Assessment of a magnet system combining the advantages of cable-in conduit forced-flow and pool-boiling magnets

This paper presents an idea for a magnet system that could be used to advantage in tokamaks and other fusion engineering devices. Higher performance designs, specifically newer tokamaks such as those for the International Thermonuclear Engineering Reactor (ITER) and Tokamak Physics Experiment (TPX), use cable-in-conduit conductor (CICC) forced-flow coils to meet field and current-density requirements. Pool-boiling magnets have limited structural integrity because helium cooling areas must surround each conductor. CICC magnets eliminate these disadvantages by using internal cooling. However, the CICC system introduces other disadvantages, in particular, there may be leaks in the sheath at an inaccessible location. The system proposed here is basically a CICC system, with it's inherent advantages, but bathed in supercritical helium to eliminate the leak and voltage breakdown problems. Schemes to simplify helium-coolant plumbing with the proposed system are discussed. The advantages and disadvantages of using supercritical helium in combination with solid electrical insulation in a CICC system are discussed.