High-power multibeam klystron with reversive magnetic focusing system

The development of superhigh power multibeam klystrons for linear accelerators is of interest because of the reduction of operational voltage, improvement of the form of the anode pulse and increase of the efficiency. Thus the longitudinal dimensions of the klystrons are essentially reduced (as compared with one-beam klystrons), the HF field strengths in the gaps of the cavities are decreased and a number of the constructive and technological solutions becomes simpler. The problem of the increase of the cathode current density, which is known for multibeam klystrons, can be eliminated by transition to the resonant systems operating at the higher modes. It allows us to increase the sizes of the cathodes and to place them axially symmetrically on rather large diameters. Due to such a technical solution, the cathode current density of the multibeam klystron can be reduced to the values, which are characteristic for single-beam klystrons. The authors consider the development of a 7-cavity 18-beam relativistic klystron with an output power of 75 MW and compare it with the known parameters of the single-beam 50 MW, 11.4 GHz klystron applicable to SLAC.