D.A. Nesterov - Student, Department "Electronic devices and equipment", Saratov State Technical University named after Gagarin Yu.A. E-mail: enlucioro@gmail.com
V.A. Tsarev - Dr.Sc. (Eng.), Professor, Department "Electronic devices and equipment", Saratov State Technical University named after Gagarin Yu.A. E mail:tsarev_va@mail.ru

Increasing the number of beams in multibeam devices results in a decrease of accelerating voltage and increase spread of the effective characteristic impedances values in drift tubes on different ring layers. One solution to this problem is development a step non-uniform cavities, which thickness of the central bushing increases with distance from the cavity center. In the ordinary slot double - gap cavity / the product of interaction square gap coupling and characteristic impedance, associating with bandwidth and gain of the device, decreases significantly with increasing distance from the cavity center. Furthermore, there is a greater non-uniformity of the RF field along the radius, resulting in reduces efficiency of the electronic efficiency of the device. The step non-uniform design modification of the slot double-gap cavity allows achieving more uniform interaction multibeam electron with the UHF field. Calculations showed that the spread of the effective characteristic impedances values along the radius in a new design is 9.5% for the antiphase mode (instead of 23% at the same gaps). At the second harmonic frequency, corresponding to an inphase mode, the spreading does not exceed 15% (instead of 35%). This allows increasing gain-bandwidth value of the device.