Preliminary Experiments to Develop a He-W Calibration Standard Using Laser Induced Breakdown Spectroscopy*

To address the needs of future fusion reactors, laser based diagnostic techniques for plasma-material interactions (PMI) are being developed at ORNL. Laser-induced breakdown spectroscopy (LIBS) is a technique for measuring elemental surface composition, and is a possible diagnostic for characterizing elemental concentrations in plasma-facing materials. The purpose of the LIBS system described here is to quantify helium (He) concentration in exposed tungsten (W) targets. To accurately quantify He concentration in situ a calibration stranded must be developed, including extensive calibration of the entire LIBS system. To accomplish this, two LIBS setups were explored: \textit{ex-situ} LIBS and \textit{in-situ} LIBS. \textit{Ex-situ} LIBS experiments used W targets exposed to a He$+$ ion beam to determine laser parameters and calibration settings for in-situ experiments. Results will be discussed. \textit{In-situ} LIBS analysis will be assessed for W targets exposed to He plasma. Preliminary results will be discussed.