Asymptotic scaling laws for the stagnation conditions of Z-pinch implosions

In most high-energy-density science schemes, energy is rapidly coupled to a target in a convergent geometry that drives an implosion and elevates its density, temperature, and pressure upon stagnation. The conditions realized at stagnation are connected to those of the in-flight shell, which are primarily determined by the drive pressure, shell entropy, and geometry of the implosion. In contrast to laser-driven spherical implosions, which typically reach a maximum drive pressure early in the implosion that remains constant thereafter, magnetically-driven cylindrical implosions result in a monotonically increasing drive pressure. We theoretically investigate the implications of this difference by analyzing the implosion trajectory in the aspect ratio/ Mach number parametric plane, and find that, while laser-driven shells expand in-flight while maintaining a fixed density at their exterior, magnetic drive results in decreasing thickness and increasing density during the implosion. We discuss the consequences of these trends on implosion performance, including their potential impact on stability and relationships between drive pressure and fusion yield in ICF experiments.

 

Sandia National Laboratories is a multimission laboratory managed and operated by National Technology & Engineering Solutions of Sandia, LLC, a wholly owned subsidiary of Honeywell International Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA0003525.