Second harmonic ICRF heating experiments in Tore Supra

We report recent experiments which have been conducted at reduced field (B0(0)∼2T) in the Tore Supra tokamak. Up to∼7MW of combined ICRF and LH power have been coupled to deuterium plasmas containing ∼5–12% of hydrogen, resulting in values of normalized toroidal beta reaching βN∼1. For this confinement field, the second harmonic layer of the hydrogen ions resonance is located in the vicinity of the magnetic axis by setting the ICRF generator frequency at∼63MHz. The ICRF power is thus expected to be mostly absorbed by second harmonic cyclotron damping, a scenario known to be prone to the development of fast ion tails. Analysis of plasma measurements and preliminary associated modeling are presented, together with plans regarding forthcoming experiments.