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
July 26, 2011
装置責任者 Name of responsible person

2010B0029

Dr. Maekawa

実験課題名 Title of experiment

装置名 Name of Instrument/（BL No.）NOBORU /(BL10)

Development of neutron detectors

実施日 Date of Experiment

実験責任者名 Name of principal investigator
Tatsuya Nakamura

Feb 7-9, 2011

所属 Affiliation
Japan Atomic Energy Agency, J-PARC center,
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.
The purpose of the experiment is to develop new types of neutron detectors. An aluminum rod and tin
crystal were irradiated with neutrons to check detector system.

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 types of new detectors were tested in this term. One was a scintillator monitor detector and the otherwas a two-dimensional scintillator detector for “SENJU” instrument.
i) ZnS scintillator monitor detector
A GS-20 glass scintillator detector has been extensively used in the ISIS pulsed neutron facility thanks toits superior temporal response and robustness. On the other hand the glass had to be mechanically processed
into a bead form to decrease a detector efficiency (A detector efficiency usually required in a beam line is in
the order of 10-5.) The initial motivation to develop new scintillator monitor detector was to provide the one
with easy-tuning of the detector efficiency. The anticipated monitor detector, ZnS scintillator mixed with aneutron converter material of low cross section, has a great advantage to adjust detector efficiency. By simply
selecting the proper converter material and controlling the mixed amount the detector efficiency was adjusted
as request. In the demonstrative experiment the detector efficiency was tuned around 10-3 to 10-4, which
was still rather “high” as monitor detector, to save the experimental time. The neutron-sensitive area of thedetector had a size of 50 x 50 mm2 with a layer thickness of 0.1 mm, just enough to cover the beam at BL10.
1Counts/10000shot

2. 実験方法及び結果（つづき） Experimental method and results (continued)
Three detectors were prepared for the test; ZnS/natLi, ZnS/ CaCl2106105104103102indicating the feasibility of those as a beam monitor. These

101detectors exhibited much less detector efficiency as expected;

100GS-20 glass
ZnS/CaCl2

and a GS-20 glass scintillator for reference. Figure 1 shows theZnS/natLi

time-of flight (TOF) spectra measured at the distance of 12.5 mfrom the mercury target. Both the ZnS/natLi and ZnS/CaCl2
detectors exhibited similar TOF spectra to the reference detector,

2.1x 10-3 and 3.4 x 10-4 for the ZnS/CaCl2 and ZnS/natLi,
010000

20000

30000

40000

Elapsed time, μs

respectively. These results demonstrated that the easy-tune ofFigure 1 Time-of-flight spectra measured withZnS/CaCl2, ZnS/natLi and GS-20 glass (reference)monitor detectors.

the detector efficiency by selecting the converter materials andadjusting their amounts. The detector efficiency measured withnatZnS/ Li detector agreed well with the calculated result whilst the ZnS/CaCl2 counted more by a factor threethan expected. This result could be due to the threshold voltage set lower for the ZnS/CaCl2 detector todetect 598-keV proton generated in 35Cl(n,p)35S reaction. The origin of this should be clarified in future.
(2) Beam line detectors for “SENJU” instrument
Three beam line detectors for “SENJU” instrument were successfully tested in this run. The detectors weremanufactured by fully exploiting the scintillator detector technologies developed in the neutron
instrumentation group in JAEA. These detector modules, each of which had 64 x 64 pixels with a pixel size of4 mm, were assembled in a row to mock up one detector bank (Figure 1). All the detector components
including detector electronics (amplifier, encoder, data acquisition boards and even the cables) were identicalto the one to be used in the instrument. The detectors measured neutrons without oscillation for over one
day, confirming the stability of the detector system. Figure 2 and 3
show some of the examples of the measured spectra. The detectors
measured Debye-Scherrer ring of the Al2O3 sample clearly.
Moreover the Bragg peaks of the single crystal Sn were measured
clearly with a descent spatial resolution in a reasonable intensity,
confirming the soundness of the detector system.

Figure 3 Diffraction pattern from an Sn
crystal (tof: 10.0~10.1 ms).

Figure 2 d-spacing of the Al2O3
measured in this test.

Figure 1 Mock-up of the one bank of the“SENJU” instrument assembled in theBL10.

2