Reversed field geometry generated with a rotating e-beam

A reversed magnetic field configuration has been produced by injecting a rotating relativistic e-beam (1.2 MeV, 50 kA) along a 1.8 kG guide field into 85 μ, neutral H
₂
(Typically, T
_e
=5 eV, n
_e
=5×10
¹⁵
cm
^-3
). End-on photography, radial scans with Thomson scattering, and CO
₂
interferometry are in agreement with an MHD equilibrium model fitted to measurements of the excluded flux and the beam-induced axial (ΔB
_z
) and azimuthal (B
_θ
) fields. The resulting magnetic field configuration is similar to a belt pinch, with cross-section length-to-width ratio of 20, and midplane β≈.5. The absence of hard x-ray emission after beam passage shows these fields are induced by plasma currents, rather than trapped beam electrons. After beam passage, ΔB
_z
remains constant until B
_θ
becomes small, at which time the plasma collapses radially as ΔB
_z
decays. No unstable motion is observed. The observed decay times of 3-4 μsec, and concurrent two-fold increase in T
_e
(obtained from H
_β
line-to-continuum data) are consistent with classical dissipation of the induced currents.