The Electromagnetic Particle Injector as a Fast Time Response Disruption Mitigation System

Predicting and controlling disruptions is an important and urgent issue for ITER. Some disruptions with a short warning time may be unavoidable. For these cases, a fast time response disruption mitigation method is essential. A novel rapid time-response disruption mitigation system (DMS), referred to as the Electromagnetic Particle Injector (EPI), is being developed for tokamak-based reactors and as a backup option for ITER. Experimental tests on a prototype system have been able to verify the primary advantages of the concept. These are its ability to meet short warning time scales of <10 ms while attaining the projected high velocities for deep radiative payload penetration in reactor-scale plasmas. The EPI relies on an electromagnetic propulsion system. A metallic sabot is accelerated electromagnetically to the required velocities (> 1 km/s) within 2 ms, at which point it releases a radiative payload consisting of a shell pellet or well-defined microspheres. Initial experimental tests from the prototype system show attainment of over 600 m/s in about 1 ms. Essential aspects of payload separation from the sabot and sabot capture have also been demonstrated at 200 m/s, and the method can be extended to over 2 km/s. Results from the operation of the EPI-2 system that uses 3 T boost magnetic fields and EPI design projections to ITER will be described [Raman et al., Nuclear Fusion 61 (2021) 126034].