Development of Burst-mode Laser based High-speed Microwave and Thomson Scattering Instruments for Fusion Plasma Devices

Fusion plasma devices at various DOE and international facilities need high-speed diagnostic tools to understand, predict, and control fusion plasmas. Thomson scattering (TS) at tens of Hz has routinely measured electron temperature (Te) and electron number density (ne) inside the plasma system. However, at these data rates traditional TS can obtain only a sparse data set, which significantly limits in catching the plasma dynamics. Improved diagnostics with high temporal resolution are highly desired, as outlined at the 2015 Fusion Energy Science Workshop on Plasma Material Interactions and Workshop on Transients. Spectral Energies proposes to develop and commercialize hundreds-of-kHz-rate microwave and tens-of-kHz-rate Thomson scattering instruments based on diode and flashlamp-pumped burst-mode laser systems. Burst-mode lasers could be designed and operate in high-speed (up to MHz rates) or high-power (up to 2 Joule/pulse). Two key commercial products will be developed: 1) High-speed microwave scattering system for key atomic species (H & D) and electron number density and 2) High-speed Thomson scattering system for electron number density and electron temperature. The new improved diagnostics high-repetition-rates will enable unprecedented diagnostic capabilities and understanding for plasma instabilities, plasma wall interactions, and edge plasma characterizations and control. In Phase I, major research efforts will focus on demonstration of in-situ quantitative microwave and Thomson scattering from thermal plasma systems by optimizing the laser for pulse energy along with duration, shape, spacing, and wavelength to suppress the background scattering and stray light. The proposed techniques will be applied (possibly in Phase II) in the Prototype Material Plasma Exposure eXperiment (Proto-MPEX) at Oak Ridge National Laboratory (ORNL) or possibly at the Lithium Tokamak eXperiement Beta (LTX-Beta) device at Princeton Plasma Physics Laboratory (PPPL)