Unusually stable hot electron ring in a hot electron plasma confined in a magnetic mirror

A ring of highly energetic electrons formed in close proximity to conducting walls in a simple magnetic mirror has been observed. The ring is stable at pressures below the Guest-Harris criterion and in the absence of line tying to the end walls. The ring is observed to be stable only when it is formed in close proximity to conducting side walls. A series of experiments in which the ring was forced away from the wall is described. In each case the ring became grossly unstable. Two stabilizing mechanisms in which image charges and currents play a dominant role are suggested