Laser-induced fluorescence characterization of a multidipole filament plasma

A multidipole filament discharge was characterized using sub-Doppler laser-induced fluorescence (LIF). The ion temperature was found to be Ti=0.028±0.007 eV, measured in the center of an argon discharge. This stands in contrast to the much higher ion temperatures, 0.2<Ti<0.5 eV, reported by researchers using gridded electrostatic energy analyzers. The discrepancy is attributed to the energy resolution of the detectors, with the LIF providing more accurate measurements. In another result, the metastable excited-state ion density was found to scale linearly with the electron density and the discharge current under most conditions. This experiment also demonstrates that LIF can be used for basic plasma physics research in multidipole discharges.