The JET high frequency pellet injector project

A new deuterium ice pellet injector is in preparation for JET. It is designed to inject both small pellets (variable volume within 1–2 mm 3) at high frequency (up to 60 Hz) for ELM mitigation experiments and large pellets (volume within 35–70 mm 3) at moderate frequency (up to 15 Hz) for plasma fuelling. It is based on the screw extruder technology developed by PELIN and pneumatic acceleration. An injection line will connect the injector to the flight tubes already in place to convey the pellets toward the plasma either from the low field side or from the high field side of the torus. This injection line enables: (i) the pumping of the propellant gas, (ii) the provision of the vacuum interface with the torus and (iii) the selection of the flight tube to be used via a fast selector. All the interfaces have been designed and a prototype injector is being built, to demonstrate that the required performance is achievable.