Experiments on turbulent heating and control of plasma shape in tokamaks

Experimental results on turbulent heating in the Triam-1 tokamak are presented, in which single- and double-pulse heating methods are used. Application of the single-current pulse leads to bulk ion heating of the tokamak plasma - without destruction of macroscopic plasma - both for negative and positive polarity of the Ohmic-heating current. The second pulse in the double-pulse method causes an even greater increase in the bulk ion temperature attained by the first pulse. Shaping experiments and a magnetic island in a small non-circular tokamak, TNT-A, are described. Positional instabilities are studied by decreasing the decay index after the plasma current is established. The combined operations of decreasing decay index and rapid increase of plasma current effectively maintain the elongated plasma. A magnetic island (m=3, n=1) is observed by magnetic probes. In Toriut-4 the equilibrium of an elliptic plasma produced by shaping coils has been confirmed by the use of magnetic probes and high-speed photography. An ellipticity of 1.5 is obtained. The effectiveness of passive feedback circuits is consistent with theory. Runaway electron confinement is improved by shaping. The safety factor, qsub(a), of 1.4 is attained. An integral equation to determine the feedback gain is derived. (author)