Experiment on Multipactor Suppression in Dielectric- Loaded Accelerating Structures with a Solenoid Field*

Efforts by numerous institutions have been ongoing over the past decade to develop a Dielectric-Loaded Accelerating (DLA) structure capable of supporting high gradient acceleration when driven by an external rf source. Multipactor is the major issue limiting the gradient that was revealed in earlier experiments. A theoretical model predicts a solenoid field within an optimal range of field strengths and applied to DLA structures may completely block the multipactor. To demonstrate this approach, an alumina based DLA structure was built and tested. We observed multipactor being successfully suppressed in the straight section of DLA structure with a certain strength of the solenoid field but enhanced in the dielectric taper, which is used for matching impedance in this particular design. Theoretical modeling and numerical simulation match with the experimental results well.