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High-power microwave-induced low-pressure discharges seriously threaten the reliability of space payload systems. Under extremely low-pressure conditions, the evolution of ionized and secondary electrons at the initial stage of discharge is crucial to figure out the discharge process. Therefore, this paper investigates the development of multiple electrons in the discharge process under a highly low-pressure environment using numerical simulation. A three-dimensional simulation model based on the Monte Carlo algorithm is established by considering various electron-gas collisions and secondary electron emissions from different material surfaces. The evolution characteristics of various electrons' populations, energy, and distribution patterns during the discharge process are analyzed. In addition, the influence of the critical conditions at different air pressures on the electron evolution during the discharge process and the intrinsic causes are also investigated. This study is significant in revealing the transition characteristics between multipactor and low-pressure discharge and exploring their inherent mechanisms. [ABSTRACT FROM AUTHOR]

PTFE (Polytetrafluoroethylene) with a low dielectric constant and less microwave loss is widely applied in dielectric microstrip antenna and has a significant prospect on low-cost miniaturization satellite cluster. In contrast, the surface discharging induced by space electron beam irradiation degrade antenna radiation efficiency and generate pulse interference signal, which comes to be the critical challenge for employing in orbit. In this paper, we use an experiment and simulation combined method for avoiding surface discharging current path to figure out the charging states and gas desorption phenomenon. The charging state numerical simulation calculates secondary electron emission and deposited electron-hole pair distribution with the Monte Carlo simulation. In addition, we investigate the surface gas desorption, chemical state, as well as morphology of PTFE film under different irradiation situations in situ. We find that the electron irradiation with a higher energy can result in a more frequent discharging, meanwhile, coming with a lower surface discharging potential yet. In spite of a less incident current, the gas desorption rate under the satisfied discharging irradiation presents to be larger than the none discharging irradiation situation. Under the 20 keV E-beam irradiation, the F1s spectrum translates more remarkably, and the C1s spectrum presents a greater promotion on breakage of C–F bond. The presented results and numerical simulation method in this study can offer a comprehensive insight into researches and developments on dielectric microstrip antenna in space. [ABSTRACT FROM AUTHOR]

Methane is one of the most important gases leading to the earth's air pollution. Ventilation air methane(VAM) is an important part of the gas discharged into the atmosphere. The volume concentration of methane is generally less than 0.5% in coal mines. Recycling low concentration is facing challenges. To explore the law of low concentration methane enrichment, the enrichment tower for methane was designed and manufactured. The experiment was divided into two types - free diffusion and weak eddy enrichment, and eight kinds of low concentration gas experimental program. Under free diffusion conditions, the maximum methane concentration of the top (middle) tower is 0.64% (0.53%). In the condition of weak eddy field, the maximum methane concentration is 0.67% (0.69%) in the top (middle) tower. The effect of methane enrichment in the weak eddy field is obvious. Methane enrichment method under the eddy current field can greatly increase methane enrichment efficiency and achieve the goal of CMM (coal mine methane) power generation. [ABSTRACT FROM AUTHOR]