Development of a Transverse Mode Damped Dielectric-Loaded Accelerating Structure

As the dimensions of accelerating structures become smaller, or as beam intensities become higher, the transverse wakefields driven by the beam become quite large, even for a slight misalignment of the beam from the geometric axis. These deflection modes can cause inter-bunch beam breakup and intra-bunch head-tail instabilities along the beam path. This project will design a cylindrical dielectric-loaded accelerating structure that has a few longitudinal slots distributed along the copper wall of the dielectric loaded accelerator (DLA) structure, so that the transverse modes are not able to be confined inside the dielectric and vacuum channel. The energy of the transverse modes that propagate past the segmented boundary is absorbed in a SiC slab buried in the grooves. The accelerating mode can maintain good propagation characteristics along the structure with only a slight sacrifice of power loss. In Phase I, a 7.8GHz transverse mode damped DLA structure will be fabricated and bench tested. A detailed simulation of the beam dynamics inside the structure will be performed using the 3-D MAFIA code. Commercial Applications and other Benefits as described by the awardee: The transverse-mode-damped DLA structure could form the basis of a practical dielectric based accelerator for immediate use in high energy physics.