Trail—A Tokamak Rail Gun Limiter

An attractive new limiter concept is investigated. The Tokamak RAIl Gun Limiter (TRAIL) system directs a stream of moderate velocity pellets (100 to 200 m/s) through the plasma edge region to absorb energy and define the plasma boundary. The pellets are recycled, after cooling, to the injector in an electromagnetic mass accelerator. Heat fluxes of ∼30000 W/cm² can be readily accommodated by the pellets, with very low recirculating power requirements (∼0.1%) for the accelerator. The mass accelerator velocity requirements are well within the present state of the art (several kilometres per second). Accelerators injecting pellets at ∼1 km/s can be used to control local plasma temperature and current profiles and to act as energy absorbers to shut down the plasma without damage to the first wall if a plasma disruption occurs.