Non-axisymmetric Radiation Modeling of JET SPI Discharges Using Emis3D

Precise radiated power values in tokamak disruptions are required to ensure stored energy in net energy tokamaks like ITER and SPARC is well mitigated. In mitigated disruptions, 3D MHD modes and localized impurity sources break toroidal symmetry. To incorporate asymmetric radiation structures, the Emis3D code adopts a physics motivated guess-and-check approach. Virtual radiation structures are observed with the Cherab modeling framework [M. Carr EPS 2017] and a best fit chosen using a reduced χ² statistic. 2D axisymmetric inversions, helical structures, and 3D MHD simulated distributions from JOREK [Huysmans NF 2007] are tested. Two JET discharges terminated by shattered neon pellets are analyzed. 2D inversions are the best fit to the current quench, but helical structures are within uncertainty. Helicals fit the pre-thermal quench (pre-TQ) best and exhibit a parallel flow towards the high-field side. JOREK agreement to experiment in the pre-TQ is improved by increasing fidelity of the impurity source. Radiated fractions of 0.95 +0.05/-0.31 and 0.98 +0.02/-0.26 are found, suggesting that the stored energy may have been fully mitigated.