Oblique electron-beam injection into plasma: effect of external magnetic field upon gun environment

When injecting an electron beam with a significant pitch-angle in a magnetoplasma, one has to take care that the parallel velocity of the electrons measured in the plasma does not only depend on the acceleration potential between the anode and the cathode of the electron gun, but also on the amplitude of the ambient magnetic field. The latter can play an important role when the actual acceleration distance of electrons in the gun vicinity, determined partly by collective processes that lead to potential modification in the gun environment, is large enough. Consequently, the actual beam pitch-angle can be noticeably different from the orientation of the electron gun.