High voltage vacuum insulation in crossed magnetic and electric fields

This work discusses research on high-voltage vacuum insulation conducted using several test stands to support development of an improved electrostatic deflector for the Chalk River superconducting cyclotron. One test stand uses a magnetic field of 0.5 T normal to the electric field. It is instrumented with isolated electrodes above and below the negative high-voltage electrode, an isolated anode and monitors of X-rays, light emission and residual gas analysis. This test stand has been used to study high-voltage conditioning and microdischarge phenomena for gaps from 1 to 3 mm. Copper and stainless steel with a variety of surface treatments have been used during these experiments. Results from this research have led to improved understanding of high-voltage conditioning in “practical” vacuum systems that reach about 2×10^-7 torr with no bakeout capability. DC electric fields as high as 67 kV/mm (100 kV across a 1.5 mm gap) have been obtained with vacuum degassed and electropolished copper electrodes. Other surface preparations have been tested and results are compared