Survey Spectroscopy in the Large Plasma Device

Survey spectroscopy is used on the Large Plasma Device (LAPD) to determine plasma impurities like carbon, as well as plasma parameters, namely electron temperature and density. We used an OceanInsight survey spectrometer to collect spectral data over a range of operating conditions. To visualize this spectral data, a graphical user interface that produces live updates is created in conjunction with a server to communicate between the spectrometer and the LAPD control room. A new LaB₆ plasma source with a graphite heater has been installed on LAPD — unsurprisingly carbon emission is observed in the data. The ability to track carbon impurities is a valuable diagnostic on the plasma and the health of the plasma source and graphite heater. We have compared observed spectral data from several species with predictions using the ColRadPy¹ collisional-radiative solver. The comparison between the observed and ColRadPy-produced spectra provides a method to confirm electron temperature and density measurements, and may allow independent measurements of these quantities using line-ratio information from the experimental data. Results from these comparisons will be presented and prospects for survey spectroscopy as a diagnostic tool for LAPD will be discussed.

1. C.A. Johnson, S.D. Loch, D.A. Ennis, Nuclear Materials and Energy, August 2019, 20 100579