Measurement of Relative Intensities of the discrete γ-rays from the thermal
155,157
neutron capture reaction
Gd(n,γ) using ANNRI detector ( J-PARC).
PRETAM KUMAR DAS (Okayama University)
Collaborators : K.Hagiwara, Y.Yamada, I.Ou, T.Yano, R. Dhir, T.Mori, Y.Koshio, M.Sakuda (Okayama Univ.)
A. Kimura, H.Harada, N.Iwamoto, S.Nakamura (JAEA)

1. Introduction, Gd(n,γ) reaction

Relative intensities of γ-rays from the 35Cl(n ,γ)36Cl reaction

γ-ray spectrum of 35Cl(n,γ)36Cl

Peak Energyin [keV]• Among all stable nuclei, Gd has the largest thermal neutron
capture cross-section. Gd(n, γ) reaction emits total ~8MeV γ-rays.

• Application of Gd(n,γ) reaction
Ø Gd(n,γ) reaction is used for neutron tagging toidentify anti-neutrino interactions from other reactions.

n Delayedsignalνep

Gde+γnØ Two clusters of Ge detector + BGO (Bismuth Germanium oxide) anti-Compton
veto detector.
Ø Solid angle : Ge 22％, BGO VETO 55％•Ge

Experimental data are taken for enriched Gd.

Experimental period : 2014.12.11-16 (2014B0126)
Target: Enriched Gd(A=155(91.65%), 157(88.4%) Gd2O3 powder)
Total event: 8×109events
Calibration source : 22Na, 60Co,137Cs, 152Eu, NaCl(CapGam).

2.2. Measurement of Photo-Peak Efficiency :ØAbsolute Efficiency : 60Co .22Na
ØRelative Efficiency : 35Cl(n,γ)36Cl, 152Eu
2.2.1. Measurement of Photo-Peak Efficiency Using Coincidence Method: 60Co source

6977

22.29±0.82

7414
7790
8578

100.00±1.18 100±0.58
82.72±1.01 80.93±0.36
27.54±0.60 26.88±0.16

Live time correction,

γ-ray spectrum of 157Gd (n,γ)158GdN 2( A ) = β T η ( A )ε 2(A ) (1− CγA1η Aε1A )N1( B ) = β T η ( B )ε1( B ) (1− CγB2 η Bε 2B )N 2(B ) = β T η ( B )ε 2(B ) (1− CγB1η Bε1B )N 3 = β T η Aε1( A )η ( B )ε 2(B )W (z)N 4 = β T η ( A )ε 2(A )η ( B )ε1( B )W (z)Let(A) (A)
1(A) (A)2

Where,
β= activity of the radioactive
source (in Bq)
Τ= Measurement time (in sec)
η= Geometrical acceptance
ε= Photo-peak efficiency
εabs=ηε=Absolute photo-peakefficiency.
(B) (B)
1(B) (B)
2a=
βT,b=
ηε,c=
ηε,d=
ηε,e=
ηε,
f=W(z)
2Nd
Nt
4-5MeVNt = number of random timing pulser events.
Nd= number of pulser events detectedLet,h = rL( A), i = rL(B), j = rL( AB)
Where , h= live time correction of detector A,
i= live time correction of detector B.
j=live time correction of AB together.
and ,f=W(z) , W(z) =1+ 0.1020P (z)+ 0.0091P (z)2z = cosθ

σ1⎝⎠ ⎝σ2⎠ ⎝Where ,Cγ2A =is the coincidence summing factor of A due to γ2 .
Cγ1 A =is the coincidence summing factor of A due to γ1.
Cγ2B =is the coincidence summing factor of B due to γ2 .
Cγ1 B =is the coincidence summing factor of B due to γ1 .

