Theoretical investigations on radiation generation of TEM, linearly or circularly polarized TEn1 coaxial waveguide mode in relativistic magnetron

The physical mechanism of the radiation generation of all possible output modes of the relativistic magnetron (RM) with all cavity-magnetron axial extraction technique is theoretically analysed, and the necessary conditions for generating these modes are obtained respectively. Assuming that n 0 is the number of the electron spokes, N ≥ 4 as the total number of the cavities is an even number, and k is a nonnegative integer, some conclusions can be drawn as follows. If n 0 = kN is true, no mode can be excited in the coaxial waveguide; if n 0 = (2k + 1)N/4 is true, the linearly polarized modes can be excited in the coaxial waveguide; if n 0 = (4k + 2)N/4 is true, the TEM mode and the linearly polarized modes can be excited in the coaxial waveguide; if n 0 takes other value, the left and right circularly polarized modes can be excited in the coaxial waveguide and the directions of rotation of the circularly polarized modes can be reversed with the reversion of the direction of rotation of the electron spokes; in addition, some other regular characteristics of the corresponding mode excitation are presented in detail in this paper. Such unique attractive properties that have been verified by the cold and hot simulations in this paper make it possible for this type of RM to meet application requirements of various high power microwave (HPM) modes.