Thermally excited modes in a pure electron plasma.

Thermally excited plasma modes are observed in near-thermal-equilibrium pure electron plasmas over a temperature range of 0.05<kT<5 eV. The measured thermal emission spectra together with a plasma-antenna coupling calibration uniquely determine the temperature. This calibration is obtained from the spectra themselves when absorption of the receiver-generated noise is significant, or from kinetic theory. This nondestructive temperature diagnostic agrees well with standard diagnostics and may be useful for expensive species such as antimatter.