Experimental studies on generation and behaviour of field-reversing E- and P-layers

Recent results are reported from the Cornell RECE-programme studying the generation and stability of field-reversing electron and ion rings for Astron or Spherator-type devices. Most important, field-reversing electron rings with field-reversal lasting over 220 μs and overall lifetimes up to 1.3 ms were obtained in the new RECE-Christa facility using 2.5-MeV electrons. The ring decay generally is smooth and roughly consistent with a collisional diffusion of the fast electrons in the background gas, except when the toroidal field, Btheta, is permitted to decay too rapidly. Experiments on the smaller RECE-Berta facility show precessional stabilization of weak rings when magnetic multipole Ioffe fields are applied. Experiments using magnetically insulated diode arrangements and microsecond voltage pulses resulted in the generation of intense ion beams with pulse lengths up to 1 μs and current densities up to 30 Acm-2. (author)