Impurity Profile Control in JET Plasmas with Radio-Frequency Power Injection
Various experiments have shown that injection of Radio-Frequency (RF) power may generate an outward pinch for impurities, with corresponding flattening of the impurity density profiles. The effect has been found to be more pronounced when the power is applied to electrons rather than to ions and when it is centrally deposited. Therefore, the application of RF power may represent an active means to heal regimes that would otherwise be incline to accumulate impurities. This paper presents the results of Ni (A = 28), Mo (A = 42) Laser Blow Off (LBO) and Ar/Ne puffing experiments, in JET discharges featuring the injection of RF power at ITER relevant collisionality (neff<0.2), aiming at studying the effect of different power levels when Ion Cyclotron Resonance Frequency (ICRF) is applied to electrons either as H Minority Heating (MH), or as Mode Conversion (MC) on 15-18% concentration of 3He. Spectroscopic and Soft X-Ray data have been reconstructed by a 1D Collisional-Radiataive (CR) impurity transport code, to evaluate the diffusion coefficient D and the pinch velocity V.