Oxford physicists, working as part of the international the Hybrid Asymmetric Linear Higgs Factory (HALHF) collaboration, have demonstrated plasma-wakefield acceleration in the UK for the first time – a breakthrough that could dramatically reduce the size, cost and energy demands of future particle-accelerator facilities.
The experiment took place at the CLARA test facility at STFC Daresbury Laboratory, where a team from the University of Oxford, working alongside colleagues from the universities of Oslo and Manchester, DESY, and the STFC Accelerator Science and Technology Centre (ASTeC), successfully integrated plasma-wakefield acceleration (PWFA) modules into CLARA and used them to produce electric field strengths of more than one gigavolt per metre – orders of magnitude greater than those achievable in classical accelerators.
Plasma-wakefield acceleration works by driving intense plasma waves using a particle beam; charged particles riding those waves experience enormous accelerating forces, which in principle allows the technology to deliver the same performance as a conventional accelerator in a much smaller space. The HALHF project is developing a design for a future particle collider that combines established radiofrequency cavities with novel PWFA modules, aiming to exploit the strengths of both approaches.
The results from this Phase 0 experimental run also demonstrated the ability to focus electron beams with fields greater than 100 tesla per metre, while maintaining beam quality through the high-gradient plasma. These are key performance metrics for any future deployment of the technology at scale.
The findings mark a significant step forward for the broader physics community. There is wide agreement that the next major particle-physics facility should be an electron–positron collider – a so-called Higgs factory – capable of studying the Higgs boson in greater detail and searching for physics beyond the Standard Model. Several competing designs exist, but all current proposals based on classical accelerator technology face substantial challenges of cost, land use and energy consumption. PWFA offers a potential route to a more compact, affordable alternative. 'It's widely accepted that an electron–positron Higgs factory, with its "exceptionally clean" experimental conditions, will reveal the new physics that we know must exist beyond the Standard Model,' says Professor Richard D'Arcy of the John Adams Institute for Accelerator Science at the University of Oxford.
Oxford has been central to the HALHF project from its inception: the collaboration was conceived by three scientists, two of whom – Professor Brian Foster and Professor D'Arcy – are academics at the John Adams Institute, with the third being Professor Carl Lindstrøm of the University of Oslo. The collaboration now comprises more than 50 scientists and is coordinated by Foster, D'Arcy and Lindstrøm. Professor D'Arcy served as principal investigator for the HALHF@CLARA experimental programme, coordinating the 18 domestic and international scientists involved, with the majority of dedicated personnel funding provided by the John Adams Institute.
'The first experimental period at CLARA earlier this year was extremely successful, essentially going from zero to state-of-the-art in only five weeks,' says Professor D'Arcy. 'The next step is to leverage this strong foundation to make the next exciting and necessary leaps in plasma acceleration. This will take the form of a multi-year programme that we hope will begin later this year.'
Follow-on experimental runs at CLARA are planned for later this year, with the team intending to tackle two outstanding challenges in plasma acceleration: staging multiple PWFA modules in series to reach very high energies, and operating the plasma modules thousands of times per second to achieve the luminosity – the collision rate – needed for a viable collider. The HALHF collaboration has also submitted its contribution to the European Particle Physics Strategy Update 2026, as part of a wider push to secure greater resources and international coordination for plasma-acceleration research.