NC =NA
γ2At
B
γ1

At
B
γ2

NC =NA
γ1NC =NB
γ2Bt
A
γ1

σ3181
780
897.51+897.62
944962
978998.41+1000.82+1004.04
1107
1119
1184.01+1186
1259.86+1263.51
1324
1437
4925
5436
5542
5582
5783
5903
6420
6750

Relative Intensity for C74Expt. data

10 2NNDC(Cap Gam)

Where θ be the angle between the two detectors.
χ method
22222
2
2(A)
A(A)
A(B)
B(B)
B
⎛
⎞
⎛
⎞
⎛
⎞
⎛
⎞
⎛
⎞
observe−expected⎛ N3 − abefj ⎞ ⎛ N 4 − acdfj ⎞N−hab(1−Cc)
N−hac(1−Cb)
N−iad(1−Ce)
N−iae(1−Cd)
1γ
2γ
1γ
2γ
2χ2 =⎜2121⎟ χ =⎜⎟⎟ + ⎜⎜⎟⎟ + ⎜⎜⎟⎟ + ⎜⎜⎟⎟ + ⎜⎟ +⎜⎟⎝⎠
σ⎜σ4⎠ ⎝⎠ ⎝σ5⎠ ⎝σ6⎠101

10 <101000

2000

3000
4000
5000
Gamma Energy in [keV]

6000

7000

Ø Fair agreement between our data and
NNDC (CapGam) in discrete peaks of
158Gd .

B
N
CγB1 = tANγ 222.3(2)100.0(80)86.1(69)
29.4(24)

245.9
17.5
278.9
11.3
32.4
302.5

32.6

15.6
51.4
11.5
190.1
128.4
21.5
100
86.3
28.5

Relative Intensity, IR[%]
MLF(our data)
100.0±0.24
13.69±0.1331.99±0.14
38.32±0.15
24.99±0.1417.74±0.1214.82±0.1525.26±0.11
19.61±0.11
48.02±0.1512.81±0.13
10.95±133.98±113.22±0.09
0.87±0.06
1.57±0.06
2.40±0.07
2.88±0.08
1.16±0.05
6.65±0.08
1.80±0.06

NNDC(CapGam)100±13.04
13.64±1.533.82±5.05
46.64±5.1529.73±3.28
21.06±1.97
15.5±1.74
24.6±2.86
17.02±1.8843.92±4.82
14.79±1.65
9.27±1.01
4.42±0.49
3.71±0.51
1.09±0.15
1.75±0.23
2.56±0.36
2.02±0.29
1.58±0.22
7.69±0.89
1.96±0.28

Relative intensities of γ-rays from the 155Gd(n ,γ)156Gd reaction

Using MINUT program, we calculated the absolute
photo-peak of detector A and B.

γ-ray spectrum of 155Gd (n,γ)156Gd
Good agreement between data and MC(Geant4) efficiency.

2.2.2 Measurement of Relative Efficiency: 35Cl(n,γ)36Cl
Number of events of any photo peaks
N=βΤηε = Intensity. Efficiency
N
ε=Then efficiency can be written asI
Where I is the intensity of any photo peaks (from tablevalue).

Relative efficiency,

εR =εε max

ε max be the maximum efficiency.

Photo-peak efficiency of whole energy of γ in single Ge detector
Ø Absolute photo-peak efficiency (0.11%@1.17MeV
for 1 crystal) was measured using 60Co (1.17,1.33MeV).
ØRelative efficiency values were measured using
35Cl(n,γ)36Cl. Thus, the detection efficiency from
0.5 MeV to 9 MeV is well understood with ±7%
accuracy.

N sig
I=ε

where Nsig is the number of signals and ε is theefficiency.
Nsig can be written as N sig = N raw − BG
where Nraw be the total number of raw events andBG be the background events.
Nraw was evaluated by the summation of counts inthe channel interval {Cch-3×FWHM, Cch+3×FWHM},
where Cch was the channel of the peak center andFWHM was the full width at the half maximum of theγ-ray photo-peak.

