RF breakdown test of diamond-loaded resonator for high gradient wakefield accelerator applications

• Dielectric-loaded structures represent an alternative approach to realize compact efficient accelerating schemes by means of electromagnetic wakes;
• Diamond has unique thermal, microwave, and electrical properties to be used as a loading material for acceleration structures;
• 8.6 kA peak current was transmitted through a diamond-loaded parallel plate resonator and induced an electric field as high as 0.3 GV/m;
• No evidence of catastrophic breakdown was observed — this corroborates the use of diamond for accelerator applications.

Dielectric-loaded accelerating structures (DLAs) for wakefield applications are an alternative to conventional corrugated metal structures. These structures have simple geometry, scale up to THz frequencies, and feature higher breakdown threshold. Diamond has been proposed as a loading material for DLAs due to a number of its unique thermal, microwave, and electrical properties. In this paper we report results of a wakefield breakdown test of a single crystal diamond resonator. A large, 72 nC, charge beam with 2.5 mm length, 8.6 kA peak current was transmitted through a diamond-loaded parallel plate resonator, and induced a standing wave with a 70 MV/m electric field strength. One of the diamond plates had a laser cut, 20 μm wide and 200 μm deep groove, that provided an additional ~ 5-fold field enhancement at edges of the groove resulting in an electric gradient as high as 0.3 GV/m on the surface of the groove. SEM and x-ray topography analyses before and after the test did not reveal any structural damage to the diamond resonator plates. This corroborates further promotion of diamond for high gradient wakefield acceleration at high repetition rates.