Description of the fast moving limiter used with T.F.R

Trials were made in view of modifying the conditions of discharge initiation by limiting the plasma radius with using a metal limiter of small surface so as to reduce the plasma-wall interaction in the phase of current build-up. This limiter, 25cm in diameter, is moved along a 10-15 cm path in 10-20 milliseconds. It consists in a 1kg molybdenum plate supported by a carrier driven by a fast jack. The preliminary results obtained with plasma are rather good