Fast ion driven instabilities, transport, and diagnostic opportunities in SPARC*

In the highest performing plasma discharge, the SPARC tokamak expects to produce ~28 MW of DT-fusion alpha particles [Creely 2020 JPP], born with energies 3.5 MeV and velocities ~13e6 m/s. Moreover, more than 10 MW of Ion Cyclotron Resonant Heating, using a Helium-3 (or Hydrogen) minority population, will accelerate these ions to energies of order 1 MeV. Even with a high on-axis magnetic field strength of 12.2 T, SPARC's Alfven speed is ~9e6 m/s, meaning that fast ions can destabilize MHD instabilities such as Alfven Eigenmodes (AEs) and other energetic particle modes. This poster will explore the existence and stability of AEs with linear codes NOVA-K [Gorelenkov 1999 PoP] and FAR3D [Varela 2017 NF], as well as nonlinear MEGA [Todo 1998 PoP] simulations. Resulting fast ion transport will be investigated with guiding-center ORBIT [Podesta 2017 PPCF] and gyro-orbit ASCOT [Varje 2019] simulations, with effects on plasma performance evaluated with TRANSP [Breslau 2018]. Opportunities for diagnosing confined and lost fast ions as well as related MHD will also be presented, for example by high frequency magnetics, gamma spectroscopy, interferometry, and imaging.