The effect of Shattered Pellet Injection (SPI) with full impurity pellets on the radiative energy loss and MHD modes is studied by the reduced MHD model of the JOREK code with a JET target equilibrium and injection configurations resembling that of the JET SPI system. Comparing with the deuterium SPI case, the n=0 current profile contraction is found to play a more important role due to the more efficient cooling, while the destabilizing helical effect still persists. Strong and broad-spectrum MHD perturbations emerge as the cooling front approaches the q=2 surface, resulting in widespread field line stochasticity, and the consequential n=0 current profile relaxation. Strong toroidal asymmetry of the radiation profile is identified, as well as a poloidal asymmetry which changes over time as pellet fragments travel through flux surfaces. It is found that impurity radiation is able to deplete more than 80% of the pre-injection thermal energy even for the smallest JET SPI caliber quantity. Furthermore, the impact of injection parameters is demonstrated and the effect of SPI for different target q profiles and temperature profiles will also be discussed in order to provide insight for the development of the future ITER disruption mitigation system.
Study of full impurity Shattered Pellet Injection by non-linear 3D JOREK simulation in JET plasma
Bonfiglio D;
2018
Abstract
The effect of Shattered Pellet Injection (SPI) with full impurity pellets on the radiative energy loss and MHD modes is studied by the reduced MHD model of the JOREK code with a JET target equilibrium and injection configurations resembling that of the JET SPI system. Comparing with the deuterium SPI case, the n=0 current profile contraction is found to play a more important role due to the more efficient cooling, while the destabilizing helical effect still persists. Strong and broad-spectrum MHD perturbations emerge as the cooling front approaches the q=2 surface, resulting in widespread field line stochasticity, and the consequential n=0 current profile relaxation. Strong toroidal asymmetry of the radiation profile is identified, as well as a poloidal asymmetry which changes over time as pellet fragments travel through flux surfaces. It is found that impurity radiation is able to deplete more than 80% of the pre-injection thermal energy even for the smallest JET SPI caliber quantity. Furthermore, the impact of injection parameters is demonstrated and the effect of SPI for different target q profiles and temperature profiles will also be discussed in order to provide insight for the development of the future ITER disruption mitigation system.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
