Reversed-field configuration generated by a rotating relativistic electron beam

Abstract

A reversed-field plasma confinement geometry has been produced by plasma currents induced by a rotating relativistic electron beam injected into 85 mTorr neutral hydrogen. The resulting belt-pinch-like configuration has a rectangular cross section, with length-to-width ratio of 20, and midplane β=0.5. An equilibrium model, fitted to measurements of the excluded flux and induced axial (ΔBz) and azimuthal (Bϑ) magnetic fields, is in agreement with the annular plasma observed with radial Thomson scattering scans, CO2 interferometry, and end-on streak photographs. After beam passage, ΔBz remains constant for 5 μsec until Bϑ becomes small, at which time the plasma collapses radially. The observed decay times of 4 μsec and concurrent increase in Te (from 5 to 10 eV) are consistent with classical dissipation of the induced currents.