A second fuelling system, a pellet injector, will also be used at ITER. The pellet injector is mainly a highly-efficient ice maker. An extruder punches out several millimeter-sized deuterium-tritium ice pellets that are propelled by a gas gun up to 3,600 km/h—fast and cold enough to penetrate deep into the plasma core. The frozen pellets are injected through a guide tube located in the inner wall of the vacuum vessel and another guide tube for outer wall injection.
The ''closed DT loop'' fuelling cycle of ITER. Stored deuterium and tritium are introduced into the vacuum chamber where only a small percentage of the fuel is consumed. The plasma exhaust is removed and processed through an isotope separation system that extracts out the fusion fuels for reinjection into the fuelling cycle.