AES AND RBS ANALYSES OF TOKAMAK COLLECTOR PROBES - EXPERIMENTAL CONSIDERATIONS

Analyses by RBS and AES of beryllium collector samples exposed to discharges in the Tokamak de Varennes have been made. Good agreement for the total amounts and types of material deposited on collectors oriented in each of three ways was observed. However, analysis of the AES sputter‐depth profile indicated a peaking of the metal near the outer surface of the collectors. This can be explained by a simple model involving sputtering and redeposition during the tokamak discharge. Implications of this model are that the average amount of material deposited on the collectors may not be related directly to impurity concentrations in the plasma. Experimental analysis of material deposited on the collectors must be made with sufficient depth resolution to obtain information about sputter–redeposition activities during plasma discharges. Copyright © 1990 John Wiley & Sons Ltd.