Performance of upgraded thermal neutron guides with supermirrors at JRR-3

Tamura, Itaru; Suzuki, Masatoshi; Hazawa, Tomoya; Moriai, Atsushi; Hori, Naohiko; Sasajima, Fumio; Soyama, Kazuhiko

Nuclear Instruments and Methods in Physics Research A, 529(1-3), p.234 - 237, 2004/08

https://doi.org/10.1016/j.nima.2004.04.162

Thermal neutron guides at JRR-3 reactor have been upgraded from Nickel mirrors to Ni/Ti multilayer supermirrors. We performed the characteristics experiment of neutron beams transmitted through supermirror neutron guides. Neutron fluxes at the end of the thermal neutron guides were measured by the gold foil activation method on March 2003. We have confirmed that neutron fluxes at the end of thermal neutron guide increases by 6 times. The neutron spectra were also measured at the end of the thermal neutron guides by the time-of-flight method. The wavelength range for the neutron beam is extended and the shorter wavelength neutrons, which had been filtered by the characteristics of curved neutron guides before upgrade, were observed. In this paper, we have performed several Monte Carlo simulation codes using the McStas package in the consideration of the performance of fabricated supermirrors and its alignment errors for the purpose of estimation of instruments performance. We discuss the comparison of the experimental results with results of simulation.

Simulation for developing new pulse neutron spectrometers, 1; Creation of new McStas components of moderators of JSNS

Tamura, Itaru; Aizawa, Kazuya; Harada, Masahide; Shibata, Kaoru; Maekawa, Fujio; Soyama, Kazuhiko; Arai, Masatoshi

JAERI-Research 2003-008, 34 Pages, 2003/03

JAERI-Research-2003-008.pdf:1.62MB

Moderators components of the McStas code have been created for the design of JSNS instruments. Three cryogenic moderators are adopted in JSNS, One is coupled H moderators for high intensity experiments and other two are decoupled H with poisoned or unpoisoned for high resolution moderators. Since the characteristics of neutron beams generated from moderators make influence on the performance of pulse neutron spectrometers, it is important to perform the Monte Carlo simulation with neutron source component written recisely. The neutron spectrum and time structure were calculated using NMTC/JAERI97 and MCNP4a codes. The simulation parameters, which describe the pulse shape over entire spectrum as a function of time, are optimized. In this paper, the creation of neutron source components for port No.16 viewed to coupled H moderator and for port No.11 viewed to decoupled H moderator of JSNS are reported.