Gamma-ray strength functions and a new dimension of partial GDR cross section measurements. Hiroaki Utsunomiya

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1 6 th Workshop on Nuclear Level Density and Gamma strength Oslo, May 8-12, 2017 Gamma-ray strength functions and a new dimension of partial GDR cross section measurements Hiroaki Utsunomiya Department of Physics, Konan University Kobe, Japan 1. The gsf Method for a Unified Understanding of (g,n) and (n,g) Reactions 2. New Dimension of Partial GDR Cross Section Measurements

2 International Atomic Energy Agency Coordinated Research Project F41032 IAEA-CRP F year-project ( ) Project Officer: P. Dimitriou H. Utsunomiya (Konan University, Japan) V. Varlamov (Moscow State University, Russian Federation) N. Iwamoto (JAEA, Japan) Y-S. Cho (KAERI, S. Korea) D. Filipescu (IFIN-HH/ELI-NP, Romania) R. Xu (CIAE, China) R. Schwengner (HZDR, Germany) T. Kawano (LANL, USA) R. Firestone (University of California, Berkely, USA) T. Belgya (CER / Hungarian Academy of Sciences, Hungary) S. Goriely (Universite Libre de Bruxelles, Belgium) V. Plujko (Taras Shevchenko National University, Ukraine) M. Wiedeking (ithemba LABS, S. Africa) S. Siem (University of Oslo, Norway) M. Krticka (Charles University in Prague, Czech Rep.) Publication of two compilations in 2020 Updated photonuclear data library Reference database of photon strength functions

3 PHOENIX* Collaboration for the IAEA-CRP F41032 *Photo-excitation and neutron emission cross (x) sections H. Utsunomiya Konan University S. Goriely S. Miyamoto MoU MoU ULB Belgium NewSUBARU Japan MoU MoU U of Oslo Norway ELI-NP Romania S. Siem T. Renström G. Tveten A.-C. Larsen D. Filipescu I. Gheorghe G. Fan H. Wang MoU SINAP China MoU Moscow State U Russia V. Varlamov S. Belyshev K. Stopani

4 LEPS, LEPS2 GeV g SPring8 8 GeV e- storage ring SACLA 8 GeV e- linac 8 GeV e- synchroton 1 GeV e- Linac NewSUBARU MeV g 4

5 Laser Compton scattering 2 Eg 4g L g= E e /mc 2 (Lorentz factor) 2 x 10 3 for E e =1 GeV Energy amplification 2 E g / L 4g ~ 1.6 ε L 1eV E γ 16 MeV 10 7

6 Energy profile of the LCS g-ray beam - high- & meadium-energy g-ray beams 10cm Pb double collimators C1=6mm f, C2=2mm f Beam profile monitor: 3.5 x 4.0 LaBr 3 (Ce) Energy spread % in FWHM GEANT4 simulations

7 The gsf Method for a Unified Understanding of (g,n) and (n,g) Reactions The (g,n) and (n,g) Reactions are interconnected through the g-ray strength function based on the Brink hypothesis of the approximate equality of upward and downward gsfs. Radiative neutron capture A X(n,g) A+1 X n+ A X continuum E, J, p Photoneutron emission A+1 X(g,n) A X f X ( g ) T X ( g ) 2p (2 1) g f X ( g ) 2 1 g (phc) 2 abs X ( g ) 2 1 g S n Brink Hypothesis A+1 X f X ( g ) f X ( g ) g S n

8 (g,n) cross sections for Nd isotopes H.-T. Nyhus et al., PRC 91 (2015) gsf Gogny HFB + QRPA D1M interaction M. Martini et al., Nucl. Data Sheets, 118 (2014) S. Péru and H. Goutte, PRC 77 (2008) S. Péru and M. Martini, EPJA 50 (2014) S. Goriely et al., PRL 102 (2009) Skyrme HFB + QRPA BSk7 interaction S. Goriely, E. Khan and M. Samyn, NPA 739 (2004)

9 (n,g) cross sections for Nd isotopes

10 (g,n) cross sections for Sm isotopes D.M. Filipescu et al., PRC 90 (2014)

11 (n,g) cross sections for Sm isotopes

12 (n,g) cross sections for radioactive nuclei 1.93d 153 Sm 10.98d 147 Nd

13 117 Sn H. Utsunomiya et al., PRC 80 (2009) PRC 84 (2011)

