Thermally excited fluctuations as a pure electron plasma temperature diagnostic

Abstract

Thermally excited charge fluctuations in pure electron plasma columns provide a diagnostic for the plasma temperature over a range of 0.05 < k(B)T < 10 eV. Three different nonperturbative methods have been developed to determine the plasma temperature. The first method fits the near-Lorentzian spectrum of thermal fluctuations near a single weakly damped mode. This method works well where the modes are weakly damped, i.e., when lambda(D)/R-p < 0.3. The second method utilizes the emission spectrum over a broad frequency range encompassing several modes and the nonresonant fluctuations between modes. This method works for long columns with lambda(D)/R-p > 0.2, so that Landau damping is dominant and well modeled by theory. The third method compares the total (frequency-integrated) number delta N of fluctuating image charges on the wall antenna to a simple thermodynamic calculation. This method works when lambda(D)/R-p > 0.2.