Experiments on selective removal of helium by an application of radio frequency field

Proof of principle experiments on preferential removal of helium (He) particles using radio frequency (RF) ponderomotive force have been conducted in linear device (NPX) and tokamak (TXTOR-94). In both experiments, the reduction of the helium ion flux was obtained by applying the RF field at the entrance of the scoop in the pump limiter configuration. The enhancement of helium pumping was observed in the frequency ω range of ωCHe<ω<2ωCHe where ωCHe is the angular ion cyclotron frequency of singly ionized helium ion.