Drift velocity of electron swarm in configuration space

In 1977, Tagashira and colleagues reported that the center-of-mass drift velocity W-r of an electron swarm defined in time of flight (TOF) takes a larger value than the drift velocity W-v defined in pulsed Townsend (PT) when ionization collisions take place. At the same time, they explained that the larger values of Wr are caused by the ionization generation of electrons at the front side of extending swarm clue to higher mean energy. In this paper, a new definition of virtual drift velocity in configuration space W'(r) defined in PT is proposed, and calculated data of drift velocities and related quantities such as ionization coefficients and ionization frequencies in Ar in a high E/N range are discussed relative to Tagashira's data. (c) 2006 Wiley Periodicals, Inc.