# Drift and Separation in Collisionality Gradients

## TL;DR

This paper investigates a collisionality-gradient-induced drift in plasma particles, revealing its dependence on mass and energy, and proposes a novel mass-separation method based on this drift.

## Contribution

It introduces a new understanding of particle drift due to collisionality gradients and proposes a mass-separation scheme leveraging this effect.

## Key findings

- Drift reduces to impurity pinch at high Z.
- Drift magnitude depends on particle mass and energy at low temperatures.
- Proposed separation scheme's effectiveness varies with collisionally dissipated energy.

## Abstract

We identify a single-particle drift resulting from collisional interactions with a background species, in the presence of a collisionality gradient and background net flow. We analyze this drift in different limits, showing how it reduces to the well known impurity pinch for high-Z i impurities. We find that in the low-temperature, singly-ionized limit, the magnitude of the drift becomes mass-dependent and energy-dependent. By solving for the resulting diffusion-advection motion, we propose a mass-separation scheme that takes advantage of this drift, and analyze the separative capability as a function of collisionally dissipated energy.