Monte Carlo simulation of the neutron measurement for the Large Helical Device deuterium experiments

The Large Helical Device (LHD) plans to start deuterium experiments in March 2017. The expected performances of the neutron flux monitor and the vertical neutron camera have been investigated by neutron Monte Carlo simulations using the MCNP-6 Monte-Carlo neutronics code and the cross-section library FENDL-3.0. Three neutron flux monitors using U-235 fission chambers are located on the center axis of LHD and at two toroidal locations on the horizontal plane outside the cryostat. The detection efficiency for the neutron emission in the plasma has been evaluated. This is almost insensitive to the neutron source profile and the plasma position. The vertical neutron camera consists of 11 channels of stilbene detectors with a parallel collimator embedded in the concrete floor slab. The response function of the stilbene detector has been evaluated with PHITS code. Based on the response function, the count rate of the stilbene detector is estimated to be similar to 6 x 10(4) cps for maximum neutron yield shots. Also, the spatial resolution is estimated to be 70 mm, which is smaller than the pitch of adjoining channels. (C) 2017 Elsevier B.V. All rights reserved.