実験報告書様式（プロジェクト利用）

MLF Experimental Report

提出日 Date of report
Jan. 2, 2015

実験課題番号 Project No.

装置責任者 Name of responsible person

2008A0048

Kenichi Oikawa

実験課題名 Title of experiment

装置名 Name of Instrument/（BL No.）

Development and Application of Neutron Optical and Detection

BL10Systems

利用期間 Dates of experiments

実験責任者名 Name of principal investigatorJan. 22-23, 2009

Jun-ichi Suzuki

Feb. 12-13, 2009

所属 Affiliation

Feb. 24-26, 2009

J-PARC Center, Japan Atomic Energy Agency

１．研究成果概要（試料の名称、組成、物理的・化学的性状を明記するとともに、実験方法、利用の結果得られた主なデータ、考察、結論、図表等を記述してください。
Outline of experimental results (experimental method and results should be reported including sample
information such as composition, physical and/or chemical characteristics.
The 1 MW spallation neutron source of the materials and life science experimental facility (MLF) is aworld-class neutron source. Therefore, the scattering instruments to be constructed at the facility will be alsoworld-class instruments and it is expected that the instruments will lead frontier sciences. However, there remain
additional possibilities of making their performances higher and giving them functional capabilities by adopting
novel neutron optical and detection systems. In order to realize this idea, we have developed neutron optical anddetection systems and carried out experiments to evaluate them. In JFY2008, we evaluated a neutron beam
monitoring system.
It is required for a monitoring system of the MLF to give lower detection efficiency applicable even for
intense pulsed neutron beams comparing with that of a 3He neutron beam monitor, homogeneous detection
efficiency, and low gamma-ray background. We then carried out the evaluation of nitrogen monitors in the termof commissioning of the NOBORU.
At first, we tried to evaluate a beam monitor purchased from the ILL. The active volume is 220 mm×75 mm
×10 mm. The partial gas pressure of N2 is 700 mbar and the efficiency is 5×10-5. However, we could not get
effective data because a DAQ system of the monitor did not work at the MLF well.
Next, we evaluated a prototype of a beam monitor made with TOSHIBA Electron Tubes & Devices Co., Ltd.
The active volume is 100 mm×50 mm×20 mm. The partial gas pressure of N2 is 600 mbar. We evaluated themonitor at BL10 and also at CHOP in JRR-3 and could obtain the positional dependence of the pulse height
distribution as shown in Fig. 1. The detection efficiency was almost constant along the direction parallel to theanode lines. On the contrary, A drop of the detection efficiency was observed along the direction perpendicular
to the anode lines and between the two anode lines. Considering the experimental results, we changed a design ofthe monitor container and anode and cathode lines in the container and made a new prototype as shown in Fig. 2.

1

１．研究成果概要（つづき） Outline of experimental results (continued).

Fig. 1 A photo of a prototype of a beam monitor and the positional dependence of the pulse height distribution of
the beam monitor measured at CHOP in JRR-3 and at BL10.

Fig. 2 The second prototype of a beam monitor.
Standard design of the monitoring system will be determined with the second prototype and the parameters of
the beam monitor will be optimized by the experiments planned in JFY2009. Those results will be applied to themonitoring systems of various scattering instruments.

必要に応じて、A4 サイズの用紙に続きを記入して下さい。
Please use A4-size papers for further reporting, if necessary.

2