Comparison of gamma production from thermal neutron
capture of gadolinium with the Monte Carlo simulation
K.Hagiwara(Okayama Univ.)
P.K.Das, T.Tanaka, I.Ou, Y.Yamada, R.Dhir, T.Mori, T.Kayano, M.Sakuda, Y.Koshio (Okayama Univ.)
T.Yano (Kobe Univ.), A.Kimura, H.Harada, N.Iwamoto, S.Nakamura (Japan Atomic Energy Agency)

1. Introduction
Gadolinium (Gd, Z=64)

3. Analysis method

Cross-section ofthermal neutron
cpature[barn]
n+p→d+γ0.3326n+6Li→α+3He
940
n+10B→α+7Li
3837
n+155Gd→156Gd+γ60900
n+157Gd→158Gd+γ
254000The neutron capture reaction on Gdemits γ-rays with total energy of 8MeV.
Need more precise experimental data!
Measuring γ-rays from thermal
neutron capture on Gd

New method of neutrino measurement using
neutron capture on Gd~20µsec

In order to discriminate electron anti-neutrino
and neutrino, Gd2(SO4)3 will be loaded into
Super-Kamiokande. Event tag by positron anddelayed γ-rays generated by Gd.
However, the uncertainty of simulation forreaction on Gd is large!

~50cm
90% captureon Gd

νepn

Gde+γ

Studying model of reaction for thermal
neutron capture on Gd by experiment.

①Event selection

Reaction

25meV① Thermal neutron energy(4meV~100meV).
② BGO detectors for veto counter.
③ Single γ-ray was required.

4meV

②Ge
BGO

Neutron energy(157Gd)③Ge100meV

upper cluster

BGO
GdGdlower cluster

Bad

Good

γ-Emission model
The probability(P) of transitioning from level Ea to level Eb emitting γ-ray(Eγ)
can be expressed by using “Transmission coefficient T” and “Number oflevels ρ(Eb)ΔEb”.
158Gd excited state2-Present and future neutrino experiments using Gd
Abbreviation

Detector

MeasureEGADS

Water Cherenkov

R&D detector for SK-Gd

Water Cherenkov

SRN, SN ν, Solar ν, atm ν, p+ decay

Eγ=Ea-Eb

ANNRI detector

BGO
GenGe
BGO
Neutron beam(21.5m)

Peak detection efficiency by calibration sources
Energy dependence of peak detection
efficiency in range of 0.1~8MeV wasestimated with uncertainty of ±7%.

0.2
0.18
0.16
0.14
0.12
0.1
0.08
0.06
0.04
0.02
0Good agreement between data andsimulation. Detectors were precisely
calibrated.

138

Unit : mmExperimental Information
PeriodTargetTotal events
Calibration
source2000

4000

2012 B0025
2014 B0124
2013/3/14~3/17
2014/12/11~12/16
・Natural Gd(99.99%)
・Enriched Gd
5mm×5mm×10,20µm A=155(91.65%),157(88.4%)
3×109 events
8×109 events
22Na, 60Co, 137Cs, 152Eu,60Co, 137Cs
NaCl(n,γ)

6000
8000
Energy [keV]

Energy histogram

105

Arbitrary

As shown in right figures,
the new model was agreewith better than GLG4sim.
Difference between data andnew model was estimated tobe about ±30%.
(Improvement by order ofmagnitude)

106

65104

4103
102
10Data / MC78

Ge cluster● : 60Co
ー : Simulation▲ : 152Eu◆ : 35Cl(n,γ)

157Gd(n,γ) data70

Top half detector

Peak detection efficiency

Comparison of experimental data and simulation

184.5

Target0+

158Gd ground state

4. Results

VETO detector

BGO detector

ΔEb

Ref. Kopecky et al. PRC 47.312

Neutron beam

NeutronsourceEb…

2. J-PARC/ MLF/ ANNRI
Pulse type beam(highest intensity)(ΔEn/E n~1%, power : 300kW)
Measurement of γ-rays energy
Ge detector
with high accuracy(14 crystals)(ΔEγ=9keV@1.3MeV)PSF E1 resonance parameters
Energy (Ei) Strength(σi) Width(Γi)
[MeV]
[mb]
[MeV]
11.7
165.0
2.6
158Gd
14.9249.0
3.8

The mixing angle θ13

ANNRI Detector

Ea

Peak Efficiency [%]SK-Gd (2018~)

Daya Bay, RENO,
Liquid scintillator
Double Chooz

T(Ea,Eb) can be expressed by Photon Strength
Function(PSF)

ー : Experimental data
ー : New Modelー : GLG4sim Model based on Geant43250 1000
2000
3000
4000
5000
6000
7000
8000
Data / MC
4 ● : Black/Red3 ▲ : Black/Blue
210012345678Energy [MeV]5. Summary
Ø Gd will be used in Super-Kamiokande.
Ø To understand reaction on Gd, two experiments were carried out.
Ø Detector calibration was well performed within ±7%.
Ø Good agreement between experimental data and new model.

The Kobayashi-Masukawa Institute for the Origin of Particles and the Universe, 5-7 Jan 2017 Nagoya

100