Influence of non-uniform magnetic field distribution on gyrotron spurious oscillations

The SELFT code has been modified to study the influence of B=B(z) on spurious oscillations. An initial attempt has been made to simulate the spurious oscillations in the cavity for an example (W7X 140GHz, TE
_{-28, 8}
mode gyrotron). The radio frequency (RF) spectrum at the end of the simulation (using B=B(z)) clearly indicates the presence of spurious oscillations.