New pellet injector from US lab powers fusion record breakthrough

Researchers at Oak Ridge National Laboratory (ORNL) have developed a novel high-speed pellet injector that significantly advanced fusion energy research by enabling a record-breaking plasma performance at the Wendelstein 7-X (W7-X) stellarator in Germany. This Continuous Pellet Fueling System injects a steady stream of solid hydrogen pellets, cooled near absolute zero and accelerated by helium gas, directly into the plasma core. This deep fueling method effectively raises the plasma’s core density more efficiently than traditional gas injection from the vessel’s edge, which is crucial for sustaining the plasma’s energy confinement and achieving the fusion “triple product” — the simultaneous attainment of high ion temperature, density, and energy confinement time. The W7-X stellarator, known for its complex three-dimensional magnetic confinement, had previously struggled to maintain high plasma density for extended periods, limiting sustained high-performance operation. The ORNL pellet injector overcame this limitation by maintaining a higher plasma density, which uniquely enhances energy confinement in stellarators. This breakthrough allowed