Evolution of an electron beam with azimuthal density nonuniformity in a cylindrical beam tunnel

We present the results on the deformation of the cross section of an electron beam in a cylindrical beam tunnel with ∂/∂z=0 and homogeneous magnetic field, due to azimuthally nonuniform current density distribution. For this purpose, a new three-dimensional, self-consistent, trajectory code has been used. In addition, a simple theoretical model has been seen to be adequate for the qualitative and quantitative interpretation of the numerical results. It has been found, that the azimuthal nonuniformity causes effects clearly associated with&oarr;E×&oarr;B drifts, but in absolute terms these effects are too small to affect the performance of a gyrotron.