Forward Modeling of Gamma Reaction History Signatures From Anticipated Deuterium- Tritium Filled MagLIF Implosions on Sandia’s Z-Machine

Abstract

Nuclear reaction history measurements provide a bang time and burn width of inertial confinement fusion (ICF) implosions and are essential for understanding implosion performance to constrain ICF capsule design. When fusion fuel contains Deuterium (D) and Tritium (T) gas, reaction history is informed by measuring the 16.75 MeV gamma rays generated from the D(T, $\gamma $ )5 He reaction. Such DT-based reaction history measurements have not been made on the magnetized laser inertial fusion (MagLIF) platform on Sandia’s Z-Machine due to the lack of Tritium being used. The recent development of ICF implosions with tritiated fuel will open the possibility of measuring the gamma reaction history (GRH) on the Z-Machine. A forward model of the GRH diagnostic on Z (GRH-Z) has been developed using the MCNP6.3 (Monte-Carlo N-Particle (MCNP)) radiation transport code. The model included the Z-Machine geometry of interest to characterize the impact of neutron-induced gamma rays on the DT reaction history measurements. In addition, the impulse response functions of the GRH-Z diagnostic to understand the temporal response of the detector and the minimum yields required to make a reaction history measurement were calculated. This approach also predicted that with T2 gas doping of MagLIF implosions a reaction history may be made for high performance shots >8e12–2.4e13 depending on the chosen threshold for the detector, with a maximum signal to background ratio of 25%. It was found that for long duration ICF implosions, additional collimation will be needed to prevent the neutron-induced gamma rays from modifying the shape of the measured DT reaction history curve.