An optimization study of multi-material-shell gas puff Z-pinches as a pulsed neutron source on the Sandia Z facility

Summary form only given. Previous 1D RMHD studies of deuterium (D) double-shell gas-puff Z-pinches driven by the Sandia ZR accelerator have predicted a substantial increase in thermal fusion neutron yields (∼5×10
¹⁴
vs. ∼3×10
¹³
) if D in the outer shell is replaced with a dense, higher Z, better radiating element. The implosion dynamics of the loads are susceptible to the development of multidimensional structure and nonuniform gradients due to the RT instabilities, all of which can lower the neutron yield. Furthermore, a preliminary 2D RMHD analysis of the same gas puff loads, examined in above 1D studies, indicates a complex interaction dynamics between the higher-Z outer shell material and the inner shell D, wherein the break-through and penetration of the outer shell material and subsequent push-out of the interior D matter adversely affects the neutron yield. In this study, we present the results from numerical simulations of multi-shell gas puff Z-pinch loads composed of argon and D using the multiphase version of the Mach2+DDTCRE 2D RMHD code. We focus on understanding and controlling the interaction dynamics of the argon and D in order to optimize the neutron yield. We examine the neutron yield performance of a variety of Ar/D multi-shell gas puff nozzle load configurations by varying the mass distribution and composition. A comparison of the results with 1D predictions and with pure D loads is made as well.