A W-band extended interaction oscillator (EIO) driven by a pseudospark-sourced sheet electron beam (PS-SEB) is demonstrated in this letter. The idea of combining the advantages of a pseudospark-sourced electron beam (high beam current density), a sheet electron beam geometry (large beam cross-sectional area) and a ladder-like slow wave structure (high gain per unit length) to generate powerful millimeter-wave radiation was experimentally verified. The PS-SEB based EIO produced ~1.2 kW peak output power, an increase of six times in the measured power from an EIO based on a pseudospark-sourced pencil electron beam. Such a methodology offers a promising solution for portable, low-cost and powerful millimeter-wave and terahertz-wave radiation sources.

Conductive particles are one of the most important defects which can greatly degrade the performance of gas-insulated metal-enclosed switchgear (GIS). Many efforts have been made to clarify the influence on the withstand voltage, understand the flashover mechanism, and build a comprehensive model to describe the particle-initiated flashover. In this study, a partial discharge (PD) signal detected through a photomultiplier (PMT) and recorded by a high-speed data acquisition (DAQ) system was used to analyze the discharge development of a conductive particle-contaminated GIS insulator under constant high AC voltage. An additional PMT was used as a reference to eliminate the dark count of the PMT and the data collection method of a DAQ system was optimized to capture the pulse waveform of each PD to obtain detailed physical information. Spectra of the PD pulse amplitude over pulse width, PD counts within various amplitude ranges over time and phase resolved partial discharge (PRPD) patterns of the PDs in different stages are obtained through the captured PD waveforms. Characteristics of the PDs from the application of the high AC voltage up to the flashover of the insulator were then analyzed, and it was found that the features of the PDs in the near-flashover stage were significantly different to the previous stages.

The experimental study of a pseudospark discharge sourced electron beam with post acceleration (PA) is presented. The PA circuit was used to drive a W-band extended interaction oscillator. The experiments showed a significant increase in the output power, with 200 W at 94 GHz measuring corresponding to a 5 times increase in the output power as compared to when post acceleration is not used. The microwave device developed has the advantage of not requiring an external magnetic field making it a low cost, compact, and portable sub-terahertz radiation source.

Electrical explosion of aluminum wire is a very promising method for aluminum nanoparticle production. The exploding wire plasma has significant influence on the formation of the nanoparticles. In this paper, the electron temperatures and the electron densities in the plasma are estimated through Boltzmann plot and Stark broadening effect. The aluminum particle densities, charge state distributions, and the energy relaxation in the plasma are estimated accordingly. The diffusion of the plasma into protective argon gas is studied through its spatial distribution. The electron temperatures of the electrical explosion of wire (EEW) plasma with an aluminum wire in argon gas are 1~2 eV, and the electron densities are of the order of magnitude ~1019/cm3, which decrease rapidly over time after the EEW occurs. The diffusion of the EEW plasma of aluminum wire into ambient argon gas can be divided into two main phases, namely, the previous fast diffusion phase and the subsequent slow diffusion phase. The plasma is with quite different diffusion features due to the differences of the corresponding relative number density of the plasma to argon gas. For plasma with relative density much higher than 1, the diffusion velocity in the fast diffusion phase is significantly higher than that with relative density near 1, and in the slow diffusion phase, the distribution radius of the plasma can continue to increase significantly due to the considerable energy coupled from the circuit to the aluminum particles. Dependence of the plasma radii on the deposited energies are derived from the experimental data. For plasma with relative density near 1, due to the much longer relaxation time during the slow diffusion phase, very little energy can be transferred from the circuit to the aluminum particles and the plasma radii only increase slightly during this phase after the aluminum particles spent most of their kinetic energy in the previous fast diffusion phase.

Diamond-like carbon (DLC)-modified alumina microparticles are expected to be an ideal filler that can greatly improve the thermal conductivity of epoxy-alumina composites with a high fill factor, while the composites can still maintain high dielectric properties. Plasma-enhanced chemical vapor deposition (PECVD) has been mostly used to prepare DLC film on bulk material, and the ion energy in the plasma shows a crucial influence on the properties of the DLC. However, the properties of the DLC on solid microparticles prepared through the PECVD method as well as the effect of the ion energy are still unclear. In this paper, DLC on alumina microparticles has been prepared through a highly efficient method of repeated pulsed hollow cathode discharge in methane gas, and the characteristics of the DLC on the alumina particles have been studied and analyzed. The morphology and bond composition of DLC on particles have been studied through electron microscopy, Raman spectrometer and x-ray photoelectron spectroscopy. The ion energy distribution in the discharge plasma was diagnosed and used to analyze its effect on the hybrid bond content of the DLC through correlation analysis. The correlation of the ion energies and the hybrid bond content of the DLC shows that hydrocarbon ions in the discharge plasma with an energy of 100–200 eV present the most benefit to the formation of the sp³ hybrid bond content of DLC film on alumina microparticles. In addition, hydrogen ions with an energy of 700–1000 eV are also beneficial to improve the sp³ hybrid bond content of the DLC film.

The ability to manipulate ion energy is crucial for the practical implementation of pulsed hollow cathode discharge in plasma deposition. This paper presents a method for generating plasma through double pulse voltage superposition, which excites the hollow cathode discharge. By superimposing a high-amplitude pulse with a narrow width and a low-amplitude pulse with an extended width, gas ionization and ion acceleration can be stimulated respectively. With this approach, relative independent control over ion flux density and ion energy becomes possible. Increasing the amplitude of the narrow pulse enhances the ion flux density, while increasing the amplitude of the long pulse boosts average ion energy.