Electrostatic End-Plugging of a Plasma in a Cusp-Shaped Magnetic Field Composed of a Magnet Array

An end-loss of a plasma through a cusp-shaped magnetic field is experimentally investigated to be plugged by an electrostatic potential barrier. The main plasma is contained in a surface magnetic field whose one end is of cusp geometry. The potential barrier is set up near the cusp region by a production of another independent plasma whose space potential is controllable. The effects of the potential barrier on the end-plugging are studied with a measurement of the decay time of an after-glow plasma. It is observed that the decay time is improved by 2 ~ 3 times longer than that without the potential barrier. The experimental results are found to be consistent with preliminary estimated values.