Systematic study of the electrical characteristics of the ``Trichel'' current pulses from negative needle-to-plane coronas

When a negative dc voltage is applied to a needle in an electronegative gas such as atmospheric air, highly regular corona current pulses (Trichel pulses) are observed under some conditions. Systematic variation of the macroscopic experimental parameters has yielded the functional dependence of the pulse frequency, charge per pulse, and time-averaged corona current on the applied voltage, needle-tip radius, and needle-to-plane spacing. In combination with a theoretical analysis of the motion of the charge clouds, these results yield new insight into the physical mechanism of this gas-discharge phenomenon. For example, above threshold voltage, it appears that several negative-ion-charge clouds are simultaneously in transit across the gap.