14 Sn isotopes Mo isotopes H. Utsunomiya et al., PRC 84 (2011) H. Utsunomiya et al., PRC 88 (2013)

15 74 Ge T. Renstrøm et al., PRC 93 (2016)

16 New Dimension of Partial GDR Cross Section Measurements The ultimate goal is to resolve the long-standing discrepancy between the Livermore and Saclay data of (g,xn) cross sections. The majority of experimental data for partial photonuclear reaction cross sections were obtained at Livermore (USA) and Saclay (France) Atlas of Photoneutron cross sections obtained with monoenergetic photons (S.S.Dietrich, B.L.Berman. Atom. Data and Nucl. Data Tables, 38 (1988) 199) Berman s library - EXFOR entries L0001 L0059 (~ 174 data sets) Other - 10 Livermore - 83 Both Saclay Many bremsstrahlung data Main problem Courtesy of Varlamov

17 Courtesy of Varlamov IAEA Research Contract N Evaluation of Partial and Total Photoneutron Reactions Cross Sections Using New Objective Physical Data Reliability Criteria Main problem for 19 nuclei investigated in both Labs: (g, 1n) cross sections are larger at Saclay but those for (g, 2n) - at Livermore. MSU SINP CDFE V.V.Varlamov, N.N.Peskov, D.S.Rudenko, M.E.Stepanov. Consistent Evaluation of Photoneutron Reaction Cross Sections Using Data Obtained in Experiments with Quasimonoenergetic Annihilation Photon Beams at Livermore (USA) and Saclay (France). INDC(CCP)-440, IAEA NDS, Vienna, Austria, 2004, p Tb (g,1n) (g,2n) Ratios of integrated cross sections R int = int S / int L very large small Squares - - ratios for (g, 1n) reactions are larger than 1.0: <R> ~ Triangles - - ratios for (g, 2n) reactions are smaller than 1.0: <R> ~ st Research Coordination Meeting, 4 8 April, IAEA CRP (F41032) Updating Photonuclear Data Library and Generating a Reference for Photon Strength Functions 5/11/ Main problem

18 Direct neutron-multiplicity sorting Let us consider (g,xn) reactions with x = 1, 2, and 3.

19 g pulsed beam at 1 khz 1n 2n 3n 1ms 1ms 1ms However, what we can measure is NOT the number of reactions BUT the number of neutrons observed. Here, the detection efficiency is independent of neutron kinetic energies. We can solve a set of equations to obtain N 1, N 2, and N 3.

20

21 N ( E21) (1 ( E22)) N2 ( E22) (1 ( 21)) 2 E

22 Flat-efficiency neutron detector Configurati 3 He Distance on counters [cm] Ring Ring Ring Total 31 Total efficiency = 36.5 ± 1.6% over E n = 10 kev 5.0 MeV

23 Monte Carlo statistical calculations Toshihiko Kawano (LANL) 209Bi(g,xn) reaction 40 MeV (g,2n) (g,3n) (g,4n) (g,5n)

24 Arrival-time distributions

25 Summary Our mission in the IAEA-CRP F41032 is to contribute to constructing two compilations in Updated photonuclear data library (g, xn) cross sections Reference database of photon strength functions (g, n) cross sections Bi, 9Be 203Tl, 205Tl, 89Y Au, 169Tm, 89Y 192Os, 185Re, 138Ba, 137Ba, 64Ni, 61Ni, 60Ni, 58Ni, 13C Ta, 165Ho, 59Co 184W, 183W, 182W, 68Zn, 66Zn, 64Zn Tb, 139La, 103Rh 160Gd, 158Gd, 157Gd, 156Gd Probably we will go beyond the mission at ELI-NP and NewSUBARU. Nuclei underlined Done

26 Problem in neutron-multiplicity sorting at Livermore 48 BF 3 counters embedded in a paraffin-moderator

27 Two possible problems in the past data 1. g-ray beams produced by positron annihilation in flight commonly used at Livermore and Saclay 2. Neutron-multiplicity sorting at Livermore Common, but facility dependent g Livermore They carried out two measurements at one energy, one with a positron (e+) beam and the other with an electron (e-) beam.