Abstract
This work utilizes Doppler-free saturation spectroscopy to measure Doppler-free, Stark broadened spectral profiles for the π-polarization of the HeI 2 1 P → 6 1 D transition in a low density (n e =7×10 10 −2×10 12 cm−3) helium plasma. The measurements were performed in an electron-cyclotron resonance discharge at 23 mTorr with electron density being diagnosed using a combination of Langmuir probe and microwave interferometry techniques. The Doppler-free profiles were observed to be nearly symmetric at n e < 10 11 cm−3 but markedly asymmetric above this transition point. Electron density is extracted from the spectral data via fitting to a spectral model based on quasi-static Stark broadening. The fit results are compared to n e measurements obtained using a combination of Langmuir probe and microwave interferometry techniques. The fit and measured n e are shown to agree within 20% on average. Finally, the quasi-static model is shown to be valid in the low-density regime for 2 1 P → 6 1 D helium transition.
| Original language | English |
|---|---|
| Pages (from-to) | 48-55 |
| Number of pages | 8 |
| Journal | Journal of Quantitative Spectroscopy and Radiative Transfer |
| Volume | 230 |
| DOIs | |
| State | Published - Jun 2019 |
Funding
The authors humbly thank, in no particular order, Chris Marcus, John Caughman, Tam Ha, Steve Combs, Gary Bell, and Phillip Ferguson for their generous assistance, support, and invaluable input. We also thank Evgeny Stambulchik for his illuminating discussions on Stark broadening. This work would not be possible without these individuals and the authors are grateful to all of them. In addition, a generous thanks to the Graduate Assistance in Areas of National Need (GAANN) Fellowship. This work was conducted at Oak Ridge National Laboratory. Oak Ridge National Laboratory is managed by UT Battelle, LLC, for the U.S. Dept. of Energy under Contract No. DE-AC05-00OR22725. This manuscript has been authored by UT-Battelle, LLC under Contract No. DE-AC05-00OR22725 with the U.S. Department of Energy. The United States Government retains and the publisher, by accepting the article for publication, acknowledges that the United States Government retains a non-exclusive, paid-up, irrevocable, world-wide license to publish or reproduce the published form of this manuscript, or allow others to do so, for United States Government purposes. The Department of Energy will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan (http://energy.gov/downloads/doe-public-access-plan). This work was conducted at Oak Ridge National Laboratory. Oak Ridge National Laboratory is managed by UT Battelle, LLC, for the U.S. Dept. of Energy under Contract No. DE-AC05-00OR22725 . This manuscript has been authored by UT-Battelle, LLC under Contract No. DE-AC05-00OR22725 with the U.S. Department of Energy . The United States Government retains and the publisher, by accepting the article for publication, acknowledges that the United States Government retains a non-exclusive, paid-up, irrevocable, world-wide license to publish or reproduce the published form of this manuscript, or allow others to do so, for United States Government purposes. The Department of Energy will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan ( http://energy.gov/downloads/doe-public-access-plan ).
| Funders | Funder number |
|---|---|
| U.S. Dept. of Energy | |
| U.S. Department of Energy | DE-AC05-00OR22725 |
| Battelle |
Keywords
- Doppler-free
- Low-density
- Quasi-static
- Stark broadening