Combining high power lasers and relativistic electron beams to explore radiation, matter, and antimatter in strong fields

New high power laser facilities around the world are creating pulses of light with unprecedented electric and magnetic field strengths. There is an opportunity to drive relativistic electron beams through strong laser wakefields in a plasma and to use these electron beams to produce bright sources of polarised gamma rays and positron-electron pairs. The QED interaction between electrons at energies of above 100s MeV and coherent light at intensities of above 10²⁰ Wcm^-2 results in a multi-photon interaction that enters the strong-field regime and produces MeV-scale gamma-ray photons through inverse Compton scattering. These gamma-rays can be strongly polarised and can create positron-electron pairs.

In previous experiments, we have collaborated with York, Imperial College London, and Queen’s University Belfast, using some of the world’s highest power laser facilities to produce GeV-scale electron beams from laser wakefield acceleration and collide them with intense laser pulses. By reconstructing the spectrum of the energetic gamma rays and measuring the change in the electron beam energies, we characterised the strong-field interaction and explored this high-brightness light source. In other experiments, we drove the electron beam into high density converter targets, producing not only gamma-rays from bremsstrahlung, but also electron-positron and muon-antimuon pairs.

Proposed Work

By combining experiments with the stable electron beam at CLARA with results from GeV-scale electron beams at the highest power laser facilities, there is the opportunity to explore a much wider range of physics using the same techniques. These experiments would measure the production of bright x-rays and gamma rays in the transition from single-photon linear Compton scattering to multi-photon non-linear Compton scattering in the strong field regime.

During the PhD, the student will work on both simulations and experiments of laser wakefield acceleration and of the laser – electron beam interaction as part of the Cockcroft Institute’s particle accelerator programme. The student will be involved in the collaboration’s experiments on electron beams and Compton scattering both at high-power laser facilities around the world and at the CLARA electron accelerator at Daresbury. Simulations will be carried out using particle-in-cell codes (FBPIC, EPOCH) and Monte-Carlo codes, allowing the student to explore plasma accelerators as well as the physics behind the latest high-brightness light sources and the production of matter and antimatter in laser experiments.