Slab geometry type cold neutron moderator development based on neutronic study for Riken Accelerator-driven compact Neutron Source (RANS)

Baolong Ma,Yoshie Otake,Takao Hashiguchi,Yutaka Yamagata,Yujiro Ikeda,Makoto Teshigawara,Motoki Ooi,Shin Takeda,Yasuo Wakabayashi,Masahide Harada,F Ott,A Menelle,C Alba-Simionesco

doi:10.1051/epjconf/202023104004

Abstract

Cold neutrons with energy less than several meV are good probes for material research, and they have been available on large neutron facilities, whereas it is not commonly available on compact accelerator-driven neutron source. RIKEN Accelerator-driven Neutron Source (RANS) is a pulsed neutron facility which provides thermal neutrons and high energy neutrons at several MeV. We started a project to implement a cold neutron moderator for RANS to broaden cold neutrons applications. A cold neutron moderator system with a mesitylene moderator at 20K and a polyethylene pre-moderator at room temperature in the slab geometry was designed for RANS. So far, the thickness of the pre-moderator and mesitylene have been optimized to get the highest cold neutron flux by using a Monte Carlo simulation code, PHITS. Graphite reflector dimensions were also proven to have significant effect to increase the cold neutron intensity.

Highlights

Cold neutrons are important in neutron scattering investigation for material science because they have suitable energies for materials structure analysis
The slab geometry was taken for RIKEN Accelerator-driven Neutron Source (RANS) cold neutron moderator to couple the neutron production target and the moderator
By adding 10 cm of graphite at neutron emission side, cold neutron intensity could be increased by 14.5%

Summary

Introduction

Cold neutrons are important in neutron scattering investigation for material science because they have suitable energies for materials structure analysis. RANS is an accelerator-based pulsed neutron facility using the 9Be(p,n)9B reaction [7] in a beryllium target with 7 MeV proton injection. The slab geometry was taken for RANS cold neutron moderator to couple the neutron production target and the moderator. To maximize the cold neutron intensity as much as possible, premoderator thickness and mesitylene thickness were optimized by a Monte Carlo simulation, Particle and Heavy Ion Transport code System (PHITS) [8]. The graphite reflector effect on cold neutron intensity was investigated

Overview of RANS

RANS cold moderator design

Thickness optimization

Evaluation of reflector dimension

Conclusions