Effect of aperture in a pole piece for focusing of multi beam electron gun

Conventional microwave tubes generally use cylindrical electron beam coaxial to RF interaction circuit for generation or amplification of microwave signals. Many performance limitations these tubes in respect of band width, efficiency, voltage break have been addressed by emerging multi-beam technology which uses several low perveance electron beams in place of single beam used in conventional tubes. Design and development of a four beam electron gun is being attempted at CEERI with an aim to develop a multi-beam klystron. An approach has been developed to design four beam electron gun and focusing system. Effect of pole pieces for confinement of beam is studied and a proper pole piece size and shape is investigated using software OPERA 3D and OmniTrak simulation codes to enhance laminarity of beam. The paper presents the some of design results.