The results of an experimental and a numerical study of a relativistic A6 magnetron with single radial microwave power output slot operating with angular segment (AS) NdFeB permanent magnets placed inside the anode vanes and cylindrical rod magnets inside the cathode are presented. With permanent magnets, ~10−7 s long pulses of tens of megawatts of microwave power with an electronic efficiency of ~7% are generated. The results of experiments and simulations show that electron losses near the poles of the anode magnets where magnetic field lines cross the anode-cathode gap limit the microwave generation efficiency.

We present main results of recent experimental studies of relativistic S-band 6-cavity magnetron powered by a Linear Induction Accelerator (350 kV, 2.5 kA, 150 ns). It is shown that the shift in the magnetron cavity resonance frequency into the range of the frequencies obtained during the magnetron operation is affected by the magnetron output design leading to efficient $(\eta\geq 40\%)$ microwave generation during~ 1 00 ns of the microwave pulse. 1 Using a proper stabilization of the frequency of the microwaves (250 MW, ~ 1 00 ns) generated by the magnetron, the latter was used pump a compressor based on a travelling wave resonator producing at its output microwave pulses with a power of $1. 15\pm 0.05$ ; GW and duration of $12\pm 2$ ns.2 In addition, it was demonstrated that the distribution of the microwave power between the three outputs allows wedge insulators to be used in the waveguides vacuum-air interface without electrical breakdown. Microwave radiation, extracted in free space by three horn antennas, was coherently added to each other resulting the power flux density at desired location of ~55kW/cm 2 , which would require a microwave source radiating in free space through one antenna ~ 1. 7GW. 3 Finally, it will be shown that the field intensity in cavities adjacent to the extraction cavity differs by ~3 times and that the field intensity gradually increases along the series of cavities and the direction of this increase coincides with the direction of the electrons' ExB drift. 4

The results of an experimental study of the S-band magnetron operation with a six-vane anode block and multichannel radial outputs for microwave power extraction are presented. The magnetron was driven by a linear induction accelerator (similar to 350 kV, similar to 2.5 kA, and 150 ns). In the case of three outputs for microwave power extraction and another three outputs connected to waveguides short circuited by movable plungers for adjusting the magnetron resonance, frequency-stable generation of the microwaves radiation with a total power of 570 MW from these three outputs was demonstrated. This power was equal to the power obtained when the same magnetron with one output was operated with high efficiency (>= 40%). In addition, it was shown that the distribution of the generated microwave power between the three outputs allows wedge insulators to be used in the waveguides vacuum-air interface without electrical breakdown. Finally, microwave radiation, extracted in free space by a cluster of horn antennas connected at the output of the waveguides, was coherently added to each other at the desired distance with a three times larger microwave power density than in the case of 570-MW single output magnetron operation.

Plasma evolution in the interference switch of an S-band pulse compressor operating in the frequency of 2.766 GHz, with input pulses of 200-450-kW power and duration of 2.4 μs, was studied experimentally and in numerical simulations. The system was filled with dry air at 2 × 10 5 -3 × 10 5 -Pa pressure. The plasma discharge that switches the phases of the compressor operation from energy storage to release was initiated by a Surelite laser. The evolution of the light emission from the plasma was studied using fast-framing optical imaging with a 4QuikE camera. From the obtained typical size of the plasma and its velocity of expansion along the electric field, the density of the plasma was estimated, and the influence of its evolution on the power and waveform of microwave output pulses observed in the experiments was determined in simulations.

The results of experiments on the reproducible generation of an electron beam having a high current density of up to 300 A/cm2 and a satisfactorily uniform cross-sectional distribution of current density in a ∼200 kV, ∼450 ns vacuum diode with a carbon-epoxy capillary cathode are presented. It was found that the source of the electrons is the plasma formed as a result of flashover inside the capillaries. It is shown that the plasma formation occurs at an electric field ≤15 kV/cm and that the cathode sustains thousands of pulses without degradation in its emission properties. Time- and space-resolved visible light observation and spectroscopy analyses were used to determine the cathode plasma’s density, temperature, and expansion velocity. It was found that the density of the cathode plasma decreases rapidly in relation to the distance from the cathode. In addition, it was found that the main reason for the short-circuiting of the accelerating gap is the formation and expansion of the anode plasma. Finally, it was shown that when an external guiding magnetic field is present, the injection of the electron beam into the drift space with a current amplitude exceeding its critical value changes the radial distribution of the current density of the electron beam because the inner electrons are reflected from the virtual cathode.