Measurement of Cross-Magnetic-Field Heat Transport in a Pure Ion Plasma

Cross-magnetic-field heat transport in a quiescent pure ion plasma is found to be diffusive and to be dominated by long-range collisions with impact parameters up to a Debye length. The measured thermal diffusivity χ agrees within a factor of 2 with the long-range prediction χL0ex0ex=0ex0ex0.49nv̄b²λD² over a range of 10³ in temperature, $50$ in density, and 4 in magnetic field. This thermal diffusivity is independent of magnetic field strength, and is observed to be up to 100 times larger than the classical diffusivity. These long-range collisions are typically dominant in unneutralized plasmas, and may also contribute to electron heat transport in neutral plasmas.