Theory of high-frequency waves in a coaxial plasma wave guide

An analysis of the high-frequency eigenmodes of a coaxial wave guide contai ning a magnetized annular plasma column is presented. A transcendental equa tion is derived from the boundary conditions in the form of an eighth-order determinant equated to zero. Simultaneous solution of this determinantal e quation and a polynomial equation derived from the wave equation yields the dispersion relations for the eigenmodes. By reduction of the order of the determinant the appropriate transcendental equation is easily obtained for some special cases, e.g., partially filled coaxial wave guide. The electros tatic treatment of a coaxial cylindrical wave guide is also presented. The corresponding transcendental equation is reduced to some special cases, e.g ., conventional wave guide containing an annular plasma column under electr ostatic approximation. Numerical solutions are obtained for some azimuthall y symmetric EH (perturbed TM) and HE (perturbed TE) wave guide modes, cyclo tron modes, and space-charge modes. A strong dependence of the frequencies of these electromagnetic-electrostatic waves on the radii of the coaxial wa ve guide and the plasma column is revealed. (C) 1999 American Institute of Physics. [S1070-664X(99)03509-0].