In fusion devices, hot plasma will be brought into contact with materials in the divertor regions to extract energy and waste helium produced in the fusion reaction. Under the harsh plasma conditions, from high particle and heat fluxes, these plasma facing components (PFCs) have severely short lifetimes. One method of reducing the power load and extend the lifetime of the PFCs is collisional and radiative cooling of the plasma through a volume of neutral gas above the material surface. Concerns over the machine integrity through material erosion, as well as fuel retention in PFCs necessitates a better understanding of the complex plasma-material interactions.
Neutral particles such as atomic hydrogen, as well as their temperature, play an important role in basic plasma processes, since their density and temperature can greatly influence the plasma dynamics and the plasma chemistry. Two-photon absorbed laser-induced fluorescence (TALIF) is one of the most sensitive methods of measuring atomic and molecular species in a plasma. It can provide excellent temporal and spatial resolution of densities, temperatures, surface loss probabilities, erosion and deposition precursors.
This mid-term presentation will discuss using nitrogen to radiatively cool plasma in the divertor of fusion devices and additional complexes that it introduces, such as ammonia formation, and the experimental studies currently underway investigating the plasma physics and chemistry in divertor relevant plasmas.