Radiation asymmetry and MHD destabilization during the thermal quench after impurity Shattered Pellet Injection

Abstract

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.

arXiv comment35 pages, 21 figures

References in corpus (5)

• Ionization Equilibrium Timescales in Collisional Plasmas
• Test particles dynamics in the JOREK 3D non-linear MHD code and application to electron transport in a disruption simulation
• Fast plasma dilution in ITER with pure Deuterium Shattered Pellet Injection
• First predictive simulations for deuterium shattered pellet injection in ASDEX Upgrade
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Cited by in corpus (14)

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• Plasmoid drift and first wall heat deposition during ITER H-mode dual-SPIs in JOREK simulations
• Bayesian optimization of massive material injection for disruption mitigation in tokamaks
• Radiated energy fraction of SPI-induced disruptions at ASDEX Upgrade
• Fluid and kinetic studies of tokamak disruptions using Bayesian optimization
• Runaway dynamics in reactor-scale spherical tokamak disruptions
• Non-linear MHD modelling of shattered pellet injection in ASDEX Upgrade
• Magnetic island formation and rotation braking induced by low-Z impurity penetration in an EAST plasma
• Reduced kinetic modelling of shattered pellet injection in ASDEX Upgrade
• Hot-tail electrons' impact on assimilation and injection penetration of D2 Shattered Pellet Injections
• First numerical analysis of runaway electron generation in tungsten-rich plasmas towards ITER
• Collisional-radiative non-equilibrium impurity treatment for JOREK simulations
• Stability impacts from the current and pressure profile modifications within finite sized island