THz-driven High Gradient waveguide dynamics and beamline design using machine learning

About the project

About the Project The acceleration of non-relativistic electrons has had intense interest in the last 9 years, with the effort to drive low-energy electrons to the relativistic regime for development of compact all-THz-powered light sources and electron diffraction. This started with demonstration of 1 keV energy gain with a field of 300 MeV/m and then the STEAM device [1] showed the feasibility of Terahertz-based electron accelerators with compact beams and 30 keV energy gain. This energy gain was soon pushed to 70 keV [4] with a 200 MeV/m field. Recently we showed through modelling [2] that tapered waveguides can provide control of electron beam quality (emittance, energy spread) for beams in this non-relativistic regime, opening the door to multi-MeV cascaded linacs. However, the attainment of MeV scale high quality beams from a non-relativistic source has so far proved elusive. For relativistic electrons, there have been proof of demonstrations at these energies from several groups (including ours). We showed two years ago [3] record THz-driven linear acceleration of relativistic 35.5 MeV, 20-100 pC electron beams, and advanced manipulation of the bunch to show de-chirping and the modulation necessary for the generation of micro-bunches. At CLARA, we have recently demonstrated [4] a more modest electron energy gain of a relativistic energy but demonstrated the key advances of timing jitter suppression in the THz cavities, beam quality preservation and the concept of THz diagnostics. We showed beam quality preservation is possible [5] in the THz acceleration process for technology applications (e.g. light sources, electron diffraction) and have some work in our group on the use of adiabatic structures to attain gradients up to 100 MeV/m from THz acceleration, aiming for 300 keV energy gain with 1 fC of charge. The aim of this PhD project is to demonstrate that a THz-driven high energy (MeV-scale) and high-quality beam is possible using very high gradient (up to GeVm scale) THz-driven structures, exploring the dynamics of the high gradient beam line, moving from non-relativistic energies to relativistic energies with at least fC of charge, performing experiments in the bunker on acceleration and investigating the complete facility concept and parameters. The project will exploit machine learning tools from the start to develop the solutions. This 3.5 year PhD project will explore the beam dynamics in these structures with the emphasis on acceleration up to GeV/m scale fields, novel structure design, transverse dynamics and beam phase space (emittance) preservation. The project will begin exploring of use of machine learning for structure and beamline design. The project will piece together synchronised THz-driven structures to build a large-scale facility to open the door to an ultra-compact THz-drive multi-MeV-scale linear accelerator. The project will also explore using the THz driven structures as a natural diagnostic for the evolving beam phase space and will benefit from data from our existing 100 keV electron injector bunker at Daresbury Laboratory and data we acquired at our 2022 CLARA accelerator run. These facilities are funded from the core grant of the Cockcroft Institute and are a benefit to this proposal. Objectives of the PhD: 1. Demonstrate that acceleration to multi-MeV high quality beam energies can be realised with THz acceleration in very short THz waveguides with high gradients, with beam control realised with synchronised THz compression. 2. Explore the concept and design of a higher energy THz facility built from such structures, specifically addressing the issue of beam quality preservation through multi-stage THz-driven structures. 3. Work as part of the CI THz group in the design and construction of a magnetic beamline to measure energy gain and beam properties in our structures. 4. Explore the applications of machine learning techniques to the design and optimisation of our beamline, structures and perform space-charge dominated particle tracking with such tools.

Research areas