Measurements of the electron drift velocity and positive-ion mobility for gases containing CF 4

Abstract

Measurements of the electron drift velocity and positive-ion mobility for gases containing CF 4 have been performed. The results are presented for four types of gas mixtures containing CF 4 and hydrocarbons: CF 4+CH 4, CF 4+C 2H 6, CF 4+C 3H 8 and CF 4+iso-C 4H 10. To make a comparison, also positive-ion mobilities for Ar+C 2H 6 and Ar+C 3H 8 gas mixtures have been measured. The drift velocities of electrons in a few mixtures are found to exceed 10 cm/μs, twice that in a conventional drift chamber gas such as Ar(50%)+C 2H 6(50%). In particular, the electron drift velocity in CF 4(10%)+CH 4(90%) is larger than 10 cm/μs, even at a reduced electric field E/ P of more than 1 V/(cm Torr). Results on the measurements of the positive ion mobility are consistent with the interpretation that the hydrocarbon ions are the positive ions eventually drifting toward the cathode in the studied gas mixtures. Their mobilities in CF 4 are found to be smaller than those in Ar.