CO2-Laser-Driven Dielectric Laser Accelerator

In dielectric laser accelerators (DLAs), the electrons traverse through a channel whose structure period and transverse dimensions are comparable to the laser wavelength. If a 1-µm laser wavelength is used, this means the acceleration channel width must be less than or equal to 1 µm, which severely restricts the amount of charge that can be passed through the channel and places high demands on the electron beam emittance. Using a CO2 laser operating at 10 µm wavelength to drive the DLA enlarges the dimensions of the channel by 10 times. This increases the amount of charge that can be accelerated by orders of magnitude and eases the emittance requirements. As an additional improvement, we are proposing using an inverse free electron laser (IFEL), driven by a portion of the CO2 laser beam, to generate microbunches that are injected into the DLA. This allows maximizing the number of accelerated electrons and minimizing their energy spread, thereby improving the output beam quality. Other advantages of our approach include facilitating achieving phase synchronization of the microbunches within each DLA stage due to the longer laser wavelength and easing fabrication of the microstructures with acceptable tolerances because the structures are 10 times larger. To illustrate the scalability of this concept, we present a straw man design for a high-repetition-rate, high-peak-power CO2 laser system capable of driving multi-stage DLAs up to the energy and luminosity requirements for a future collider. Innovative features of this design include utilizing solid-state lasers (Fe: ZnSe) for pumping the CO2 amplifiers rather than conventional discharge pumping and recirculating laser power through the amplifiers to support high-efficiency, high-repetition-rate, multi-bunch acceleration.