Speaker
Description
Vacuum arcs are a common problem for electrostatic septa equipment in particle accelerators. Observations during the Large Electron Positron (LEP) era showed an increase in the High-Voltage Breakdown Rate (HVBR) of electrostatic separators due to Synchrotron Radiation (SR) striking the equipment. As part of the studies for CERN's next accelerator, the Future Circular Collider (FCC-ee), an Electro-Magnetic Separator (EMS) is being designed. This device will feature two high-voltage electrodes under vacuum, and will be exposed to SR from the arc region of the collider. In an effort to assess the impact of this SR irradiation on the electrodes' HVBR --- and thus on the overall failure rate of the equipment --- an experiment has been set up to study the dependence of HVBR on X-ray irradiation. The experimental setup, the Large Electrodes System (LES), consists of two electrodes, separated by an adjustable gap, mounted inside a cylindrical vacuum vessel, with an X-ray source attached. Pressure, electric field and breakdown rate are monitored, and a set of cameras is installed to localise individual breakdowns on the electrode surface. This experiment is currently underway at the CERN Septa Laboratory, where the electrodes are conditioned to fields above 65 MV/m and HVBR and field emission measurements are performed both with and without X-ray irradiation. We present the experimental approach and the measured dependence of HVBR on this irradiation.
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