Laser Induced Breakdown Spectroscopy (LIBS) based wall monitoring diagnostic for ADITYA-U tokamak

Understanding and controlling plasma-wall interactions (PWIs) are crucial for tokamak performance and longevity, as PWIs significantly influence fuel retention, impurity deposition, and plasma stability. Conventional diagnostics like Residual Gas Analysis and optical emission spectroscopy are limited; they lack direct, in-situ insight into surface-bound impurities and often require plasma presence or vacuum venting. Laser Induced Breakdown Spectroscopy (LIBS) is a promising solution for in-situ analysis of plasma-facing components (PFCs), offering direct, remote detection of elemental compositions on PFC surfaces without sample removal or complex preparation.

We have developed a LIBS-based wall-monitoring diagnostic system for the ADITYA-U tokamak, featuring a high-energy pulsed Nd:YAG laser, dedicated optics, a Czerny-Turner spectrograph, and a motorized sample holder. Complementing this, an ex-situ LIBS setup enables laboratory validation and detailed analysis of materials exposed to plasma discharges. By comparing spectra from exposed and control samples, we study the composition and depth of plasma-modified layers.

The in-situ LIBS system will be deployed in upcoming ADITYA-U campaigns, providing a comprehensive framework for monitoring fuel retention, impurity deposition, and assessing wall conditioning methods. This work advances diagnostic capabilities for next-generation fusion reactors.