Calculating the Charged Particle Stopping Power Exactly to Leading and Next-to-leading Order

TL;DR

This paper introduces a new systematic method called dimensional continuation for calculating the charged particle stopping power in plasmas, achieving exact results to leading and next-to-leading order with minimal error, improving accuracy for plasma physics applications.

Contribution

It presents a novel, systematic approach to compute stopping power to high precision, including the first exact evaluation of the next-to-leading order term in plasma coupling.

Findings

Exact leading order stopping power known since Spitzer.

Next-to-leading order calculated with high accuracy by BPS.

Implications suggest increased ignition thresholds in high energy density experiments.

Abstract

I will discuss a new method for calculating transport quantities, such as the charged particle stopping power, in a weakly to moderately coupled plasma. This method, called dimensional continuation, lies within the framework of convergent kinetic equations, and it is powerful enough to allow for systematic perturbative expansions in the plasma coupling constant. In particular, it provides an exact evaluation of the stopping power to leading and next-to-leading order in the plasma coupling, with the systematic error being of cubic order. Consequently, the calculation is near-exact for a weakly coupled plasma, and quite accurate for a moderately coupled plasma. The leading order term in this expansion has been known since the classic work of Spitzer. In contrast, the next-to-leading order term has been calculated only recently by Brown, Preston, and Singleton (BPS), using the aforementioned method, to account for all short- and long-distance physics accurate to second order in the plasma coupling, including an exact treatment of the quantum-to-classical scattering transition. Preliminary numerical studies suggest that the BPS stopping power increases the ignition threshold, thereby having potential adverse implications for upcoming high energy density facilities. Since the key ideas behind the BPS calculation are possibly unfamiliar to plasma physicists, and the implications might be important, I will use this opportunity to explain the method in a pedagogical fashion.