Runaway Electron Mitigation Coil Self Activating Switch

In advanced fusion machines, high current beams (megamps) of relativistic electrons (10s of MeV) can cause severe damage to plasma-facing surfaces of a tokamak structure (Runaway Electrons, or RE). This catastrophic destruction includes melt damage, coolant leaks, loss of vacuum, and if it occurs once in every 1000 shots could prevent fusion machines from reaching commercial viability. Fusion-produced electric power is a carbon-free energy source with a nearly inexhaustible fuel source (deuterium) and with few of the potential hazards of conventional nuclear fission. Unlike many of the present renewable sources (solar and wind) it is available 24/7 on demand and can be sited nearly anywhere. Reliable and economical electric power is crucial to U.S. economic growth and necessary for a high quality of life. It is in the public’s interest for DOE to investigate a scientific solution applicable across the fusion industry. All fusion machines can benefit from an effective and timely resolution to this critical problem. This proposal addresses the development of a vacuum feedthrough and fast-acting, high current switch controlling a magnetic coil which eliminates destructive electron beams from fusion machines. The problem will be addressed by theoretical design, numerical analyses, and hardware construction. The full-scale switch and feedthrough will be installed in a working fusion device for full-scale tests. Future installation of a prototype is planned on a fusion device. In Phase I, design of the switch and feedthrough and tested critical components of the final system occurred. Analytical designs, numerical modeling and critical component hardware fabrication were performed to establish feasibility. Objectives: Update the specification with the lessons learned from the critical components testing; design, fabricate, and test the 350-kA switch and feedthrough inhouse and on a fusion device; and finalize a design for a 350-kA class switch and radiation resistant feedthrough for other fusion pilot plants. Other tokamaks that could use the switch and feedthrough will be identified and discussion will occur with the appropriate technical points of contact to see if any differences to the specifications arise. The fusion industry is growing rapidly focused on high current, high magnetic field machines. These machines are the target market.