Design considerations of the European DEMO's IR-interferometer/polarimeter based on TRAVIS simulations

TL;DR

This paper discusses the design considerations for the IR-interferometer/polarimeter in the European DEMO fusion device, using TRAVIS simulations to analyze measurement accuracy and propose a geometry for vertical position control during plasma ramp-up.

Contribution

It introduces a TRAVIS-based ray tracing simulation including relativistic effects and proposes a measurement geometry for improved plasma position control in DEMO.

Findings

Measurements over-estimate plasma density by up to 20%

Proposed geometry enables vertical position control during ramp-up

Relativistic effects significantly impact measurement accuracy

Abstract

Interferometry is the primary density control diagnostic for large-scale fusion devices, including ITER and DEMO. In this paper we present a ray tracing simulation based on TRAVIS accounting for relativistic effects. The study shows that measurements will over-estimate the plasma density by as much as 20 degree. In addition, we present a measurement geometry, which will enable vertical position control during the plasma's ramp-up phase when gap-reflectometers and neutron cameras are still blind.