  We measured Electron Energy Distribution Functions (EEDFs) from below 200 eV
to over 8 keV and spanning five orders-of-magnitude in intensity, produced in a
low-power, RF-heated, tandem mirror discharge in the PFRC-II apparatus. The
EEDF was obtained from the x-ray energy distribution function (XEDF) using a
novel Poisson-regularized spectrum inversion algorithm applied to pulse-height
spectra that included both Bremsstrahlung and line emissions. The XEDF was
measured using a specially calibrated Amptek Silicon Drift Detector (SDD)
pulse-height system with 125 eV FWHM at 5.9 keV.
