Research On The Output Section Of High Power Broadband Multi-Beam Klystron

The dissertation expounds a series of in-depth researches on the output section of high power broadband multi-beam klystron and the main fruits.The first, the effect of the sizes of coupling slots in a coupling double gap cavity on the cavity characteristics is studied through simulation computation of three dimensions electromagnetic field and analysis of equivalent lumped element circuit. It is concluded by the research that, in lower frequency band, bigger coupling slots in a coupling double gap cavity are beneficial to raising the characteristic impedance and lowering the frequency of it mode. So a new kind of microwave cavity- π mode strongly coupling double gap cavity, which has higher characteristic impedance, smaller volume and fits in with lower frequency band multi-beam klystrons, is proposed.The second, a complete simulation computation method for output circuit of broadband klystron is developed, basing on existing program ISFEL3D for simulation computation of three dimensions electromagnetic field, principle of output circuit of broadband klystron and microwave network theory. Some practical examples are calculated and the calculated results are compared with cold test results, so that the reliability of the simulation computation method is proven.The third, some groping researches are made on broadband coaxial line filter output circuit of klystron. A broadband output circuit-π mode four coupling slots double-gap output cavity loaded with coaxial filter, which has a workable relative bandwidth bigger than 14% and fits in with L-band multi-beam klystron, is designed. Meanwhile some analysis of its stability and peak power capacity is made.The fourth, the power capacity and the special harmfulness of ghost mode resonance when a cylindrical box type window is used to transmit high power CW are studied in detail. The existing formula for calculating the average transmitting power capacity of cylindrical TE11 mode box type window is revised and a formula for three dimensions simulation computation of the temperature increment of the dielectric disk in cylindrical TE11 mode box type window is deduced. Meanwhile a valuable conclusion that general cylindrical box type windows with dielectric disks made of Al2O3 ceramic can be used to transmit CW of higher power than 120kW and workable relative bandwidth may achieve about 14% in L band, is made by calculated results of some typical examples.