50 Hz deuterium pellet injector for EAST tokamak

A new high frequency pellet injector has been developed for edge localized mode mitigation and plasma fuelling of the EAST tokamak. The pellet injector consists of two independent modules operating at 1-25 Hz. Both modules are equipped with screw extruders cooled by liquid helium for solid deuterium ice production at steady state mode. An innovative pellet fabrication and acceleration system has been designed and applied to reduce gas load on the extruders in 4-5 times and to increase the pellet injection reliability. Pellets of 1.5 mm diameter and 1.5 mm length were injected at 250 ± 50 m/s velocity at 25 Hz with reliability over 93% using one module in preliminary tests. Two modules working in turn are under tests now. It is anticipated they will be able to inject pellets at 50 Hz after further technical improvements in near future.