In order to analyze the breakdown discharge characteristics of air gap at micrometer scale, a microgap discharge experimental platform was built to study the change of breakdown characteristics of air gap with the air pressure and electrode spacing in the range of electrode spacing between 1-100 μm. When the air pressure or electrode spacing was adjusted to make the breakdown voltage reach the lowest point, it was found that the breakdown voltage curve appeared a plateau, and corresponding to different external conditions, the length range of plateau was different. Through the simulation of microscale electric field, it was found that the electric field at the edge of electrodes was still in a higher range, within the range the self-sustaining discharge can still achieve. The collisional ionization process can reach breakdown between the electrodes through a longer path rather than the shortest distance, so that the breakdown voltage maintained at the lowest point, thus the plateau period was formed. When the electrode spacing was less than 10 μm, the ion-enhanced field emission mechanism was involved in the breakdown, and the lowest point of breakdown voltage continued to decrease from the plateau period. The number density of cathode ions was not only sensitive to the electrode spacing, but also influenced by the external air pressure, and the generated ion-enhanced field would enhance the intensity of field emission and further reduce the breakdown voltage. Combined with the analysis of air pressure and electrode spacing, the traditional Paschen’s law is no longer applicable in the micro-scale range, and the breakdown voltage is no longer determined by the product of the electrode distance d and the pressure p.
| 科 Family | 属数 Number of genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) | 属 Genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) |
|---|---|---|---|---|---|---|
| 鹅膏菌科Amanitaceae | 2 | 11 | 5.26 | 鹅膏菌属 Amanita | 10 | 4.78 |
| 小菇科 Mycenaceae | 2 | 12 | 5.74 | 丝盖伞属 Inocybe | 5 | 2.39 |
| 多孔菌科 Polyporaceae | 8 | 14 | 6.70 | 蜡蘑属 Laccaria | 5 | 2.39 |
| 红菇科 Russulaceae | 3 | 23 | 11.00 | 小皮伞属 Marasmius | 6 | 2.87 |
| 小菇属 Mycena | 11 | 5.26 | ||||
| 光柄菇属 Pluteus | 5 | 2.39 | ||||
| 红菇属 Russula | 17 | 8.13 | ||||
| 栓菌属 Trametes | 5 | 2.39 |