Improving the DD and DT nToF environment for the bottom, axial line-of-sight detectors at Sandia National Laboratories' Z Machine Laboratories

Parameters such as neutron yield, ion temperature, and Be-liner areal density can be inferred from neutron time-of-flight (nToF) measurements and are essential to understanding the performance of a MagLIF implosion. It is important the measured signals accurately represent the source conditions. Simulations were performed using the Monte Carlo for N-Particle (MCNP) code to improve the quality of measured signals on the bottom, axial nToF detectors at the Z machine. The present Z-machine and detector shields give rise to significant amount of bremsstrahlung and scattered neutrons being incident on the detectors. This alters the shape of the signal and results in a poor signal-to-noise ratio and unresolved structure. By changing the geometry surrounding the detectors and adding a midpoint collimator the simulations suggest the contributions from neutron scattering and bremsstrahlung can be minimized, lowering the background and improving~the detector signal.