Observations of electron temperature relaxation rates in rare gas afterglow plasmas

The single Langmuir probe technique has been used to determine the relaxation rates of the electron temperature, T e , in repetitively produced, time-resolved afterglow plasmas. Comprehensive data is presented for krypton plasmas together with preliminary data for neon and argon plasmas. The electron temperature cooling curves for a given gas pressure, p 0 , have been interpreted in terms of a characteristic time, tau en , for electron cooling via electron-neutral collisions. Spatial measurements of I e indicated that no significant I e gradients exist in the plasmas during the periods over which cooling curves were obtained; it is also argued that there was no significant elevation of the gas temperature above the wall temperature during the afterglow. In all three gases good agreement is obtained with previously published data.