| Autor: |
Chakraborty Thakur, Saikat, McCarren, Dustin, Carr, Jerry, Scime, Earl E. |
| Předmět: |
|
| Zdroj: |
Review of Scientific Instruments; Feb2012, Vol. 83 Issue 2, p023508, 8p, 3 Diagrams, 4 Graphs |
| Abstrakt: |
We report continuous wave cavity ring down spectroscopy (CW-CRDS) measurements of ion velocity distribution functions (VDFs) in low pressure argon helicon plasma (magnetic field strength of 600 G, Te ≈ 4 eV and n ≈ 5 × 1011 cm-3). Laser induced fluorescence (LIF) is routinely used to measure VDFs of argon ions, argon neutrals, helium neutrals, and xenon ions in helicon sources. Here, we describe a CW-CRDS diagnostic based on a narrow line width, tunable diode laser as an alternative technique to measure VDFs in similar regimes but where LIF is inapplicable. Being an ultra-sensitive, cavity enhanced absorption spectroscopic technique; CW-CRDS can also provide a direct quantitative measurement of the absolute metastable state density. The proof of principle CW-CRDS measurements presented here are of the Doppler broadened absorption spectrum of Ar II at 668.6138 nm. Extrapolating from these initial measurements, it is expected that this diagnostic is suitable for neutrals and ions in plasmas ranging in density from 1 × 109 cm-3 to 1 × 1013 cm-3 and target species temperatures less than 20 eV. [ABSTRACT FROM AUTHOR] |
| Databáze: |
Complementary Index |
| Externí odkaz: |
|
