A conservative approach to scaling magneto-inertial fusion concepts to larger pulsed-power drivers

Abstract

The Magnetized Liner Inertial Fusion (MagLIF) experimental platform [M. R. Gomez et al., Phys. Rev. Lett. 113, 155003 (2014)] represents the most successful demonstration of magneto-inertial fusion (MIF) techniques to date in pursuit of ignition and significant fusion yields. The pressing question remains regarding how to scale MIF concepts like MagLIF to more powerful pulsed-power drivers while avoiding significant changes in physical regimes that could adversely impact performance. In this work, we propose a conservative approach for scaling general MIF implosions, including MagLIF. Underpinning our scaling approach is a theoretical framework describing the evolution of the trajectory and thickness of a thin-walled, cylindrical, current-driven shell imploding on preheated, adiabatic fuel. By imposing that scaled implosions remain self-similar, we obtain a set of scaling rules expressing key target design parameters and performance metrics as functions of the maximum driver current Imax. We identify several scaling paths offering unique, complementary benefits and trade-offs in terms of physics risks and driver requirements. Remarkably, when scaling present-day experiments to higher coupled energies, these paths are predicted to preserve or reduce the majority of known performance-degrading effects, including hydrodynamic instabilities, impurity mix, fuel energy losses, and laser-plasma interactions, with notable exceptions clearly delineated. In the absence of α heating, our scaling paths exhibit neutron yield per-unit-length scaling as Ŷ∝[Imax3,Imax4.14] and ignition parameter scaling as χ∝[Imax,Imax2.14]. By considering the specific physics risks unique to each scaling path, we provide a roadmap for future investigations to evaluate different scaling options through detailed numerical studies and scaling-focused experiments on present-day facilities. Overall, these results highlight the potential of MIF as a key component of the national ignition effort.

Exploring the Parameter Space of MagLIF Implosions using Similarity Scaling

“…As originally demonstrated in Ref. 29, we then show that MagLIF loads can be incompletely similarly scaled, meaning that the experimental input parameters of MagLIF can be varied such that many but not all of the dimensionless quantities characterizing a MagLIF implosion are conserved. Following arguments based on similarity scaling, we can then estimate the performance of scaled MagLIF loads when using this framework.…”

“…As discussed in Ref. 29, the MRT modes that most decrease the amount of pdV work done on the fuel and reduce confinement are those that maximize the perturbations at the liner interior surface. When accounting for MRT feedthrough, one can estimate the number of e-foldings of the most dangerous MRT modes during the acceleration phase of the implosion: 29…”

“…As a side note, it is common to describe imploding zpinch liners as thin shells. 29,36 The thin-shell model can be readily retrieved by summing Eqs. (19) and (20) and approximating R(t) R out (t) R in (t).…”

“…It characterizes the pushback done by the fuel on the imploding liner. 29 To increase Φ relative to Π, one clearly needs to increase the preheat per-unit-length…”

Performance Scaling in Magnetized Liner Inertial Fusion Experiments

“…Previous experience with other Z-pinch fusion concepts [41,42] as well as analytic arguments [43] suggests that the yield should scale roughly as peak current to the fourth power, which initially appears to be inconsistent with these results. However, without any other changes, increasing peak current should also produce a higher CR, and the observed CR did not significantly change between the high-and low-current cases (Fig.…”