SAWTOOTH STABILIZATION WITH ON-AXIS ICRH ON TORE-SUPRA

Velocity anisotropy of the suprathermal population created by heating (essentially ion cyclotron resonant heating ICRH)) is known to influen ce sawtooth stabilization in tokamaks. However, studying such effects requires a realistic description of the hot ion distribution pitch ang le dependence in terms of easily accessible experimental data. Such a description has been obtained for on-axis ICRH on Tore Supra. A simple analytic model, allowing an easy analysis of experimental data, is de veloped and applied to the above mentioned description of on-axis ICRH . It leads to the result that, contrary to common presumption, sawtoot h stabilization with on-axis ICRH is driven by both passing and trappe d hot ions. In Tore Supra discharges, the stabilizing effect of barely passing hot ions is found to be dominant.