Status and Plans for the Ionizing Radiation Diagnostics on SPARC

The SPARC tokamak plans to begin operations in mid-2026 and execute a series of mission-driven campaigns to demonstrate net energy, Q_fus > 1, and to close tokamak science gaps required to complete the design of ARC. Information from passive emission of neutrons and photons over the X-ray and vacuum ultraviolet (VUV) spectral range will be used for real-time control and to support physics studies. This contribution provides a summary of planned neutron, X-ray and VUV measurements as well as their present status of design and construction. Neutron diagnostics included flux monitors, foil activation monitors, a 19-ch poloidally viewing imaging camera and a single chord, midplane viewing magnetic recoil proton spectrometer. Present plans for calibration of fusion power measurements are described. X-ray diagnostics include in-vessel diamond-based pinhole cameras and ex-vessel scintillator-based hard x-ray sensors. A set of 5 beamlines view X-rays from the core with each having a PHA and low-resolution crystal spectrometer for impurity monitoring and two high-resolution crystal spectrometers for ion temperature and toroidal rotation. A single chord VUV spectrometer views the core over 1-20 nm and the upper and lower inner and outer divertor are monitored over 20-200 nm. Not all capabilities will be fully deployed in Campaign #1 and plans for stepwise increase in capability, including opportunities for collaboration via private-public partnerships, are outlined.