Wall Conditioning at the Starting Phase of LHD

Abstract

The first results on wall conditioning in the first and second campaign of LHD experiments are described. By confirming device integrity, operational reliability, and environmental safety, LHD has been successfully started up with intensive discharge cleaning without doing high-temperature baking. Evacuation of about 100 molecular layers of surface contaminants is found to be the key to start up the target plasma by ECH for NBI injection. Importance of combination between mild baking, GDC, ECR-DC and main shots is experimentally confirmed.