Speaker
Description
Increasing accelerating gradients of accelerating structures promises higher particle energies, while reducing the total footprint and cost. Characterizing RF breakdown effects is crucial when pushing to higher gradients, as RF breakdown changes the reflected and transmitted power flow in traditional accelerators and can cause loss of operation and surface damage. In this work, we study low power RF cavity response in air under an induced arc to gain insight into RF breakdown dynamics. Arcs were triggered to study how RF breakdown in an upstream cavity affects the adjacent cavity for a distributed coupling structure. The test structure consists of two C-band cavities connected to a hybrid coupler with a high voltage (HV) probe inserted into the beampipe of the upstream cavity. Pulsed RF is fed into the hybrid, and an arc is triggered in the upstream cavity via HV pulses fed into the probe. A directional coupler allows forward and reflected measurements going in and out of the hybrid while a field probe coupled to the output load is also measured. Initial results show that the rf signals remain unaffected by the breakdown in upstream cavity, suggesting that RF breakdown effects in distributed coupling structures are localized and do not perturb the electrodynamics of the downstream cavities. Experiments under vacuum and nitrogen are planned and modeling is underway. Results from this study will be used for informed design of new accelerating structures.
Funding Agency
This work is supported by the U.S. Department of Energy Contract No. DE-AC02-76SF00515.
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