BEYOND THE BRILLOUIN LIMIT WITH THE PENNING FUSION EXPERIMENT

Several years ago, it was proposed that a dense non-neutral plasma cou ld be produced in a Penning trap. Nonneutral plasmas have excellent co nfinement, and such a dense plasma might produce simultaneously high d ensity and good confinement. Recently, this theoretical conjecture has been demonstrated in a small (3 mm radius) electron experiment, PFX ( Penning Fusion Experiment). Densities up to 35 times the Brillouin den sity (limiting number density in a static trap) have been inferred fro m the observed strong (100:1) spherical focusing. Electrons are inject ed at low energy from a single pole of the sphere. A surprising observ ation is the self-organization of the system into a spherical state, w hich occurs precisely when the trap parameters are adjusted to produce a spherical well. This organization is caused by a bootstrapping mech anism which produces a hysteresis. Observations of energy-scattered el ectrons confirm the existence of a dense spherical focus. (C) 1997 Ame rican Institute of Physics.