Plasma-wall interaction in the Spanish stellarator TJ-II.: Diagnostics and first results

First plasmas have been produced in the Spanish stellarator TJ-II. They have been generated by 250 kW ECR heating under all metal wall conditions. Two different magnetic configurations, corresponding to similar iota values but different plasma volumes, have been used. Helium glow discharge conditioning has been systematically applied previous to and between discharges. Good plasma start-up performance has been obtained, characterised by a short delay respect to the gyrotron pulse and controlled peak value of the electron density. The present results stress the important role that plasma-wall interaction phenomena are expected to play in the generation and optimisation of TJ-II plasmas in future campaigns. (C) 1999 Elsevier Science B.V. All rights reserved.