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

6th Workshop on Nuclear Level Density and Gamma strength Oslo, May 8 -12, 2017

IAEA-CRP F41032 5 year-project (2016-2020)

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.)

International Atomic Energy Agency Coordinated Research Project F41032

Reference database of photon

strength functions

Publication of two compilations in 2020

Updated photonuclear data library

Project Officer: P. Dimitriou

PHOENIX* Collaboration for the IAEA-CRP F41032

*Photo-excitation and neutron emission cross (x) sections

Konan University

H. Utsunomiya

ELI-NP Romania

Moscow State U Russia

U of Oslo Norway

SINAP China

ULB Belgium

NewSUBARU Japan

D. Filipescu I. Gheorghe

V. Varlamov S. Belyshev K. Stopani

S. Siem T. Renström G. Tveten A.-C. Larsen

S. Goriely

S. Miyamoto

G. Fan H. Wang

MoU

MoU MoU

MoU

MoU

MoU

4

SPring8

SACLA

NewSUBARU MeV g

1 GeV e- Linac

8 GeV e- synchroton 8 GeV e- linac

8 GeV e- storage ring LEPS, LEPS2 GeV g

Laser Compton scattering

εL〜 1eV Eγ 〜 16 MeV

LE gg

2472 106.1~4/ gg LE

Energy amplification

g= Ee/mc2 (Lorentz factor) 〜 2 x 103 for Ee=1 GeV

Energy profile of the LCS g-ray beam - high- & meadium-energy g-ray beams

Beam profile monitor: 3.5” x 4.0” LaBr3(Ce)

GEANT4 simulations

Energy spread 1.2 – 1.6% in FWHM

10cm Pb double collimators C1=6mmf, C2=2mmf

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.

n+AX

A+1X

E, J, p AX(n,g)A+1X A+1X(g,n)AX

fX (g ) g

2 1

(phc)2X

abs(g )

2 1

g Sn

g Sn

Photoneutron emission Radiative neutron capture

continuum

fX (g ) TX (g )

2pg

(2 1)

fX (g ) fX (g ) Brink Hypothesis

(g,n) cross sections

for Nd isotopes

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)

H.-T. Nyhus et al., PRC 91 (2015)

gSF

(n,g) cross sections for Nd isotopes

(g,n) cross sections for Sm isotopes

D.M. Filipescu et al., PRC 90 (2014)

(n,g) cross sections for Sm isotopes

(n,g) cross sections for radioactive nuclei

10.98d 1.93d 153Sm 147Nd

117Sn

H. Utsunomiya et al., PRC 80 (2009)

PRC 84 (2011)

Mo isotopes Sn isotopes

H. Utsunomiya et al., PRC 84 (2011) H. Utsunomiya et al., PRC 88 (2013)

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

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)

Livermore - 83 Saclay - 81

Other - 10

Both – 42

Main problem

Many bremsstrahlung data

Courtesy of Varlamov

IAEA Research Contract N 20501 “Evaluation of Partial and Total Photoneutron Reactions Cross Sections Using

New Objective Physical Data Reliability Criteria”

MSU SINP CDFE

1st Research Coordination Meeting, 4 – 8 April, IAEA CRP (F41032)

“Updating Photonuclear Data Library

and Generating a Reference for Photon Strength Functions”

5/11/2017 17 Main problem

Main problem for 19 nuclei investigated in both Labs:

(g, 1n) cross sections are larger at Saclay but those for (g, 2n) - at Livermore.

Squares - -

ratios for (g, 1n)

reactions – are

larger than 1.0:

<R> ~ 1.07.

Triangles - -

ratios for (g, 2n)

reactions – are

smaller than 1.0:

<R> ~ 0.84.

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. 37.

small very large

Ratios of integrated cross sections Rint = intS / int

L

159Tb

Courtesy of Varlamov

(g,1n)

(g,2n)

Direct neutron-multiplicity sorting

Let us consider (g,xn) reactions with x = 1, 2, and 3.

g pulsed beam at 1 kHz

1ms 1ms 1ms

1n 2n 3n

Here, the detection efficiency is independent of neutron kinetic energies.

We can solve a set of equations to obtain N1, N2, and N3.

However, what we can measure is NOT the number of reactions

BUT the number of neutrons observed.

))(1()())(1()( 2122222212 EENEEN

Flat-efficiency neutron detector

Total efficiency

= 36.5 ± 1.6% over En = 10 keV – 5.0 MeV

Configurati

on

3He counters

Distance

[cm] Ring 1 4 5.5 Ring 2 9 13.0 Ring 3 18 16.0 Total 31

Monte Carlo statistical calculations

Toshihiko Kawano (LANL)

209Bi(g,xn) reaction 40 MeV (g,2n)

(g,3n)

(g,4n)

(g,5n)

Arrival-time distributions

Summary

Our mission in the IAEA-CRP F41032 is to contribute to constructing two

compilations in 2020.

.

2015 209Bi, 9Be 203Tl, 205Tl, 89Y

2016 197Au, 169Tm, 89Y 192Os, 185Re, 138Ba, 137Ba,

64Ni, 61Ni, 60Ni, 58Ni, 13C

2017 181Ta, 165Ho, 59Co 184W, 183W, 182W,

68Zn, 66Zn, 64Zn

2018 159Tb, 139La, 103Rh 160Gd, 158Gd, 157Gd, 156Gd

Done

Nuclei underlined

Updated photonuclear data

library – (g, xn) cross sections

Reference database of photon strength

functions– (g, n) cross sections

Probably we will go beyond the mission at ELI-NP

and NewSUBARU.

Problem in neutron-multiplicity sorting at Livermore

48 BF3 counters embedded in a paraffin-moderator

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.