Capacitive Gap Distance Control in Pin-Plane electrode DC Spark Systems at CERN

Capacitive inter-electrode gap distance measurement and control has been implemented into DC Spark System II, used by the DC Spark Study to conduct vacuum electrical breakdown experiments as a complement to breakdown experiments in RF accelerating structures. The implemented system is described, along with the calibration measurements needed for its use. Sources of experimental uncertainty in gap distance were investigated. It was found that the lowest relative uncertainty of gap distance the system is capable of achieving is 3%, or an absolute uncertainty of about 1 μm for a 30 μm gap.