Brief introduction of Townsend discharge

Different working conditions cause different behavior of gas discharge with different discharge properties. In general, discharge is classified into two different kinds, one is non-self-sustained discharge, that is occurred at the existence of an extenal kmization source; the other is self-sustained, which can be maintained without the existence of the external ionization source. The conversion form the non-sustained to the sustained discharge is called the breakdown process of the gas. The investigation of this phenomenon and the set up of the Theory for the conversion were carried out by Townsend at the beginning of last century, thus it is called Townsend Discharge Theory.