The environment effect on operation of in-vessel mirrors for plasma diagnostics in fusion devices

TL;DR

This paper discusses the impact of environmental factors on in-vessel mirrors used in plasma diagnostics for fusion devices, highlighting the need for testing mirror materials in current tokamaks to understand degradation.

Contribution

It presents the First Mirror Test (FMT) program at JET, aimed at studying mirror material damage and performance degradation in fusion environments.

Findings

Mirror surfaces undergo erosion and re-deposition affecting reflectivity.

Environmental conditions in fusion devices cause mirror performance deterioration.

Testing in current devices helps predict mirror lifespan in ITER.

Abstract

First mirrors will be the plasma facing components of optical diagnostic systems in ITER. Mirror surfaces will undergo modification caused by erosion and re-deposition processes [1,2]. As a consequence, the mirror performance may be changed and may deteriorate [3,4]. In the divertor region it may also be obscured by deposition [5-7]. The limited access to in-vessel components of ITER calls for testing the mirror materials in present day devices in order to gather information on the material damage and degradation of the mirror performance, i.e. reflectivity. A dedicated experimental programme, First Mirror Test (FMT), has been initiated at the JET tokamak within the framework Tritium Retention Studies (TRS).