Radio frequency breakdown rate is a crucial performance parameter that ensures that the design luminosity is achieved in the CLIC linear collider. The required low breakdown rate for CLIC, of the order of ${10}^{-7}\text{breakdown}{\text{pulse}}^{-1}{\mathrm{m}}^{-1}$, has been demonstrated in a number of 12 GHz CLIC prototype structures at gradients in excess of the design $100\mathrm{MV}/\mathrm{m}$ accelerating gradient, however without the presence of the accelerated beam and associated beam loading. The beam loading induced by the approximately 1 A CLIC main beam significantly modifies the field distribution inside the structures, and the effect on breakdown rate is potentially significant so needs to be determined. A dedicated experiment has been carried out in the CLIC Test Facility CTF3 to measure this effect, and the results are presented.

• Received 16 February 2018

DOI:https://doi.org/10.1103/PhysRevAccelBeams.21.102001

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Published by the American Physical Society