First Results of Thermal Helium Beam and Impurity Spectroscopy at the DIII-D Helicon Antenna

A thermal helium beam diagnostic (He-Beam) has been commissioned at the DIII-D tokamak. The diagnostic aims to measure the radial profiles of plasma density, temperature, and impurities in the DIII-D scrape-off layer surrounding the helicon antenna. These measurements are vital for evaluating plasma heating methods and the general characterization of the DIII-D boundary plasma. The diagnostic is composed of two spectrometers with eighteen lines of sight each. One spectrometer measures the emission lines of thermal helium, and using a collisional radiative model (CRM), the radial density and temperature profiles can be inferred. The second spectrometer is used for impurity spectroscopy. This contribution presents the details of the implementation and first analysis of three plasma discharges as examples. The data was acquired with 10 ms temporal resolution to be comparable with helicon antenna modulation. Changes in the line emission intensity of up to two orders of magnitude were detected between scenarios with and without the helicon antenna power injection. Preliminary results indicated minor changes in impurities associated with helicon antenna operation and, after system calibration, allow plasma parameter estimation based on a dedicated helium CRM. The first results for these scenarios will be presented and discussed.