Simulations of scattered neutrons for the time-of-flight enhanced diagnostics (TOFED) neutron spectrometer on EAST

The time-of-flight enhanced diagnostics (TOFED) neutron spectrometer has been installed in TOFED house, which is a newly-built neutron diagnostic lab outside the EAST experimental hall. The line of sight (LOS) of TOFED is defined by the collimator going through the 150 cm biological shielding wall, which can reduce background neutrons very effectively for the neutron spectral measurements. The Monte Carlo code MCNP5 is used in the simulations to characterize collimation effects and the radiation safety of the new house. The collimator makes neutron flux almost fully perpendicular to S1 detectors. In addition, the proportion of scattered neutrons in the LOS of the TOFED is obtained for the measured spectral data interpretation. The simulation results show that the TOFED house satisfies the requirement for the TOFED operations at EAST and gives a safe environment for personnel access during the EAST operation.