The X-band coaxial cavity multi beam klystron(MBK) with its beam-wave interaction system and new type of pole controlled electron gun is studied.With the numerical simulation and experiment

the characteristic parameters of high mode TM

310

are achieved with the appropriate impedance and stable field distribution.Using the pole controlled electron gun with double focus electrodes and its optical system

the MBK can work both in pulse and continuous pattern

and the optimized geometry parameters with high quality hollow electron beam are obtained.The non-linear calculation of beam-wave interaction is used for the X-band MBK with six electron beams and five cavities.The results show that the output peak power is about 100 kW within 30MHz bandwidth

with the interaction efficiency more than

30%

and the gain above 36dB.