April 13, 2017
Plasma disruptions are fast events in tokamak plasmas that lead to the complete loss of the thermal and magnetic energy stored in the plasma. The plasma control system in ITER will be responsible for minimizing the number of these events—especially when running high energy deuterium-tritium plasmas—but the probability of disruption will never be zero.
But designing an effective and reliable disruption mitigation system for ITER is not only a technological challenge, it also requires a good understanding of the physics mechanisms driving disruptions to allow scientists to predict that a certain design will be effective. This is why a workshop was jointly organized by ITER's Plant Engineering and Science & Operations departments to bring physics experts together with the US ITER engineers based at Oak Ridge National Laboratory (ORNL) developing the design of the disruption mitigation system. About 25 leading experts from the Members' fusion research centers and universities joined the intensive discussions during the three-day workshop from 7 to 9 March 2017.
The workshop participants were asked to put ITER-specific engineering constraints aside to have a fresh look at possible concepts for the disruption mitigation system. From the discussion it became clear that the most promising approach at present is to inject the material through shattered pellet injection, which is also the present baseline concept. This technique freezes deuterium, neon, or argon gas to form cryogenic pellets as large as a wine cork. These pellets are accelerated to velocities of up to 500 m/s and broken into shards by a sharp bend at the end of the flight tube. This is intended to ensure that a high fraction of the injected material is assimilated by the plasma.
Source: ITER Newsline
Last Updated: January 16, 2019 - 2:36 pm