High-density electron gun with magnetic field

The paper describes an electron gun suitable for the production of a high-density beam of small diameter in high-power klystrons of very wide band. The beam is produced by a convergent gun, the cathode being merged in a properly shaped magnetic field produced by a partial shield. Both electric and magnetic fields have been calculated with great accuracy, allowing the experimental results to follow closely the theoretical ones. The practical realization is nevertheless easy, and no critical adjustment is necessary. There is no magnetic lens, and the focusing is obtained by a homogeneous magnetic field. A transmission of 99% was obtained with full modulation of the klystron.