FIGURE OF MERIT TO QUANTIFY THE SENSITIVITY OF MATERIALS TO RUNAWAY ELECTRONS IN A FUSION-REACTOR

After a brief discussion on the runaway electron problem in a fusion reactor, a new figure of merit, called the Runaway Electron Proof (REP) factor, is proposed. It assembles the stopping power of a material with respect to high energy electrons and its capability of withstanding high energy density deposition without damage. This figure is computed for the main candidate materials of the plasma facing components and its impact on the design is discussed.