Multiple Impurity Monitoring System For The HSX Stellarator

Diagnosing unexpected impurity contamination events as well as monitoring the densities of the expected ion, neutral and molecular species is critical to operating plasma confinement devices and can be achieved using wide-spectrum spectroscopy. The design, calibration and initial measurements from a lens based Czerny-Turner spectrometer developed to monitor impurity emissions at the HSX stellarator is presented. The system monitors a 40 nm wide spectrum with a spectra resolution of 0.1 nm and can be tuned to observe any region of the visible spectrum. In particular the wavelength range between 450 to 490 nm allows one to not only monitor the two primary fueling gases used in HSX, helium and hydrogen, but also to investigate line emissions signatures of contaminants including nitrogen, carbon and molecular contributions. This spectrometer is able to operate at a significantly higher frame rate (200 Hz) and signal level when compared to typical off the shelf broad band spectrometers due to its higher photon acceptance, and the low noise sCMOS Andor SONA camera used for light detection.