Abstract
Understanding the microscopic phenomena behind vacuum arc ignition and generation is crucial for being able to control the breakdown rate, thus improving the effectiveness of many high-voltage applications where frequent breakdowns limit the operation. In this work, statistical properties of various aspects of breakdown, such as the number of pulses between breakdowns, breakdown locations and crater sizes are studied independently with almost identical Pulsed DC Systems at the University of Helsinki and in CERN. In high-gradient experiments, copper electrodes with parallel plate capacitor geometry, undergo thousands of breakdowns. The results support the classification of the events into primary and secondary breakdowns, based on the distance and number of pulses between two breakdowns. Primary events follow a power law on the log--log scale with the slope $\alpha \approx 1.33$, while the secondaries are highly dependent on the pulsing parameters.
Highlights
Grasping the underlying physical processes leading to electrical vacuum arc outbursts—breakdowns (BDs)—is important for many applications across various fields in modern science and technology
In CERN, there are continuous experiments done with the actual Compact Linear Collider (CLIC) accelerating structures, using 12 GHz rf pulses with repetition rates up to 400 Hz
The pulsing voltage was kept constant except immediately after each breakdown, when the asymptotic ramping described earlier was used to ramp up the electric field from one fifth to the target voltage in 2000 pulses (2100 for the setup in CERN)
Summary
Grasping the underlying physical processes leading to electrical vacuum arc outbursts—breakdowns (BDs)—is important for many applications across various fields in modern science and technology. The phenomenon occurs in devices that operate in (ultra) high vacuum and which are subject to high electric fields. Applications include vacuum switches and interrupters, vacuum arc metal processing, ion beam and pulsed sources, fusion reactors, satellites and radio-frequency (rf) particle accelerators [1,2,3,4]. Investigation on the origin of BDs has been underway for more than a century [1]. Theoretical and, more recently, computational studies have been performed over the decades in order to understand the phenomenon [5,6,7]. Several different processes have been suggested to explain the arc formation, but none of them have provided adequate analytic explanation [8]
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