Avalanche current measurements at high SF/sub 6/ pressure

In this work a successful solution is found for measuring the avalanche induced current at atmospheric SF/sub 6/. Originally, the current was measured in a modified pulsed Townsend setup where the electric field is almost uniform at the cathode and decreases rapidly near the anode. This system was suitable for studying discharge development at low SF/sub 6/ pressure. At atmospheric pressure, however, no avalanche could be detected up to breakdown. This is because, at high pressure, the breakdown field is close to the critical field. To overcome this situation, a different Laplacian field distribution has been considered in which the field at the cathode is enhanced to increase avalanche growth and detectability. Using this field configuration, measurements confirmed the possibility of producing detectable avalanches at atmospheric SF/sub 6/ pressure.