Abstract
Experiments are needed to test and extend present understanding of confinement, macroscopic stability, alpha-driven instabilities, and particle/power exhaust in plasmas dominated by alpha heating. A key issue is to what extent pressure profile evolution driven by strong alpha heating will act to self-organize advanced configurations with large bootstrap current fractions and internal transport barriers. A design study of a Fusion Ignition Research Experiment (FIRE) is underway to assess near term opportunities for advancing the scientific understanding of self-heated fusion plasmas. The emphasis is on understanding the behavior of fusion plasmas dominated by alpha heating (Q ≥ 5) that are sustained for durations comparable to the characteristic plasma time scales (≥ 20 τE and ~ τskin, where τskin is the time for the plasma current profile to redistribute at fixed current). The programmatic mission of FIRE is to attain, explore, understand and optimize alphadominated plasmas to provide knowledge for the design of attractive magnetic fusion energy systems. The programmatic strategy is to access the alpha-heating-dominated regime with confidence using the present advanced tokamak data base (e.g., Elmy-H-mode, ≤ 0.75 Greenwald density) while maintaining the flexibility for accessing and exploring other advanced tokamak modes (e. g., reversed shear, pellet enhanced performance) at lower magnetic fields and fusion power for longer durations in later stages of the experimental program. A major goal is to develop a design concept that could meet these physics objectives with a construction cost in the range of $1B.
