr 92Zr 94Zr 96Zr

19. Application STEP 2 – Extrapolation of  SF to the low-energy region HFB+QRPA E1 strength supplemented with a giant M1 resonance in Lorentz shape E o ~ 9 MeV,  ~ 2.5 MeV,  o ~ 7 mb ~ 2% of TRK (Thomas-Reiche-Kuhn) sum rule of GDR HFB+QRPA + Giant M1 92Zr

20. Application STEP 2 – Justification of the adopted  SF TALYS code of the HF model

21. Application STEP 2 – Justification of the adopted  SF

22. 93 Zr[T 1/2 =1.5×10 6 y] Results for Zr isotopes long-lived fission product nuclear waste

23. 95 Zr[T 1/2 =64 d] s-process branching 30-40% uncertainties

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

25. 6 6 Sn 116 117 118119120 121 27 h 122 123 129 d 124 6 6 115 Applications 7

26. STEP 1 Measurement of ( ,n) cross sections Sn isotopes H. Utsunomiya et al., PRC80 (2009)

27. HFB+QRPA E1 strength supplemented with a pygmy E1 resonance in Gaussian shape E o ~ 8.5 MeV,  ~ 2.0 MeV,  o ~ 7 mb ~ 1% of TRK sum rule of GDR STEP 2 – Extrapolation of  SF to the low-energy region HFB+QRPA + PDR

28.  SF for Sn isotopes Toft et al., PRC 81 (2010) PRC 83 (2011) Comparison with the Oslo method

29. STEP 2 – Justification of the extrapolated  SF

30. STEP 3 – Statistical model calculations of (n,  ) cross sections for radioactive nuclei 121 Sn[T 1/2 =27 h] 123 Sn[T 1/2 =129 d] Uncertainties: 30-40% Uncertainties: a factor of 3

31. 105 106 107 6.5 10 6 y 108 Pd 104 Applications LLFP (long lived fission products) nuclear waste Astrophysical significance 3

32. STEP 1 Measurement of ( ,n) cross section Pd isotopes

33.  SF for 108 Pd STEP 2 – Extrapolation of  SF RMF + QRPA D. P. Arteaga and P. Ring, Phys. Rev. C77, 034317 (2008) SnSn

34. STEP 2 – Justification of the extrapolated  SF D. P. Arteaga and P. Ring, Phys. Rev. C77, 034317 (2008). S. Goriely, Phys. Lett. B436, 10 (1998). Hybrid Deformed RRPA

35. 107 Pd[T 1/2 =6.5×10 6 y] long-lived fission product nuclear waste 30-40% uncertainties stem from NLD

36. 79 Se(n,  ) 80 Se 77 78 79 2.95 10 3 y 80 Se 76 75 120 d 4 F. Kitatani (JAEA) a systematic measurement for stable Se isotopes ---> complete application of  SF method To be published A. Makinaga et al, PRC79 (2009) Large uncertainties has remained because of a lack of justification in STEP 2.

37. s-process nucleosynthesis and stellar models Main component Weak component Zr 〜 Bi Fe 〜 Zr Main Weak Zr AGB stars （ 1 ≤ M ≤ 3 ） He-shell burning Massive stars （ 8 ≤ M ） Core He burning Carbon burning 12 C( 12 C,n) 23 Mg kT ≈ 91 keV n n ≈10 11 cm -3 22 Ne( ,n) 25 Mg kT=26 keV, n n ≤10 6 cm -3 13 C( ,n) 16 O kT=8 keV, n n ≈10 7 cm -3 22 Ne( ,n) 25 Mg kT=23 keV, n n ≤10 11 cm -3  (E): E ： 0.3 〜 300 keV MACS

39. s-process branching nuclei F. Käppeler et al., Rev. Mod. Phys. 83, 157 (2011) s-only nuclei The s-process branching is a good measure of the stellar neutron density and temperature. 151 Sm(n,  ) @ n-TOF (CERN) Sm 2 O 3, 89.9% 151 Sm, 206.4 mg

40. Normal applications of the  SF method with real photons requires at least 2 neighboring stable isotopes. s-process branching nuclei F. Käppeler et al., Rev. Mod. Phys. 83, 157 (2011) ９ branching nuclei 63Ni 79Se 81Kr, 85Kr 95Zr 147Nd 151Sm 153Gd 185W (n,  ) to be deduced A+1 A+2 ( ,n) known (n,  ) A-1 A A ( ,n)

41. s-process branching nuclei F. Käppeler et al., Rev. Mod. Phys. 83, 157 (2011) Some s-process branching nuclei have only one stable isotope. stable 133Cs 159Tb 165Ho 169Tm 181Ta 203Tl branching 134,135Cs 160Tb 163Ho 170,171Tm 179Ta 204Tl 8 branching nuclei

42. Some s-process branching nuclei have 2 stable isotopes that are not neighboring to each other. s-process branching nuclei s-only nuclei 3 branching nuclei stable 151,153Eu branching 152,154,155Eu

43. Coulomb dissociation experiments with SAMURAI at RIKEN-RIBF s-process branching nucleihalflife(yr)Coulomb dissociation (n,  ) data 134Cs,135Cs2.0652, 2.3× 10 6 136Cs,135Cs,134Cs133Cs 152Eu*13.537153Eu, 152Eu151Eu 154Eu,155Eu8.593, 4.753156Eu,155Eu,154Eu153Eu 160Tb0.198161Tb,160Tn159Tb 163Ho4570164Ho,166Ho165Ho 170Tm,171Tm0.352, 1.921172Tm,171Tm,170Tm169Tm 179Ta1.82180Ta,182Ta181Ta 204Tl3.78205Tl,204Tl203Tl 11 branching nuclei 18 Coulomb dissociations

44. Ambitious application of the  SF method to the r-process The 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  SF for Sn isotopes 116Sn,…., 124Sn (7 stable) → → → 132Sn 132Sn( ,n) data: GSI Coulomb dissociation data for 132Sn 131 Sn(n,  ) 132 Sn cross sections in the r-process nucleosynthesis

47. New  -ray Beam Line @ NewSUBARU

48. Summary  SF method: (n,  ) c.s. for unstable nuclei 1. Nuclear Experiment: ( ,n) c.s. real photons for stable nuclei virtual photons for unstable nuclei (CD) 2. Nuclear Theory: models of  SF models of NLD primary strength: low-energy E1 of GDR extra strengths: PDR, M1 3. Coulomb dissociation experiments with SAMURAI @ RIKEN- RIBF play a key role in the application of the  SF method.