Analytical edge power loss at the lower hybrid resonance: comparison with ANTITER IV and application to ICRH systems

TL;DR

This paper analytically examines edge power loss at the lower hybrid resonance in tokamaks, compares it with ANTITER IV simulations, and explores mitigation strategies relevant to ITER and DEMO ICRH systems.

Contribution

It introduces an analytical method for calculating edge power loss at the LH resonance and validates it against ANTITER IV, providing new insights into edge power absorption physics.

Findings

Analytical power loss correlates with local radial electric field.

Comparison shows good agreement with ANTITER IV results.

Proposed solutions can reduce edge power absorption in ICRH systems.

Abstract

In non-inverted heating scenarios, a lower hybrid (LH) resonance can appear in the plasma edge of tokamaks. This resonance can lead to large edge power deposition when heating in the ion cyclotron resonance frequency (ICRF) range. In this paper, the edge power loss associated with this LH resonance is analytically computed for a cold plasma description using an asymptotic approach and analytical continuation. This power loss can be directly linked to the local radial electric field and is then compared to the corresponding power loss computed with the semi-analytical code ANTITER IV. This method offers the possibility to check the precision of the numerical integration made in ANTITER IV and gives insights in the physics underlying the edge power absorption. Finally, solutions to minimize this edge power absorption are investigated and applied to the case of ITER's ion cyclotron resonance heating (ICRH) launcher. This study is also of direct relevance to DEMO.