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We present a compact improved model of the magnetically insulated line oscillator with new-type beam dump and other novel features. In the experiments, high-power microwave of the TM01 mode is generated from the device with a frequency range of 1.73–1.78 GHz and a peak power level of above 2 GW, when the diode voltage is taken in the range 520–540 kV, and the diode current is in the range 58–62 kA. This confirms the simulation results.

We propose a new method to increase the output power of a three-cavity transit-time oscillator (TC-TTO). Conventional transit-time effect oscillators, such as the split-cavity oscillator (SCO), super-Reltron, and TC-TTO (or double-foil SCO), etc., have a common feature that the span of any modulating cavity is uniform. The new method is to vary the three-cavity spans from uniform to nonuniform. Its configuration is called the nonuniform three-cavity transit-time oscillator (NTC-TTO). Numerical simulations show that the electron-beam is modulated more deeply in certain NTC-TTOs than that in the TC-TTO with the same whole modulating length, and the output microwave power in certain NTC-TTOs is higher than that in the TC-TTO. The experimental results are in agreement with those of the numerical simulations. The results show that the new method can increase the output power of a microwave tube based on the TC-TTO.

With a resonant cavity inserted between the second slow-wave-structure section and the tapered waveguide, a new structure of the multiwave Cerenkov generator (MWCG) operating at low guiding magnetic field is proposed to produce high efficiency and high power microwave. Some features and potential advantages of the proposed device are analysed. The 2.5-dimensional particle-in-cell simulation is employed to verify the initial expectation. The results show that, with the use of an electron beam of 640 keV and 8.4 kA guided by the magnetic field of 0.6 T, a stable and monochromatic X-band microwave output of 4 GW in peak power is achieved, and the average efficiency is over 30%.

A new configuration of an axially-extracted vircator with three resonant cavities is put forward and optimized by simulation with the PIC code. The output power of over 1 GW is obtained at around 4.1 GHz in the experiment, in agreement well with the PIC simulation results. The beam to wave power conversion efficiency is more than 6.6%.

The experimental results of an overmoded slow-wave high-power microwave generator operated at low magnetic field are presented. The feasibility of low magnetic field operation is investigated both theoretically and experimentally based on the characteristics of the overmoded slow-wave device. The experiments were carried out at the Spark-2 accelerator. Under the condition of guiding magnetic field strength of 0.55 T, diode voltage of 474 kV, and beam current of 5.2 kA, a microwave was generated with power of 510 MW, mode of TM01, and frequency of 9.54 GHz. The relative half-width of the frequency spectrum is less than 1%, and the beam-to-microwave efficiency is about 21% in our experiments.

We propose a new low-impedance high power microwave source based on the axial transit time effect, i.e. a low-impedance axial transit-time oscillator. The analysis and simulation are carried out to investigate the characteristics of this new configuration. In the numerical simulation, the microwave output peak power of 6 GW is obtained with an electron beam in the electron energy 580 keV and in the beam current 20 kA. The diode impedance is 29 Ω. The power of the input electron beam is 11.6 GW. The beam-to-microwave power conversion efficiency is 51.7%. The frequency is 3.9 GHz by numerical simulation.

The calculation and experimental study of two-cascade explosive-driven magnetic-field compression (EMC) pulsed power supplies is carried out. It is shown that: (1) under certain conditions, few-cascade EMCs can multiply current and electromagnetic energy; (2) with the worse figure of merit (P=0.54), it is possible to only multiply current, but not electromagnetic energy; (3) the "short and thick" devices have greater current and electromagnetic energy gain coefficient than "long and thin" ones-one of the important reasons is because of the better figure of merit; and (4) experimental data are consistent with calculation results.