Reversed‐field configuration generated by a rotating relativistic electron beam

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 (ΔB z ) and azimuthal (B ϑ) 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, ΔB z remains constant for 5 μsec until B ϑ becomes small, at which time the plasma collapses radially. The observed decay times of 4 μsec and concurrent increase in T e (from 5 to 10 eV) are consistent with classical dissipation of the induced currents.