Electron plasmas in a “partial” torus

Electron plasmas are trapped in a novel “partially” toroidal (or “C”-shaped) trap designed to study issues of equilibrium, stability, and confinement of toroidal nonneutral plasmas. Plasmas with densities as high as 3.3×106 cm−3 are trapped and decay on a 100 μs timescale in a 196 G magnetic field. Successful trapping of dense electron plasmas requires the application of a strong horizontal electric field (5–10 V/cm). The confinement time scales as the 32 power of the magnetic field. Oscillations in the image charge current to a grounded probe have a frequency that is proportional to 1/B and roughly proportional to the vacuum horizontal electric field. However, the frequency is independent of the amount of charge in the trap. Some evidence points toward the ion resonance instability as the driving mechanism for this new toroidal electron mode.