Scaling calculations of optimal liner performance to determine the voltage design configuration in Atlas

Summary form only given, as follows. Atlas is the new pulsed power facility being designed at Los Alamos National Laboratory (LANL) to perform high energy-density experiments in support of weapons physics and basic research programs. At the initial design stage, Marx module "building block" of 120 kV was chosen and there were five possible voltage options, in multiples of 120 kV up to 600 kV. Since the primary mission for Atlas is to hydrodynamic experiments, we search for the best performance in the sense that it produces the highest collision shock pressure with a fixed target as the figure of merit to determine the optimal voltage configuration. Although the bank capacitance and inductance satisfy some simple scaling in bank voltage, the total circuit inductance does not as it depends on the liner radius to be optimized. Furthermore, the condition on voltage reversal to protect the bank circuit also affects the current waveform significantly as we change the voltage. In this investigation we first derived an approximate scaling relation for the current waveform, through its dependence on circuit parameters, as a function of voltage. From this result we could show in general that the optimized liner performance decreases with increasing voltage. Detailed simulations using the 1-D MHD code RAVEN confirm that the optimized liner at 120 kV indeed outperforms the one at 240 kV, but merely by about 10% in shock pressure. But the 240 kV configuration is much more favorable in terms of the radiation source applications, and so it became our final design choice for Atlas. Some physical insights on the Atlas circuit design gained from this study will be discussed.