Figure 1
From: Radio-frequency current drive for thermonuclear fusion reactors

Scheme of axisymmetric toroidal column of plasma, magnetically trapped in a tokamak machine by static magnetic field, BT, produced by a solenoid surrounding the column. R and r are, respectively, the major and minor radial coordinates, R0 indicates the position of the column axis, and a is the last closed magnetic surface (LCMS).