Resistive Wall Mode Internal Structure Identification by Soft X-Ray Contrast Enhancing Technique

79101S In fusion systems, the effectiveness of direct feedback control of resistive wall mode (RWM) depends critically on the real-time identification of and accurate diagnostic information on early low-amplitude mode structure. The internal structure of RWM cannot be extracted solely from external magnetic measurements and requires diagnostics able to measure inside the plasma column. This project will develop and test an improved soft x-ray ¿contrast enhancing¿ technique (SXR CET) for the internal structure identification of RWM. The SXR CET will be implemented and validated as a part of an integrated system for direct feedback control of RWM. We demonstrated the SXR CET proof-of-principle and presented its improved signal-to-noise, contrast enhancing, and capability of low-amplitude mode detection in a recently published paper. During Phase I, the SXR CET will be designed with an improved setup on DIII-D, and its detection capability for very slowly growing RWM will be tested. The ability to discriminate between rotating and non-rotating plasmas to measure error field resonant amplification will be determined. Commercial Applications and Other Benefits as described by the awardee: The SXR CET should be a key component for the optimal control of fusion plasma reactors. The final product, an integrated diagnostic tool, should be suitable and adaptable for other plasma processing installations.