The plasma stored energy as a function of input power follows an off-set linear law during ion-cyclotron resonance heating in the JET Tokamak. The behaviour of the experimentally obtained incremental confinement time tau inc of centrally heated ICRH discharges is understood in terms of a local heat transport model, where chi 0 varies as Ip-1/2 and ( chi ) increases as the size of the q=1 surface is increased at higher Ip/Bt or lower qa due to the presence of the sawtooth instability, where Ip is the plasma current, Bt is the toroidal field and qa is the Tokamak safety factor at the plasma edge. With the transient stabilization of sawteeth by central ICRF heating in JET, the authors are also able to assess the effect of sawteeth on confinement and determine the plasma current scaling of tau inc without mixing its dependence on the safety factor. The same model is also used to explain the degradation of tau inc when ICRH power is deposited off-axis.
Overview of ITER physics deuterium-tritium experiments in JET