Effects of Multipole Cusp Field to the Initial Plasma of Theta Pinch

抄録

It is shown that the initial wall hanging current of a theta pinch can be separated from the discharge tube wall by the multipole cusp field. The radial distribution of the azimuthal current was measured by several magnetic probes arranged radially. Under our experimental conditions the plasma current of the initial phase was clearly separated everywhere from a wall at 20 mTorr. The separation was incomplete at higher pressure because of the large reversed field. The average radial magnetic pressure of the multipole field and the condition to separate the plasma current from the tube wall were derived from the simple model that the plasma was the cylindrical column of the perfect conductivity. The experimental results well agreed with the estimation based on this model.