実験報告書様式（一般利用課題・成果公開利用）

MLF Experimental Report
課題番号 Project No.

提出日 Date of Report
June 8, 2017
装置責任者 Name of responsible person
Dr. K. Oikawa

2014B0246

実験課題名 Title of experiment

装置名 Name of Instrument/（BL No.）

Development of neutron scintillators and detectors with them
実験責任者名 Name of principal investigator

NOBORU /(BL10)
実施日 Date of Experiment

Masaki Katagiri

Dec 17-20, 2014, Apr 16-18, 2015

所属 Affiliation

Apr 15-16, 2016, Apr 22-23, 2016

Ibaraki University, Frontier Research Center for Applied Atomic

May 16-17, 2016

Sciences
試料、実験方法、利用の結果得られた主なデータ、考察、結論等を、記述して下さい。（適宜、図表添付のこと）
Please report your samples, experimental method and results, discussion and conclusions. Please add figures andtables for better explanation.
1. 試料 Name of sample(s) and chemical formula, or compositions including physical form.
No sample was used in the experiment. The detector performances were purely evaluated using a collimatedpulsed neutron beam only.

2. 実験方法及び結果 （実験がうまくいかなかった場合、その理由を記述してください。）
Experimental method and results. If you failed to conduct experiment as planned, please describe reasons.
Two research themes were evaluated in this term. One is new ZnS/6LiF scintillators of a two-dimensional
scintillator detector for “iBIX” instrument and the other is a scintillator-type neutron monitor.
(i) Evaluation of new ZnS/6LiF neutron scintillators
We have developed new ZnS/6LiF neutron scintillators for iBIX-type detectors using wavelength shifting fiber
readout method. Two kinds of scintillators, namely, a front-side scintillator and a rear-side scintillator are used
for these detectors. The former is set on front of a crossed WLS fiber bundles and the latter on the rear. The
front-side scintillator requires a good detection efficiency for wide-wavelength neutrons. The rear-side
scintillator requires a high detection efficiency for short wavelength neutrons to detect effectively neutrons
passed from the front-side scintillator. In this scintillator, neutrons are irradiated to surface of the scintillator.
Therefore, we evaluated the front-side and rear-side scintillators fabricated with a new polymer-type adhesivematerial under several conditions.
1010Wemeasuredcounting-rate
Front side scintillator
Rear side scintillatorcharacteristics of the scintillators
as a function of time-of-flight at
the distance of 12.5 m from the1010
mercury target after a scintillator
ZnS/ LiF
ZnS/ LiF
sample was attached on the front
400/480
400/480 Glue A
720/600
500/600 Glue A
864/720or the rear of the crossed WLS
600/720 Glue A
B2O3 standard
B2O3 standard
10fiber bundles of an iBIX-type
1002468100
246810
Wavelength of neutron,Adetector. Figure 1 and 2 show
Wavelength of neutron,AFig.2 Dependency of counting-rate
dependencyofcounting-rate
Fig.1 Dependency of counting-rate curves for the rear-side scintillator
curvesforthefront-side
curves for the front-side scintillator on the amount of mixture
scintillator and the rear-side
on the amount of mixture
4Counting rate, cps

Counting rate, cps

4

3

6

3

6

2

2oo

1

2. 実験方法及び結果（つづき） Experimental method and results (continued)
scintillator on amount of the mixture. The
1010detection characteristics of the front-sideZnS/ LiF
ZnS/ LiF
600/720400/480
scintillators are nearly unchanged with increasing
the amount of mixture and the detection1010characteristics of the rear-side scintillators
Adhensive material
Adhensive material
1mg/cm21mg/cm2
improves in short wavelength region with2mg/cm22mg/cm23mg/cm23mg/cm24mg/cm24mg/cm2
increasing the amount of mixture. By these
101002468
1002468
10results, a thin scintillator was selected as theWavelength of neutron,AWavelength of neutron,Afront-side scintillator and a thick scintillator as
Dependency
ofFig.3
Dependencyof Fig.4
the rear-side scintillator. Figure 3 and 4 showcounting-rate curves for the counting-rate curves for thefront-side scintillator on the rear-side scintillator on thedependency of counting-rate curves for theamount of adhesive material amount of adhesive material
front-side and the rear-side scintillator on amountof the adhesive material. It is confirmed that theamount of 2 mg/cm2 is best for a thin scintillator and the amount of 4mg/cm2 is best for a thick scintillator. By
using these results, we can improve the detection efficiency depending on the thickness of scintillator byoptimizing the amount of the adhesive material.
(ii) Evaluation of a scintillator-type neutron beam monitor
A neutron beam monitor is very important to measure accurately
incident pulsed neutrons in neutron instruments. Especially, a
scintillator-type neutron monitor should be used for high intensity
neutron beams when the power of J-PARC will reach 1MW.
Therefore, we developed a low-sensitive scintillator-type neutron
monitor correspond to a high-counting-rate neutron beam. Figure 5
shows a photograph of a developed neutron monitor. A neutron-sensitiveFig. 5 A developed neutron monitor.
area has a size of 50 x 50 mm2 with a scintillation layer thickness ofabout 0.1 mm on a quartz glass plate. Fluorescence signals emitted from the scintillator are detected by two
photomultipliers and are converted to two electric pulse signals. With coincidence counting of both signals, aneutron monitor signal is produced. We prepared three kinds of scintillators: only ZnS:Ag(4mg/cm2),
ZnS:Ag(4mg/cm2)/natLiF(2mg/cm2) and ZnS:Ag(4mg/cm2)/ natLiF(4mg/cm2). Sensitivities of these scintillator
were measured as a function of time-of-flight. TOF characteristics of sensitivities for three scintillators areshown in Fig. 6. Sensitivities of three scintillators at neutron wavelength of 2.2 Å at BL10 are 1.1x10-4, 2.0x10-4
and 3.7x10-4, respectively. These
10300
sensitivities are better able to deal with
1MW pulsed beam intensity because the250
ZnS only
ZnS+nLiF(50mg)
ZnS+nLiF(100mg)
maximum counting rate of scintillators is10200
several ten times more than the counting
150
rate of gas-type neutron monitors. Figure
10100
ZnS only
7 shows pulse height distributions of
ZnS+nLiF(50mg)
ZnS+nLiF(100mg)
50
developed neutron monitors. It was
1000246810050
100150confirmed that almost every signal in
Wavelength of neutron, APulse height, channel
three scintillators can be counted by aFig.6 TOF characteristics ofFig.7 Pulse height distribution
sensitivities
forthreelow discrimination level. By thesefor three scintillators
scintillators
results, we can easily change thesensitivity by adjusting thickness of thescintillator and amount of the added natLiF.
446

Counting rate, cps

Counting rate, cps

6322oo-2Counts

Efficiency-3-4-523