Conceptual design of DIII-D experiments to diagnose the lifetime of spin polarized fuel

The D-T and D-³He fusion cross sections are increased by 50% if the fuel remains spin polarized parallel to the magnetic field, offering significant increase in fusion energy Q. The goal here is to assess the feasibility of spin polarization lifetime measurements on the DIII-D tokamak using relative changes in detected charged fusion product pitch, poloidal and energy distributions that depend upon the differential fusion cross section. Two realistic TRANSP calculated plasma scenarios are prepared: 1) Thermonuclear—utilizes polarized ³He and D pellet injection into a hot plasma, 2) Beam-plasma—uses polarized D pellets and unpolarized ³He neutral beams into an L-mode plasma. In both scenarios, there is pitch sensitivity for 15-MeV proton detection at a poloidal angle of -56^o, and sensitivity for 3.6-MeV alpha flux detection by an array of poloidal detectors. Energy-resolved measurements of protons in the beam-plasma scenario also show sensitivity at -56^o. A realistic assessment in the thermonuclear case show count rates ~10⁴ and 10⁵ cps for pitch-resolved proton and alpha flux measurements, respectively. Reduced chi-squared calculations show polarization lifetime measurements are feasible for proton or alpha detection.