Speaker
Description
Understanding the microscopical phenomena behind vacuum arc generation is crucial for being able to control the breakdown rate thus improving the efficiency of many applications where breakdown generation is a limiting factor.
Statistical properties of breakdowns, such as pulses between breakdowns, breakdown waveforms and changes in vacuum pressure, are studied using a Large Electrode DC Spark System in Helsinki. In the system, copper electrodes separated by a 60 $\mu$m gap, are placed in near ultra high vacuum. Electric field up to 80 MV/m is pulsed across the gap, resulting in electric discharges - breakdowns.
Statistics are collected over thousands of breakdown events using electric field, pulse length, pulsing frequency or electrode treatment as variables. The statistical analysis is compared to the to the breakdown-induced features on the electrode surfaces which are imaged using various imaging and surface analysis techniques, such as white optical microscopy, white light interferometry and immersion ultrasonics.
The resulting statistics are used to classify the breakdown events in order to understand the underlying processes leading to them.
