Cross-field electron thermal conductivity in an electron-beam–plasma system

The cross-field electron thermal conductivity coefficient, ${\mathrm{\kappa }}_{\mathrm{\perp }}$, in an electron-beam–heated cylindrical magnetoplasma (${\mathrm{n}}_0$∼3×${10}^{11}$ ${\mathrm{cm}}^{\mathrm{-}3}$; ‖${\mathrm{B}}_0$‖=30 G, 120 G; ${\mathrm{V}}_{\mathrm{b}}$=200 V; ${\mathrm{I}}_{\mathrm{b}}$≤2.5 A, ${\mathrm{t}}_{\mathrm{b}}$≤5 μs) is measured. Results are compared with classically predicted values. After beam turnoff, ${\mathrm{\kappa }}_{\mathrm{\perp }}$ approaches within a factor of 3 the classical value, except for the case ${\mathrm{I}}_{\mathrm{b}}$=1.5 A, ‖${\mathrm{B}}_0$‖=120 G. For that case, and during the beam pulses, ${\mathrm{\kappa }}_{\mathrm{\perp }}$ is found to be anomalously high, by up to over 2 orders of magnitude above the classical value.