  The radiation response and the MHD destabilization during the thermal quench
after a mixed species Shattered Pellet Injection (SPI) with impurity species
neon and argon are investigated via 3D non-linear MHD simulation using the
JOREK code. Both the $n=0$ global current profile contraction and the local
helical cooling at each rational surface caused by the pellet fragments are
found to be responsible for MHD destabilization after the injection.
Significant current driven mode growth is observed as the fragments cross low
order rational surfaces, resulting in rapidly inward propagating stochastic
magnetic field, ultimately causing the core temperature collapse. The Thermal
Quench (TQ) is triggered as the fragments arrive on the $q=1$ or $q=2$ surface
depending on the exact $q$ profile and thus mode structure. When injecting from
a single toroidal location, strong radiation asymmetry is found before and
during the TQ as a result of the unrelaxed impurity density profile along the
field line and asymmetric outward heat flux. Such asymmetry gradually relaxes
over the course of the TQ, and is entirely eliminated by the end of it.
Simulation results indicate that the aforementioned asymmetric radiation
behavior could be significantly mitigated by injection from toroidally opposite
locations, provided that the time delay between the two injectors is shorter
than $1ms$. It is also found that the MHD response are sensitive to the
relative timing and injection configuration in these multiple injection cases.
