SPARC Long Wavelength Diagnostics Overview*

SPARC is a compact, high-field, D-T tokamak that is presently under construction and will be used to de-risk ARC, the high-field path to commercial fusion energy. Diagnostic systems are entering the final design stage and will be used for real-time control and to close science gaps needed to design ARC. Long Wavelength diagnostics on SPARC tokamak consist of Interferometry, core Thomson Scattering, Electron Cyclotron Emission, Edge Scanning Reflectometry, UV, visible and IR Imaging and UV and visible Spectroscopy systems. Diagnostics employ unique features in design, calibration and measurement techniques, driven by SPARC's radiation environment, high magnetic fields, high densities and high temperatures. The engineering challenges for systems include space constraints and high thermal and electromagnetic loads, long transmission lines from the port towards the laboratory (approximately 20 m), and the necessity for radiation protection of signal processing equipment. Diagnostics share midplane port plugs and laboratory spaces, emphasizing the need for efficient integration and utilization of finite space near the plasma and through the penetration wall. Given limited in-vessel access due to activation, developing in-situ diagnostic calibration techniques is crucial for success and to plan for diagnostics on ARC.