  A spectral survey of tungsten emission in the ultraviolet region has been
completed in the DIII-D tokamak and the CTH torsatron to assess the potential
benefit of UV emission for the diagnosis of gross W erosion. A total of 29 W I
spectral lines are observed from the two experiments using survey spectrometers
between 200-400 nm with level identifications provided based on a structure
calculation for many of the excited states that produce strong emission lines.
Of the 29 observed lines, 20 have not previously been reported in fusion
relevant plasmas, including an intense line at 265.65 nm which could be
important for benchmarking the frequently exploited line at 400.88 nm. Nearly
all of the observed spectral lines decay down to one of the six lowest energy
levels for neutral W, which are likely to be long-lived metastable states. The
impact of metastable level populations on the W I emission spectrum and any
erosion measurement utilizing a spectroscopic technique is potentially
significant. Nevertheless, the high density of W I emission in the UV region
allows for the possibly of determining the relative metastable fractions and
plasma parameters local to the erosion region. Additionally, the lines observed
in this work could be used to perform multiple independent gross erosion
measurements, leading to more accurate diagnosis of gross tungsten erosion.
