Optimized shielding design for the Magnetic Recoil Spectrometer time (MRSt) on the NIF

For successful implementation of the MRSt on the NIF for time-resolved measurements of the neutron spectrum with a time resolution of ~20 ps and accuracy of ~5%, shielding will be required to reduce the neutron and gamma-ray background flux to an acceptable level at the MRSt detector. Expanding upon previous work done by C. W. Wink et al. [1], an MCNP model of the final MRSt design on the NIF was developed to assess the required shielding for a down-scattered-neutron measurement with a S/B > 5. This work accounts for additional and final changes in the engineering design of MRSt and its placement within the NIF target bay. [1] C. W. Wink et al., Rev. Sci. Instrum. 87, 11D808 (2016). The work was supported by DOE, LLNL and LLE.