Electron plasma confinement in a partially toroidal trap

A new experiment seeks to examine equilibrium, stability, and confinement properties of toroidal electron plasmas. Electron plasmas with density about 3×106 cm−3 are trapped for ∼100 μs in a “partially” toroidal (or “C”-shaped) trap (B≈200 G). Large amplitude oscillations are observed in the 100 kHz frequency range. The oscillation frequency is proportional to 1/B and depends on the applied horizontal electric field, but not on the amount of charge in the trap. Some evidence points toward the ion resonance instability as the cause of these oscillations.