Princeton has developed an electromagnetic particle injector (EPI) which is a type of railgun that fires a high-velocity projectile from a pair of electrified rails into a plasma on the verge of disruption. The projectile, called a "sabot," releases a payload of material into the center of the plasma that radiates, or spreads out, the energy stored in the plasma, reducing its impact on the interior of the tokamak.
Current systems release pressurized gas or gas-propelled shattered pellets using a gas valve into the plasma, but with velocity limited by the mass of the gas particles.
The risk of disruptions is particularly great for ITER, the large international tokamak under construction in France to demonstrate the feasibility of fusion power. ITER's dense, high-power discharges of plasma, the state of matter that fuels fusion reactions, will make it difficult for current gas-propelled methods of mitigation to penetrate deeply enough into the highly energetic ITER plasma to take good effect.