Plasma and Fusion Research

Volume 11, 2405020 (2016)

Regular Articles

Development of Fast-Neutron Directional Detector for Fusion Neutron Profile Monitor at LHD
Eiji TAKADA, Akihiro FUJISAKI, Naoki NAKADA, Mitsutaka ISOBE1,2), Kunihiro OGAWA1,2), Takeo NISHITANI1) and Hideki TOMITA3)
National Institute of Technology, Toyama College, Toyama 939-8630, Japan
1)National Institute for Fusion Science, Toki 509-5292, Japan
2)SOKENDAI (The Graduate University for Advanced Studies), Toki 509-5292, Japan
3)Nagoya University, Nagoya 464-8603, Japan
(Received 22 November 2015 / Accepted 23 January 2016 / Published 4 March 2016)

Abstract

Fast-neutron directional detectors using scintillating optical fibers have been adopted for neutron emission profile measurement in magnetic confinement fusion devices. Because of their benefits of rapid response and directional properties to reduce restrictions on shielding, they are anticipated for installation in the Large Helical Device (LHD) of the National Institute for Fusion Science (NIFS). As described herein, the system design has been re-examined based on the results of recent experiments and simulations. Results show that fast neutrons with high energy of 14 MeV are attenuated by a self-shielding effect of scintillating fiber. Moreover, it has been demonstrated that the scintillation photons are attenuated in several centimeters before reaching the photon detector. The control of the photon transmission efficiency is important to enhance the directional property of the system. Along with reduced effects of the background gamma rays, adopting a thin scintillating fiber is effective. Further evaluation should be conducted to design a detector system considering the detecting efficiency, directional property, and gamma ray effect for application to an actual radiation field of the LHD.

Keywords

neutron measurement, fast neutron directional detector, scintillating optical fiber, large helical device (LHD), design

DOI: 10.1585/pfr.11.2405020

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