Optimisation of PBG-Waveguides for THz-Driven Electron Acceleration

There is significant interest in novel accelerating techniques which can overcome the limitations of conventional radio-frequency (RF) based devices in terms of frequency, gradient, and footprint. Moving from RF to the terahertz (THz) frequency range, higher accelerating-gradient of high-energy particle beams can be achieved, as well as structure miniaturisation. Furthermore, in respect to the optical frequency range, THz allows for larger structures and better beam quality due to the increased capture phase-space. This work has been investigating the use of a 2D photonic-bandgap dielectric waveguide (PBG-W) for THz-driven electron acceleration which could potentially offer a good compromise between dispersion engineering and low losses. Dispersion characteristics of the accelerating mode are studied to achieve the best compromise between high accelerating field and effective accelerating bandwidth, assuming a broad-bandwidth THz driving pulse.