A team of experts at Oak Ridge National Laboratory (ORNL) is taking aim at one of the biggest challenges facing ITER: turning cold gas into wine-cork-sized, solid pellets to help keep the plasma in check.
A shattered pellet injector is a device that pre-empts plasma disruptions by releasing a spray of frozen deuterium-neon pellets into a plasma. The frozen pellet fragments, injected at speeds up to 250 metres per second, rapidly decrease the plasma temperature, thereby dissipating energy and minimizing potential damage to plasma-facing surfaces during a disruption. Photo: ORNL
The ORNL team also needed to rethink how to shoot the pellet into the tokamak. In other tokamaks, a valve based on a magnetic circuit opens to release high-pressure gas at the pellet—but magnetic circuits will not work in ITER's high magnetic fields. So Gebhart improved a special flyer plate valve that does function in those fields.
Gebhart prepares the high-speed camera he uses to photograph pellets inside a pellet injection system he uses for R&D. The team at ORNL is helping to adapt shattered pellet injection technology to ITER-sized pellets, which are about the size of wine corks. Photo: ORNL