TOKAMAK DEPOSITION PROBE ANALYSIS BY LASER IONIZATION SPECTROSCOPY

Laser analytical methods are used for the determination of surface sod ium impurity distribution on silicon samples. In the first experiments , the spots on the surface of the sample were atomized by ruby laser p ulses and the sodium atoms were selectively ionized by resonant ioniza tion, thus the simple ion detection yielded the sodium surface contami nation density. The second method applies excimer laser ablation, and the generated ions are analyzed and detected by a reflectron-type time -of-flight mass spectrometer. The analytical arrangements are applied for tokamak plasma investigations. Silicon plates as deposition probes located in the edge plasma region are exposed to several tokamak disc harges, which are contaminated by pulsed sodium impurity injections. S urface analysis of the samples enables determining the sodium impurity fluxes in the tokamak edge plasma region, which are characteristic of particle transport properties. The high sensitivity of the method app lying resonance ionization enables the analysis of single discharges, whereas the application of mass spectrometry offers the possibility of detecting several impurity materials.