A High-Resolution Magnetic Proton Recoil Neutron Spectrometer for Burning Plasma Diagnosis in SPARC*

This poster presents the design of a high-resolution neutron spectrometer to be installed on the SPARC tokamak. SPARC will employ a suite of neutron diagnostics to accurately assess the fusion performance of the reactor. Within this suite, a Magnetic Proton Recoil (MPR) spectrometer [1][2] will provide unique insight into the kinetic physics of the fusion plasma, being capable of measuring core ion temperature, fuel concentrations, and fast particle populations. In addition, the highly collimated view of the plasma and collocation with the neutron camera enables an optical calibration strategy for interpreting flux measurements of the spectrometer, potentially giving an independent absolutely calibrated measure of the fusion rate and power gain factor, Q [3]. The MPR technique relies on 3 main components: a proton conversion and selection system, a set of magnets to focus and disperse the scattered protons, and a hodoscope in the focal plane on the ion optics. Uncertainty and efficiency of the proton conversion process is assessed using SRIM [4], and the ion optics have been optimized using COSY [5]. The system is designed for a variable energy acceptance in order to measure spectral features from 1-20MeV, with energy resolution dE/E<1% and a time resolution dt<200ms during high performance discharges.