The Existence of Non-unique Steady State Solutions to the RMF Current Drive Equations

Abstract

It is shown that the value of the d.c. current driven in a plasma cylinder by means of a rotating magnetic field (RMF) is not unique for R/o ;;:; 6 and eB",/vel m ~ R/o, where R is the radius of the plasma cylinder, a is the classical skin depth, Vel is the electron-ion momentum transfer collision frequency, B", is the magnitude of the rotating magnetic field, e is the electron charge and m is the electron mass. This effect is predicted using three distinct approaches: (i) a steady state analysis which ignores the second and higher harmonics of the fields and currents; (ii) a qualitative model which utilizes the analogy between the RMF current drive technique and the operation of the induction motor; (iii) a solution of the initial boundary value equations describing the RMF current drive in cylindrical plasmas.