Pellet injectors developed at PELIN for JET, TAE and HL-2A

Abstract Three innovative repetitive and multi-barrel deuterium ice pellet injectors have been designed for plasma investigations in fusion facilities. The pellet injector for JET can inject small pellets (variable volumes within 1-2 mm 3 ) at frequency up to 67 Hz and velocity 80–200 m/s for ELM (edge localised modes) control and large pellets (volume within 35–70 mm 3 ) at frequency up to 15 Hz and velocity 100–300 m/s for plasma fueling. A new extrusion nozzle has been designed and tested to improve the extrusion stability and injection reliability. The pellet injector for HL-2A has a piston type extruder with a variable cross-section. It allows pushing out deuterium ice rod from the extruder at velocity up to 100 mm/s and injecting a limited number of pellets 1.3 mm diameter and variable length in the range 1.3–1.7 mm at frequency up to 30 Hz for plasma fueling. The pellet injector for fueling of a facility with theta pinch plasma is capable to inject one pellet with variable length from 5 to 15 mm and diameter 1 mm with extremely low velocity of about 40–50 m/s, followed by eleven pellets with variable length from 1 to 3 mm and diameter 0.9 mm at velocities 100–200 m/s. A novel gas valve with in-built punch mechanism has been developed to simplify the injector design. The design and distinct features of these three injectors are presented.