Investigation of the possibility of exceeding the Greenwald density limit during ECRH in T-10

In T-10 experiments, attempts were made to significantly exceed the Greenwa ld limit (n) over bar (Gr) during high-power (P-ab = 750 kW) electron-cyclo tron resonance heating (ECRH) and gas puffing. Formally, the density limit ((n) over bar (e))(lim) exceeding the Greenwald limit (((n) over bar (e))(l im)/(n) over bar (Gr) = 1.8) was achieved for q(L) = 8.2. However, as q(L) decreased, the ratio ((n) over bar (e))(lim)/(n) over bar (Gr) also decreas ed, approaching unity at q(L) approximate to 3. It was suggested that the " current radius" (i.e., the radius of the magnetic surface enclosing the bul k of the plasma current I-p), rather than the limiter radius, was the param eter governing the value of ((n) over bar (e))(lim). In the ECRH experiment s, no substantial degradation of plasma confinement was observed up to (n) over bar (e) similar to0.9((n) over bar (e))(lim) regardless of the ratio ( (n) over bar (e))(lim)/(n) over bar (Gr). In different scenarios of the den sity growth up to ((n) over bar (e))(lim), two types of disruptions related to the density limit were observed. (C) 2000 MAIK "Nauka/Interperiodica".