Development of UV Spectroscopy for Improved Measurements of Tungsten Erosion & Re-deposition

A new high-resolution and high-throughput instrument is being developed to resolve the most promising W I lines observed in the range between 200 to 400 nm during ELMing and ELM free periods. Recently completed spectral surveys in the DIII-D and CTH experiments have identified numerous W I emission lines in the UV region which can be combined with atomic predictions to determine the erosion of plasma facing W surfaces. The importance of metastable level populations on the W spectrum requires that multiple W I emission lines be monitored simultaneously to accurately characterize erosion rates. These design criteria specify a wavelength resolution of 0.2 Å over a window of at least 12 nm with better than 20 ms resolution for measurements using vertically oriented slight lines into the DIII-D divertor. The design of a fiber coupled system located close to the DIII-D device for minimum UV signal attenuation is presented along with expected signal levels for DIII-D plasma conditions.