Fast simulations for large aspect ratio stellarators with the neoclassical code KNOSOS

TL;DR

This paper introduces an enhanced version of the KNOSOS code, enabling fast and accurate neoclassical simulations for large aspect ratio stellarators, including effects often neglected by standard codes, demonstrated on Wendelstein 7-X.

Contribution

The new KNOSOS version extends applicability to any large aspect ratio stellarator and includes additional physical effects, improving simulation accuracy and efficiency.

Findings

Able to simulate any large aspect ratio stellarator

Includes magnetic drift tangent component and flux-surface potential variation

Demonstrated performance on Wendelstein 7-X configuration

Abstract

In this work, a new version of KNOSOS is presented. KNOSOS is a low-collisionality radially-local, bounce-averaged neoclassical code that is extremely fast, and at the same time, includes physical effects often neglected by more standard codes: the component of the magnetic drift that is tangent to the flux-surface and the variation of the electrostatic potential on the flux-surface. An earlier version of the code could only describe configurations that were sufficiently optimized with respect to neoclassical transport. KNOSOS can now be applied to any large aspect ratio stellarator, and its performance is demonstrated by means of detailed simulations in the configuration space of Wendelstein 7-X.