Laser induced desorption as tritium retention diagnostic method in ITER

Abstract

Measurement and control of long term tritium retention is one of the most critical issues for ITER and future fusion devices. Since the measurement of the hydrogenic retention by post mortem tile analysis becomes more and more difficult in future devices due to active water cooling and tile activation, Laser Induced Desorption Spectroscopy (LIDS) is under development in TEXTOR to provide a tool to measure the tritium inventory in situ without tile removal. The method is based on rapid spot laser heating and consecutive detection of thermally released hydrogen by spectroscopic detection of Balmer line emission. This contribution presents a short overview of the LIDS setup, the laser heating process, the optical detection and data evaluation as well as the application of laser desorption to map the hydrogen content on a TEXTOR ALT limiter tile with erosion dominated areas and deposition dominated areas with thick a-C:H layers in a laboratory setup, demonstrating the ability to create a 2D mapping of the hydrogenic inventory without damaging the substrate.