Transport and deceleration of fusion products in microturbulence

TL;DR

This paper introduces a novel, efficient method to analyze how microturbulence affects the velocity-space distribution of alpha particles in fusion devices, revealing significant deviations from traditional models that impact plasma heating and pressure profiles.

Contribution

A new technique applicable to trace impurities that enables the calculation of alpha particle distribution evolution under microturbulence effects.

Findings

Microturbulence causes departure from local slowing-down distribution.

Energy distribution of alpha particles can invert due to turbulence.

Alpha heating and pressure profiles are significantly modified.

Abstract

The velocity-space distribution of alpha particles born in fusion devices is subject to modification at moderate energies due to turbulent transport. Therefore, one must calculate the evolution of an equilibrium distribution whose functional form is not known \emph{a priori}. Using a novel technique, applicable to any trace impurity, we have made this calculation not only possible, but particularly efficient. We demonstrate a microturbulence-induced departure from the local slowing-down distribution, an inversion of the energy distribution, and associated modifications to the alpha heating and pressure profiles in an ITER-like scenario.