Commissioning and Modeling of the High-Resolution X-Ray Imaging Spectrometer for Tungsten Transport Measurements on the W7-X Stellarator

We present progress and plans for core tungsten impurity transport studies on the Wendelstein 7-X (W7-X) stellarator utilizing X-ray measurements from the High-Resolution X-Ray Imaging Spectrometer (HR-XIS). Tungsten transport into the plasma core can dramatically affect plasma performance and the neoclassically optimized W7-X provides important regimes of study for this topic. The HR-XIS and X-Ray Imaging Crystal Spectroscopy (XICS) diagnostics are used to investigate impurity transport in the W7-X plasma by measuring emission from high-ionization states of injected impurities that are introduced to the plasma using the Laser Blow-Off (LBO) or TESPEL systems. These X-ray diagnostics have a 2 cm spatial and 5 ms temporal resolution and view selected wavelength regions over a 1 – 7.5 Å range with milli-angstrom resolution. Modeling of the system's full range of motion has increased the utilizable wavelength range of the HR-XIS diagnostic by a factor of 4. During the OP2.1 W7-X science campaign, this new capability was used to identify several previously inaccessible W emission lines originating from highly charged states between W43⁺ and W47⁺. Plans for the upcoming campaign regarding the implementation of impurity emission measurements to study core tungsten transport are discussed.