Selectable flight tube design developments for iter fueling, ELM pacing, and impurity pellets

ITER fueling and Edge Localized Mode (ELM) pacing pellets will be created by punching and chambering pellets with a solenoid operated cutter from an extrudate formed by a twin-screw extruder. The cut pellets are then accelerated down a flight tube by a fast pneumatic valve. The impurity pellets are formed in-situ with a pipe gun technique and accelerated down a flight tube with the same pneumatic valve design. The pellets are directed into three possible plasma locations by the flight tube selector. The pellets exit the selector and travel through flight tubes that penetrate the cryostat and vacuum vessel before entering the plasma on either the outer diameter (low field side) or inner diameter (high field side). The geometries of the flight tubes have been optimized to maximize bend radii over 800 mm to ensure intact pellets traveling at >200 m/s. A proof of concept selector was built and tested to verify pellet survivability through the selector inlet and output tubes as well as the two internal selector funnels. The ENEA/ORNL highspeed pellet injection system was adapted for selector testing to provide both 4.4 mm and 3.2 mm diameter deuterium pellets as fueling and ELM pacing pellet surrogates respectfully. The pellets were accelerated with a limited quantity of propellant gas of ~13 mbar-L to mimic the expected ITER pellet speeds. The pipe gun barrel had to be kept near 16 K to lower the pellet shear strength to enable the pellets to release from the barrel when fired.