Numerical investigations into a THz-driven dielectric accelerator with a Bragg reflector

Abstract

Abstract Using THz pulses to generate an accelerating field in a dielectric loaded accelerator structure is a promising way to mitigate the disadvantages of RF and Laser accelerator structures. This paper proposes an energy efficient side-coupling dielectric single-grating structure accompanied with a multi-layer Bragg reflector that is designed for THz pulse operation. To show the comparative advantages of the new design, we also numerically investigate a single-side coupling THz-driven dual-grating structure which is composed of Silicon Dioxide (SiO2). Simulation results show that the reflector structure effectively manipulates the THz field compared to dual-grating structure, not only boosts the field strength in the accelerating channel, but also optimizes the field distribution and generates a periodic field reversal to achieve better phase synchronicity for relativistic particles, thereby increasing the accelerating gradient by more than 40%. It is also found that the energy-recycling capability of a Bragg reflector highly depends on the operating THz pulse duration and beam channel width. Choosing a longer pulse duration and setting a narrower beam channel width with an optimum pillar height can increase the single pulse efficiency by more than 70% compared to the bare dual-grating structure.