High bootstrap current ICRH plasmas in JET

Abstract

High poloidal beta plasmas with a correspondingly high bootstrap fraction of 70+or-15% have been produced using ion cyclotron resonance heating, in an ELM free H mode confinement regime. This regime is terminated by a large edge instability, causing a reversion to L mode confinement. Possible causes for this instability are discussed and the overall implications of the results for steady state bootstrap dominated operation are examined