An Inverse-Cherenkov Particle Accelerator Driven by a Focused Cherenkov Terahertz Pulse From a Ring-Shaped Electron Bunch

The compact particle accelerator with high energy gain has been a quest for researchers. Using dielectric acceleration structures to replace metallic ones and shortening the duration of electromagnetic driving pulses are effective ways to increase the acceleration gradient and then shrink the size of the particle accelerator. Here, we propose a set of all-dielectric particle accelerator schemes driven by terahertz (THz) pulses. It uses a ring-shaped electron bunch with a high bunch charge to drive a modified dielectric cylinder to generate a high-intensity THz pulse via the focused Cherenkov effect, which is then used to accelerate the witness bunch propagating along the axis of the dielectric cylinder through the inverse-Cherenkov effect (ICR). These proposed schemes are capable of accelerating particles from the subrelativistic to relativistic regime on a millimeter-to-centimeter structure, paving the way for a compact, even tabletop megaelectronvolt-level particle accelerator.