Negative DC Corona Discharges in Supercritical Carbon Dioxide

摘要

In our previous work, positive dc discharge plasmas have been measured and analyzed. In present studies, the measurements for breakdown voltages were made with point-plane electrodes for high-pressure carbon dioxide (CO_2) up to supercritical conditions under negative DC applied voltage. Negative dc corona (glow discharge) is Trichel pulses. Corona pulses, whether positive or negative, are streamers: each pulse is a streamer. The results exhibit a dramatic phenomenon: corona discharge can be generated, and corona discharge area is formed from onset to spark breakdown with a very low voltage at critical point and in its close vicinity, where no corona discharge exists in normal high pressure gas. An explanation is probably because of the unique characteristic anomaly of large fluctuations in the density and energy at critical point and in its close vicinity, where the extensive unstable clusters are formed, and the mean free path of electrons are increased.