Gas breakdown in the R-tokamak

Breakdown processes in a tokamak machine being designed for R-project at Institute of Plasma Physics in Japan are studied extensively by using the zero-dimensional numerical simulation code. One-turn resistance of 0.5 mΩ is assumed for the vacuum chamber. It is shown that one-turn voltage of 50 Volt is sufficient to achieve successful breakdown for optimum filling pressure if the error field is less than about 0.1 per cent of the averaged toroidal magnetic field. Effects of pre-ionization on the breakdown are also discussed. (author)