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The heat transfer processes associated with the heating of the operating liquid and the calibration of the liquid calorimeters for measuring the energy of high-power microwave pulses are studied analytically and by numerical simulation. It is shown that convection significantly enhances heat transfer between the calibration and thermostabilization heaters and the operating liquid, hence, it helps to reduce the formation of bubbles in the volume of the operating liquid when controlling and calibrating the calorimeter. Heat transfer from tape heaters is noticeably more efficient than that from single wire ones. The results obtained are essential for the development of liquid calorimeters and the adjustment of their operating modes.

The paper describes a study of a new relativistic microwave Cherenkov generator of millimeter wavelength range with the transverse dimension of the electrodynamic system D>2.5λ, where D is the average diameter of the slow wave structure, and λ is the radiation wavelength. The investigations were carried out with a high-current SINUS-200 electron accelerator at a voltage of 473 kV and an electron beam current of 3.8 kA. The use of several, complementing each other, mechanisms of suppression of parasitic waves provides stable microwave generation at a specified frequency of 36.4 GHz. The microwave power in the experiment 804 MW with 45% beam-to microwave power conversion.

The mode convertor design of fundamental coaxial TEM to the lowest asymmetric TE11-mode of a circular waveguide was proposed and optimized with ANSYS HFSS software. It includes axially aligned parts: the input coaxial line with the high voltage insulator, conical coaxial matching line, wave-coax transition section and output circular waveguide. The most losses in this type of convertor caused by the wave of coaxial TE11-mode running back to the microwave source. To minimize these losses, there is the matching conical coaxial line with the cut-off insertion for coaxial TE11-mode. Characteristics of the convertor are as follows: the maximum input peak power – 3GW, the input impedance – 28Ohm, the central operating frequency – 1.14GHz. The power conversion efficiency to the output mode is from 90% upto 100% in the frequency band of 20%.

An electron beam with a virtual cathode (VC) transported in a two-section drift tube of a SINUS-7 high-current electron accelerator has been studied. The dependence of the VC velocity on the injected current has been experimentally determined for the first time. It is established that the VC motion in the drift tube is accompanied by microwave oscillations, which are caused by transient processes involved in the formation of a compressed electron beam.

This paper studies the motion of a virtual cathode in a two-section drift tube with the formation and breakup of the “compressed” state of an electron beam. Experimental arrangements to intercept part of the injected current during the voltage pulse and to provide virtual cathode motion toward the collector are proposed. The arrangements were implemented on the SINUS-7 high-current electron accelerator. Theoretical and experimental dependences of the virtual cathode velocity on the injected current and cathode voltage are presented. The experimental data on virtual cathode motion agree with its theoretical model based on analytical solutions of equations assisted by computer simulation with the PIC code KARAT. The results of the work demonstrate the feasibility of controlling the virtual cathode motion which can be used in collective ion acceleration and microwave generation.