The Princeton Beta Experiment-Modification's advanced tokamak program

Recent experimental results in the fusion community have pointed to possible directions for improvement of the tokamak concept. A critical issue for many advanced tokamak scenarios is the optimization of the spatial distribution of plasma current density. Recent experiments on the Tokamak Fusion Test Reactor and Doublet III-D have demonstrated enhanced confinement and improved stability using transient techniques for the modification of the plasma current profile. The Princeton Beta Experiment-Modification (PBX-M) has begun experiments using profile modification techniques that are extrapolable to long-pulse or steady-state operation. PBX-M uses lower hybrid current drive for current profile modification, ion Bernstein wave heating for pressure profile variation, and plasma shaping to alter the magnetic geometry. This paper is an overview of the PBX-M program, its engineering facilities, and discussion of how this program is relevant to future advanced tokamak programs such as the Tokamak Physics Experiment.