Deceleration mechanism of spheromak-like compact toroid penetrating into magnetized plasmas

Abstract

To understand the fueling process in a fusion device by a spheromak-like compact toroid (SCT) injection method, magnetohydrodynamic numerical simulations, where a SCT is injected into magnetized target plasmas, have been carried out so far. As a result, it has been found that the SCT penetration into magnetized target plasmas is accompanied by complex physical dynamics, which is not adequately described by the conventional simple theoretical model. In this study, based on the previous simulation results, a new theoretical model to determine the penetration depth of the SCT is represented. Here, the SCT is considered to be decelerated not only by the magnetic pressure force but also by the magnetic tension force, which is generated by the bending of the target magnetic field as a result of the SCT penetration. Furthermore, by comparing the penetration depth of the SCT estimated from the theoretical model with that in the simulation, the accuracy of the model is examined. Finally, the effect of magnetic reconnection on the SCT penetration is discussed.