Bulletin of the American Physical Society
56th Annual Meeting of the APS Division of Plasma Physics
Volume 59, Number 15
Monday–Friday, October 27–31, 2014; New Orleans, Louisiana
Session BP8: Poster Session I: MHD, Energetic Particles, Predictive Modeling, Plasma Surface Interactions; Diagnostic Measurements & Analysis; Non-Neutral, Anti-Matter & Strongly Coupled Plasmas; Plasma Technology
Monday, October 27, 2014
Room: Preservation Hall
Abstract ID: BAPS.2014.DPP.BP8.76
Abstract: BP8.00076 : Two Photon Absorption Laser Induced Fluorescence of Helium Ions in a Microwave Assisted Helicon Source*
Preview Abstract Abstract
(West Virginia University)
The spectroscopic measurement of helium ion velocity distribution functions in a low temperature plasma is problematic for a number of reasons. First and foremost is the difficulty in accessing the UV and soft x-ray transitions to the ground state. Conventional laser induced fluorescence on ions in plasmas is routinely performed in argon, neon, xenon, and barium. Two-photon absorption laser induced fluorescence (TALIF) on neutrals has been demonstrated in hydrogen, nitrogen, and oxygen plasmas. We have successfully performed LIF on helium atoms and have had some hints of success with laser absorption spectroscopy on excited states of helium ions, the n $=$ 5 to n $=$ 6 transition in the infrared (1012 nm). Here we report a new approach using TALIF to access the n $=$ 2 to n $=$ 6 transition of singly ionized helium. The fluorescence path at 656 nm completes the three-level sequence. To obtain the electron temperatures necessary to create a sufficient population of metastable helium ions trapped in the 2S state, we have increased the electron temperature of a helicon plasma with 1.2 kW of microwaves at 2.45 GHz. Here we report emission spectroscopy measurements that confirm the increase in excited state population densities and preliminary TALIF measurements on helium ions.
*This work is funded by the US Department of Energy through grant DE-SC0004736.
To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2014.DPP.BP8.76
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