Progress on Multielement Spectroscopic Temperature and Impurity Studies on a High Flow Velocity Z-Pinch

Multiple spectroscopy diagnostics have been fielded on the FuZE-Q sheared-flow-stabilized (SFS) Z-pinch to measure plasma impurities, flow velocity, temperature, and density. The spectroscopy diagnostics currently cover the wavelengths from extreme ultraviolet (EUV) in the 5–40 nm (30–250 eV) range, ion Doppler spectroscopy (IDS) in the 225–233 nm range, to compact broadband spectroscopy (UV/VIS) in the 220–1050 nm range. Spectral databases and collisional-radiative (CR) modeling have been used to identify impurities and estimate plasma parameters. Many emission lines from deuterium (D), carbon (C), and oxygen (O) have been identified, at this time. Current line-emission spectroscopy is sensitive to relatively low temperatures characteristic of the edge plasma, outside the fusion core. Temperature estimates using O as an EUV spectroscopic tracer have been compared to IDS estimates using C. EUV and IDS spectra find evidence of an ensemble of edge plasma temperatures in device-commissioning shots. Modeling line pairs involving B-like, Be-like, Li-like, and He-like O yielded electron temperatures from 16 to 155 eV. This profile is comparable to ion temperatures observed by IDS from Doppler broadening of Be-like C (34 eV) and He-like C (298 eV). Deposition and debris from within FuZE-Q have been analyzed with scanning electron microscope (SEM) energy dispersive X-ray spectroscopy (EDS) and find evidence of C, O, Si, W, Al, Cu, Fe, and Cr. Synthetic spectra from CR modeling, informed by plasma numerical simulations, can be compared to experimental spectra and thereby benchmark the calculations. Measurements of the edge plasma provide insight into plasma-wall interactions. Impurity identification is vital for radiative power and scientific
$\emph{Q}$
calculations.