Drift Velocities of Low Energy Electrons in Argon at 293 and 90 K

Abstract

The drift velocity of electrons in argon has been measured at 90 K in the range 0�002 ,;;; E/ N (Td) :.;; 0�7 and at 293 K in the range 0�01 ,;;; E/N (Td) ,;;; 1�0. The high sensitivity of the drift velocities to the presence of small quantities of diatomic impurities, particularly nitrogen, was demonstrated by adding known but trace quantities of diatomic gases. In this way it was observed that the presence of 6 p.p.m. nitrogen in the argon gave errors in the drift velocity of up to 3 %. As a result it was necessary to purify research grade gas before use. A full discussion is given of the errors incurred in the measurements.