SCALING OF RADIATED POWER TO PLASMA CONTAMINATION FOR NEON SEEDED DISCHARGES ON BORONIZED TEXTOR-94

When neon is injected into a tokamak plasma with the aim of reducing t he peak heat flow into the SOL by enhanced edge radiation, both P-rad and Z(eff) increase. The ratio of the incremental P-rad to the increme ntal Z(eff), Delta P-rad/Delta Z(eff), can change on TEXTOR from 0.1 M W to about 2 MW depending on n(e), on T-e(a) and on the transport regi me. The measured Delta P-rad/Delta Z(eff) is higher for I-mode auxilia ry heated (higher diffusion) than for OH discharges (lower diffusion), consistent with model calculations. For I-mode discharges Delta P-rad /Delta Z(eff) is a decreasing function of T-e(a) and it scales approxi mately as n(e)(-2). The I-mode regime on TEXTOR, which displays very g ood energy confinement scaling, can represent, for suitable conditions , a satisfactory compromise between a high tau(E) and not excessive pa rticle confinement.