Runaway electrons in SPARC*

We explore the evolution and diagnosis of post-disruption runaway electrons (REs) in the SPARC V0 tokamak design [1]. The RE problem may be worsened by high plasma currents ($I_p\sim$~7.5~MA) better confining REs, and compact size ($R_0\sim$~1.65~m, $a\sim$~0.5 m) leading to faster current quench times. However, the high magnetic field ($B_0\sim$~12~T) will increase synchrotron power loss, $>5\times$ higher than ITER. The code GO [2] is used to model the electric field and RE current profiles during realistic SPARC disruption scenarios. Scans are performed in post-disruption plasma temperature, thermal quench time, and pre-disruption elongation. The kinetic equation solver CODE [3] is used to evolve the RE momentum space distribution function, giving expected energies of the RE plateau. Recent findings from \emph{quiescent} RE experiments in Alcator C-Mod indicate that the spectra, polarization, and images of RE synchrotron radiation can give insight into RE energy, pitch angle, and spatial distributions, respectively [4-6].\newline [1] Greenwald 2018 PSFC/RR-18-2 [2] Smith 2006 PoP 13 [3] Landreman 2014 CPC 185 [4] Tinguely 2018 NF 58 [5] Tinguely 2019 NF accepted [6] Tinguely 2018 PPCF 60