Electron drift velocity and momentum transfer cross-section in caesium vapour

Electron drift velocities have been measured for swarms in caesium vapour by using a heat-pipe drift tube. The heat-pipe was used to both generate and to contain the caesium vapour. The electron transit times between the cathode and anode were measured for a variable gap separation by the induced charge method. Electron drift velocities were obtained as a function of E/N (ratio of electric field to vapour number density) for the range of 4<E/N<100 Td (1 Td=10 -17 V cm 2 ). The values are approximately 50% lower than those previously measured by Chanin and Steen in 1964. A momentum transfer cross-section, consistent with the present data, was derived by solving the Boltzmann equation.