Bulletin of the American Physical Society
64th Annual Meeting of the APS Division of Plasma Physics
Volume 67, Number 15
Monday–Friday, October 17–21, 2022; Spokane, Washington
Session GP11: Poster Session III: In-Person, Hall A (9:30-11:00am) and Virtual Poster Presentations (11:15am-12:30pm)
MFE: DIII-D
Low Temperature Plasma
FUND: Dusty Plasmas; Plasma Sources
9:30 AM - 12:30 PM
Tuesday, October 18, 2022
Room: Exhibit Hall A and Online
Abstract: GP11.00124 : Preliminary Results from a Three Photon Laser Induced Fluorescence Diagnostic in a Cold Krypton Gas*
Presenter:
Thomas E Steinberger
(West Virginia University)
Authors:
Thomas E Steinberger
(West Virginia University)
Jacob McLaughlin
(University of Iowa)
Ripudaman S Nirwan
(West Virginia University)
Earl Scime
(West Virginia University)
Remotely situated, portable diagnostics are desired for fusion devices since electromagnetic interference (EMI) and radiation are becoming ever more intense. Specifically, diagnostics capable of measuring absolute neutral densities are critical to understanding fusion processes. Two-photon absorption laser induced fluorescence (TALIF) is one such technique that non-perturbatively measures spatially resolved neutral velocity distribution functions (NVDF) to determine absolute, ground state neutral density if the measurements are calibrated with a noble gas, commonly krypton or xenon. However, TALIF injects deep ultraviolet light (~205 nm) that is easily absorbed in air, restricting the location of the diagnostic system to regions of potentially high EMI and eliminates use of fibers and common optic materials. A three-photon laser induced fluorescence (3pLIF) technique probes the same states and species as interrogated using TALIF, while injecting a more near-visible wavelength, 300-308 nm, alleviating the restrictions for special optics, allowing the use of high-power fibers, and allows the laser system to be situated further from the intense EMI environment. In this work, a Quantel Qscan pulsed dye laser produces either ~300 nm (3pLIF) light or ~204 nm (TALIF) light over ~7 ns at a repetition of 10 Hz. Fluorescence is fiber coupled to detecting electronics. Here preliminary krypton NVDFs measured using 3pLIF are presented and compared to krypton NVDFs measured using TALIF. Integrated signals are measured across a variety of laser pulse energies to determine regions of laser saturation for each technique. A relative krypton multiphoton cross section between TALIF and 3pLIF is determined.
*This work was supported by Department of Energy Grant No. DE-SC0021406 and the West Virginia University Kinetic Center for Plasma Physics. The authors wish to thank The Naval Research Laboratory for key experimental apparatus components.
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