The staged Z-pinch as a potential high-gain fusion energy source: Rebuttal to I. R. Lindemuth et al

TL;DR

This paper defends the staged Z-pinch fusion concept by demonstrating that proper boundary modeling confirms high fusion energy gains are achievable, countering previous simulation-based criticisms.

Contribution

It shows that accurate boundary treatment in simulations supports the viability of high-gain staged Z-pinch fusion, challenging prior negative assessments.

Findings

Fusion energy > 1 MJ without alpha heating

Magnetosonic shocks preheat plasma and increase ram pressure

Proper boundary modeling is crucial for accurate simulation results

Abstract

Magneto-Inertial Fusion Technology Inc. has been working on a Z-pinch concept where a high atomic number liner is compressing a fusion fuel (deuterium-deuterium, or deuterium-tritium) target. The viability of this so called Staged Z-pinch (SZP) concept as a potential high-gain fusion energy source has been questioned in a recent publication by Lindemuth et al [1]. The authors attempted to reproduce previously published MACH2 simulation results [2-4] for Z-machine parameters using three different MHD codes: Hydra, Raven and MHRDR. Their conclusion was that "there is no conceivable modification of the parameters that would lead to high-gain fusion conditions using these other codes". Although they used well established MHD codes to check the SZP concept, and correct input current profiles, we show that their Lagrangian formalism was likely not treating the vacuum/liner boundary properly. Proper modeling using Lagrangian, Eulerian or Adaptive Lagrangian-Eulerian (ALE) formalism indeed confirms that fusion energy production > 1 MJ can be expected without alpha heating, and significantly higher if alpha heating is included. It is shown that magnetosonic shocks play an important role in preheating the target plasma and in piling liner mass at the liner/target interface, which substantially increases the ram pressure just before the pinch stagnation time.