Refuelling of plasma machines by pellet injection with a centrifuge

In refuelling plasma machines with large plasma diameter and high density and temperature the gas intake is likely to be insufficient. This applies particularly to plasma machines operated with divertor. Great importance is thus attached to refuelling by injection of frozen hydrogen pellets. It is also hoped that the plasma parameters can be influenced by pellet injection. Till now pneumatic pellet injectors and centrifuges have been used to attain pellet velocities above 200 m/s. This paper affords an insight into the present performance of pellet injection by centrifuge. Besides the rotor material and geometry, the shape of the accelerating channel and its significance in relation to the forced acceleration of pellets is also treated. The problem of preparing solid hydrogen and introducing it into the accelerating channel and the influence of this on the exit scatter of pellets are discussed. The peripheral equipment required for centrifugal acceleration, such as pellet diagnostics, pellet beam tube into the plasma, and control synchronization facilities, are briefly touched on. (orig.)