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Two photon absorption laser induced fluorescence measurements of neutral density in a helicon plasmaa )
| Content Provider | Semantic Scholar |
|---|---|
| Author | Galante, Matthew E. Magee, Rachel M. Scime, Earl E. |
| Copyright Year | 2014 |
| Abstract | We have developed a new diagnostic based on two-photon absorption laser induced fluorescence (TALIF). We use a high intensity (5 MW/cm), narrow bandwidth (0.1 cm ) laser to probe the ground state of neutral hydrogen, deuterium and krypton with spatial resolution better than 0.2 cm, a time resolution of 10 ns, and a measurement cadence of 20 Hz. Here, we describe proof-of-principle measurements in a helicon plasma source that demonstrate the TALIF diagnostic is capable of measuring neutral densities spanning four orders of magnitude; comparable to the edge neutral gradients predicted in the DIII-D tokamak pedestal. The measurements are performed in hydrogen and deuterium plasmas and absolute calibration is accomplished through TALIF measurements in neutral krypton. The optical configuration employed is confocal, i.e., both light injection and collection are accomplished with a single lens through a single optical port in the vacuum vessel. The wavelength resolution of the diagnostic is sufficient to separate hydrogen and deuterium spectra and we present measurements from mixed hydrogen and deuterium plasmas that demonstrate isotopic abundance measurements are feasible. Time resolved measurements also allow us to explore the evolution of the neutral hydrogen density and temperature and effects of wall recycling. We find that the atomic neutral density grows rapidly at the initiation of the discharge, reaching the steady-state value within 1 ms. Additionally, we find that neutral hydrogen atoms are born with 0.08 eV temperatures, not 2 eV as is typically assumed. VC 2014 AIP Publishing LLC. [http://dx.doi.org/10.1063/1.4873900] |
| File Format | PDF HTM / HTML |
| Alternate Webpage(s) | https://ulysses.phys.wvu.edu/plasma/pdf/PoP_2014_Galante.pdf |
| Language | English |
| Access Restriction | Open |
| Subject Keyword | Adaptive Internet Protocol Assumed Blood Vessel Tissue Calibration Deuterium Discharger File spanning Fluorescence Gradient Ground state Helicon Filter Hydrogen Ionolyce helicon Krypton Lunar Lander Challenge Microwave Photons Plasma Active Recycling Steady state density orders - HL7PublishingDomain wavelength |
| Content Type | Text |
| Resource Type | Article |
