Comparison of gridded energy analyzer and laser induced fluorescence measurements of a two-component ion distribution

Department of Physics, West Virginia University, Morgantown, West Virginia 26506-6315, USA.
The Review of scientific instruments (Impact Factor: 1.58). 11/2008; 79(10):10F314. DOI: 10.1063/1.2953411
Source: PubMed

ABSTRACT We present ion velocity distribution function (IVDF) measurements obtained with a five grid retarding field energy analyzer (RFEA) and IVDF measurements obtained with laser induced fluorescence (LIF) for an expanding helicon plasma. The ion population consists of a background population and an energetic ion beam. When the RFEA measurements are corrected for acceleration due to the electric potential difference across the plasma sheath, we find that the RFEA measurements indicate a smaller background to beam density ratio and a much larger parallel ion temperature than the LIF. The energy of the ion beam is the same in both measurements. These results suggest that ion heating occurs during the transit of the background ions through the sheath and that LIF cannot detect the fraction of the ion beam whose metastable population has been eliminated by collisions.

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