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Abstract. The paper reports results of experimental campaigns on plasma
ohmic heating, performed during 1999-2000 on the spherical tokamak
Globus-M. Later experimental results with tokamak fed by thyristor
rectifiers are presented in detail. The toroidal magnetic field and plasma
pulse duration in these experiments were significantly increased. The method
of stray magnetic field compensation is described. The technology of vacuum
vessel conditioning, including boronization of the vessel performed at the
end of the experiments, is briefly discussed. Also discussed is the
influence of ECR preioniziation on the breakdown conditions. Experimental
data on plasma column formation and current ramp-up in different regimes of
operation with the magnetic flux of the central solenoid (CS) limited to
100 mVs are presented. Ramp-up of the plasma current of 0.25 MA for
the time interval 0.03 s with about 0.02 s flat-top at the toroidal
field (TF) strength of 0.35 T allows the conclusion that power supplies,
control system and wall conditioning work well. The same conclusion can be
drawn from observation of plasma density behavior the density is completely
controlled with external gas puff and the influence of the wall is
negligible after boronization. The magnetic flux consumption efficiency is
discussed. The results of magnetic equilibrium simulations are presented and
compared with experiment.
IAEA 2001
