Cryogenics systems for the development of a THz-driven electron injector and linac

The investigators have developed technologies for the acceleration and streaking of relativistic electron beams with laser-derived terahertz (THz) pulses. These technologies, and the underlying concepts, have been targeted at application for ultrafast electron beam temporal control, and high-gradient acceleration with beam quality preservation that is an essential part of future high-energy accelerator technologies.

The programme has already established world leading status, and is placed at the forefront of a new and rapidly developing area. We were the first to demonstrate acceleration with fully relativistic beam [1], and our recent 2022 results have demonstrated all the essential functions carried out by conventional relativistic linac, but at the two orders higher frequency; staging, acceleration; energy spread control through phased acceleration; and a field gradient of 20 MV/m, comparable to that of operating accelerator facilities. Acceleration gradients exceeding 200 MV/m are now, with support of this grant, within reach.

In parallel to the development of acceleration of relativistic beams with THz, the Cockcroft Institute programme has established the facilities and concepts for a THz driven 'injector', the first stage where energies are taken from photocathode to relativistic energies.

The requested capital equipment, two closed-cycle cryostat systems, are required for cooling of the PP-LiNbO3 THz sources. Integration of the cryogenic-cooled THz sources into our existing research programme will ensure that we remain the forefront of a rapidly developing field. We will be well placed to prove the capability of an integrated THz-driven accelerator with unprecedented capability for femtosecond electron beam acceleration and control, and acceleration gradients exceeding that of conventional RF accelerators.