E-beam heating of a mirror confined plasma as a function of the diode geometry and the magnetic field at the diode

We have investigated the heating of a mirror confined plasma, n_p ~ 10¹³ - 5·10¹⁴, by a relativistic electron beam with the following parameters: .9-1·2 MeV, 80-140 kA, T = 50 ns. The field at the mirror was 3 kG at the minimum and 5 kG at the peak. The beam was launched either at the peak of the field or was compressed by a factor of four (area) just before the mirror. Both foil and foilless diodes were used. Heating was measured by magnetic probes, Thomson scattering and neutral particle analyzer. The beam was diagnosed by a Faraday cup and by an X-ray pinhole camera looking on a target hit by the beam. We found conditions where primarily electrons were heated and conditions for ion heating as well. When the diode was matched to the transmission line, foilless diodes gave stronger heating than foil diodes.