Counts[1/keV]

3. Measurement Relative Intensity of Discrete γ-rays
Intensity can be written as

22.51±0.12

Peak Energy
In [keV]rL =Relative Intensity [%]N1( A ) = β T η Aε1( A ) (1− CγA2 η Aε 2A )NNDC2010(Shibata et.al)

Relative intensities of γ-rays from the 157Gd(n ,γ)158Gd reaction

Energy spectrum of 60Co

Number of events of both the detectors

IAEA
1991

Ratio (Data/Table value)Ge

2.1. Experimetal Data

NNDC
CapGam268.71±0.62 246(15)18.99±0.05257(22)349.42±2.2
12.22±0.0434.3(32)
36.87±0.1
Ratio (data/Table value) for 36Cl
2
1951.1+1959.4
301.61±1.10 317.10±0.94 308(18)2676
16.50±0.51 16.17±0.19
1.52863
55.12±0.66 55.27±0.142975
10.30±0.42 11.41±0.04
13061
30.59±0.54 34.25±0.09 35(3)3428
8.10±0.50
8.29±0.04
Ratio-CapGam
0.539819.36±0.45
10.11±0.08
Ratio=(NNDC-2010)
Ratio-IAEA
4440
12.09±0.57 11.41±0.0404979
31.80±0.79 37.47±0.1302000
4000
6000
8000
10000
Gamma Energy in [keV]5517
15.11±0.76 17.07±0.08
5715
52.28±1.04 55.27±0.21 51.4(42)5902.7+5913.3
9.98±1.90
11.33±0.04
6110
219.48±1.51 200.41±0.75 197(16)Ø Our data agree fairly well withtable value of NNDC
6619.6+6627.8+6642.0 114.85±1.21 123.44±0.6 127.4(76)

ANNRI detector

Experimental Setup:
p Neutron beam line at J-PARC/MLF.
p High intensity pulse neutron beam.
p ΔEn/En~1%, p beam power 300 kW.
p ANNRI detector is used for measuring γ-rays.

MLF(Our Data)

786.30+788.42
247.81±0.931131
16.39±0.481162.73+1164.86+1170.
94
285.29±0.97132713.15±0.53
1601
35.39±0.59

Reliable Gd(n,γ) MC is needed for neutrino detection experiments.

2. Experiment at ANNRI / J-PARC

Relative Intensities, IR(%)

Peak Area
BG

Relative intensity can be written as

IR =I Norm

199
296
625
780
840
897
959
9699881009
1039
1065
1156!
1186
1230
1277
1366
1420

100.00±0.23
6.31±0.17
2.62±0.10
2.75±0.12
3.11±0.10
1.30±0.11
6.61±0.10
5.57±0.09
4.38±0.10
2.33±0.10
10.43±0.11
20.23±0.1136.56±0.14
15.57±0.11
9.43±0.09
5.71±0.09
4.17±0.11
2.16±0.10

1449
1604
1681
1962
2211
5348
5660!
5836!
5918!
6034!
6348!
6429!
6481!
6870!
7288!
7382!

Relative
Intensity,IR[%]
MLF(our data]

4.33±0.09
1.25±0.08
3.94±0.11
5.24±0.12
2.94±0.11
0.75±0.06
1.07±0.050.89±0.05
0.93±0.06
1.65±0.05
1.55±0.05
0.94±0.05
0.97±0.04
1.13±0.04
2.16±0.04
4.33±0.03

4. Summary

Energy in [keV]IØT h e r e l a t i v e i n t e n s i t i e s o f
discrete γ-rays from then-capture with 155Gd reaction
have been calculated for the firsttime with good accuracy.

RelativeIntensity,
IR [%]
Peak Energy[in keV]MLF[Our data] Peak Energy[in keV]

×100%

Where I be the intensity of any
photo-peak and Inorm be the valueof intensity by which we makenormalized.

ØIn this experiment, we measured the discrete γ-rays from the 155,157Gd(n,γ)
reactions using ANNRI detectors (Ge detectors) with good energy resolution.
ØThe good agreement between our data and NNDC table value (CapGam) of
35Cl(n,γ)36Cl and 158Gd in discrete levels.
ØThe relative intensities of discrete γ- rays of 156Gd was calculated for the first timewith so much good accuracy.
ØNext we need to estimate the systematic errors due overlap and leakage effect of
γ-rays through the detectors to establish the result .

rdThe 3 KMI International Symposium on “Quest for the Origin of Particles and Universe”

Nagoya University , ES Hall, January 5-7, 2017, Nagoya, Japan