# Helical inward orbits of high-$Z$ impurities

## TL;DR

This paper investigates how helical orbits, driven by plasma rotation mechanisms, can cause high-$Z$ impurity ions to flow inward and accumulate centrally in tokamaks, impacting plasma purity.

## Contribution

It introduces a new understanding of impurity transport via helical orbits caused by rotation and baroclinic effects in tokamaks.

## Key findings

- Helical orbits connect edge and core regions in tokamaks.
- Rotation mechanisms can induce inward impurity flow.
- Implications for impurity accumulation and plasma purity.

## Abstract

In a tokamak the edge and the central region may become connected by helical orbits resulting from the combination of global poloidal rotation and localized radial shifts. The rotation sustained by the Stringer mechanism and the baroclinic effect are able to generate such helical orbit. This can be a contribution to the inward flow and central accumulation of high-$Z$ impurity ions.