Application of ion diagnostics to control the laser‐induced removal of surface layer of a carbon substrate

Among other methods of detritiation of in‐vessel tokamak components the application of lasers for removal of fuel trapped in co‐deposited layers is under investigation. The paper presents preparation and tests of ion diagnostic methods for on‐line measurement of the amount and characteristics of ablated carbon, hydrogen/deuterium and contaminant species from the graphite target (plate) of the main toroidal limiter of the TEXTOR tokamak. For removal of the surface layer from the graphite limiter plate Nd:YAG laser was used. Determination of the characteristics of laser‐produced ions has been performed by means of ion collectors and an electrostatic ion‐energy analyser. The main ion stream parameters were measured depending on the number of laser shots and the laser power density on the target surface. The properties of modified carbon sample surface were determined with the use of optical methods and compared with the results of the ion measurements.