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
Oct 31, 2013
装置責任者 Name of responsible person
Dr. Oikawa

2012A0131

実験課題名 Title of experiment

装置名 Name of Instrument/（BL No.）

Development of neutron scintillation detectors

NOBORU /(BL10)

実験責任者名 Name of principal investigator

実施日 Date of Experiment

Masaki Katagiri

Apr 26-28, 2012, May 10-12, 2012

所属 Affiliation

May 22-25, 2012

Ibaraki University, Frontier Research Center for Applied AtomicSciences
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.
In this allocated experimental time the detector performances of (i) neutron monitor detectors using ZnS
scintillator, and (ii) a new developed iBIX detector were evaluated.
(i) Scintillator monitor detector
We have developed already some kinds of ZnS monitor detectors with neutron converter materials that arenat

LiF, 11B2O3 and CaCl2. But, the detector efficiency was tuned around 10 -2 to 10-3 which was still rather “high”

as monitor detector. Therefore, we developed a new scintillator monitor detector that has the efficiency of around10-4 like a comercial 3He neutron monitor. The developedmonitor detector used only ZnS phosphor that has32S(n,)28Si and 33S(n,)29Si reaction for neutron. The

cross sections are around 10-2 burn with naturalabundance.

Figure 1 shows photograph of the newneutron monitor detector composed of a reflected body, ascintillator

andtwophotomultipliers.

The

neutron-sensitive area of the detector had a size of 50 x 50
mm2 with a layer thickness of 0.05 mm, just enough tocover the beam at BL-10. Figure 1 shows the photographof the prototype detector.

Figure 1 Photograph of a new ZnS monitor
detector

12. 実験方法及び結果（つづき） Experimental method and results (continued)
800

70500

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3020020100

101000Counts for 28-30ms

60

ZnS monitor counts

28-30ms

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ZnS monitor
BL-10 gas monitor

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0000204060

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BL-10 gas monitor counts

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Counts for 8-10ms

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8-10ms040000

TOF time, s

Pulse height, channel

Figure 3 Time-of-flight spectra measured the ZnS
monitorFigure 2 Pulse height spectrum measured the ZnS
monitorAt first, pulse height spectrums of ZnS phosphor shown in Fig.2 were measured. The alpha rays, 28Si and 29Si
based on (n, ) reactions were measured. Discrimination level was set at channel 10 to reject electronics noise.
Figure 3 shows time-of flight (TOF) spectra measured at the distance of 12.5 m from the mercury target. The(Å) is obtained by TOF(s)/3160. The detector efficiency was evaluated as 3x 10-4. The result demonstrated thefeasibility of the detector. Gamma-ray sensitivity is less than 10-6 because the sensitivity of ZnS phosphor is very
low. The detector efficiency can be easily adjusted by the amount of ZnS phosphor.
(ii) Evaluation of a new position-sensitive scintillator detector developed for iBIX
Position-sensitive scintillator detectors with a high spatial resolution were newly developed for the iBIX 16detectors fabricated based on a proto-type
detector and installed in the BL-03 by the endof FY2012. The detector performances of theproto-type

position-sensitive

scintillator

detector were evaluated by using the BL-10
beam line. Figure 4 shows photograph of thedeveloped proto-type iBIX detector.
The present detector has a neutron-sensitive

Figure 4 Photograph of a new iBIX detector

area of 132 x 132 mm2 with a pixel size of 0.5 x 0.5 mm2. The detector technology using WLS fibre readout has
been greatly improved after three years since the first iBIX detector was developed. This would include thedetector efficiency, multi-count characteristics and counting rate characteristics thanks to the increased lightyield collection efficiency and to the newly developed

30000

Photon: 4
Coincidence time: 3sY axis
Collimator: 1.0mm

10ZnS/ B2O3 scintillators. The detector structure, fiber
25000

arrays sandwiched with the two scintillator screens,remained the same as in the first original iBIX detector. In
efficiency, special resolution, counting rate characteristics
were evaluated as a function of time-of-flight. One of theCounts

the experiments of detector performances such as detector

20000
15000
FWHM: 1.10mm
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most important performances for the iBIX is position
resolution. Figure 5 shows the performance of position
resolution which is 1.1mm FWHM in case of irradiationof 1.0mm collimated beam. The intrinsic position
resolution is about 0.6mm FWHM.

50000051015202530Position, x0.5mm

Figure 5 A spatial response of the detector witha 1-mm diameter beam2