Advances in singly connected closed field line plasma devices and extrapolation to POP level experiments and reactors

Abstract

Recent advances in creating stable, hot, steady-state field-reversed-configuration (FRC) plasmas using rotating magnetic fields (RMF) have made this an appropriate time for reexamining the old field-reversed-mirror (FRM) concept. The reactor advantages of such a linear, naturally high beta configuration would be enormous, but previous attempts to produce field reversal using tangential neutral beam injection (TNBI) alone were unsuccessful. Simple scalable extensions of present RMF produced FRCs can result in ideal traps for TNBI produced energetic ions, and detailed calculations show high efficiencies of TNBI production of energetic ion rings within such FRCs. If non-standard MHD effects such as strong flow and highly energetic ions are able to extend FRC stability to larger sizes, then the principal need will be to reduce present high values of anomalous cross-field resistivity. Experimental trends show how this may be achieved, and the present experimental and theoretical status of the most basic issues of FRC stability, confinement, and current drive are summarized, along with the new calculations on TNBI. The parameters for a modest sized 'proof-of-principle' device which can address these basic issues, as well as provide enough flux for efficient TNBI trapping, are given.