LoWEUS, the Long Wavelength Extreme Ultraviolet Spectrometer, on the NSTX tokamak*

LoWEUS is a high-resolution ($\lambda / \delta\lambda = \sim 200 $) grazing-incidence grating spectrometer from the LLNL electron beam ion trap program that was installed on the NSTX tokamak in the spring of 2008 to monitor emission lines in the long wavelength extreme ultraviolet band. As currently set up, LoWEUS covers the 55-225 {\AA} region, which includes important emission lines of oxygen and iron, among others. Most importantly, it observes the emission from hydrogenlike and heliumlike lithium (Li$^{2+}$ and Li$^+$, respectively). LoWEUS is thus complementary to the XEUS (also from LLNL) and SPRED spectrometers. The initial operation of LoWEUS, which was cut short by a valve issue, enabled us to perform a survey of emission lines of intrinsic impurities in NSTX.