Focuser for electron beam and travelling-wave tube equipped with such a focuser

摘要

Focuser for electron beam, with relatively weak magnetic field and relatively long period. To facilitate the focusing of a beam, the focuser includes, in addition to the conventional large magnet 1-2, small magnets 10, 11, 12-20, 21, 22 arranged and oriented in such a way as to modify the periodic variation in the magnetic field along the axis Z'Z of the focuser in such a way that there is created a strong harmonic 3 and higher harmonic distortion, in phase opposition at the level of the maximum in the field of the fundamental. Application, in particular, to the focusing of beams produced by travelling-wave tubes operating at high frequencies and high power. IMAGE