Physicists at Royal Holloway are building non-invasive instruments to measure electron bunches inside a particle accelerator that uses protons to drive plasma wakefields. The AWAKE experiment at CERN has already demonstrated that a proton bunch passing through plasma can create wakefields strong enough to accelerate electrons to high energy. The problem is that the original plasma source produced unstable wakefields, limiting energy gain and beam quality. The team is now testing new plasma sources, including a scalable discharge source, and a modified rubidium vapour source designed to stabilise wakefields over the full accelerator length. If successful, the next phase will use two plasma sources—one to micro-bunch the protons and another to accelerate a witness electron bunch—while maintaining beam quality. The ultimate goal is to show the process is scalable, meaning it can reach the conditions needed for practical use. This is fundamental science aimed at proving a new acceleration concept. If it works, it could eventually lead to more compact and powerful particle accelerators for applications in materials science, medical imaging, or cancer therapy—though those uses remain years away.
View original technical description
In AWAKE Run 1, the concept of proton-driven plasma wakefield acceleration was demonstrated experimentally with the acceleration of electrons to 2 GeV in wakefields created by the SPS protons. The long SPS proton bunch initially undergoes modulation in the plasma which splits it into microbunches which generate the strong wakefields. The micro-bunching was seeded with a laser pulse and in AWAKE Run 2a it was shown that it can also be seeded with an electron bunch. Now in Run 2b new plasma sources are being tested, including the scalable discharge source. Currently data is being taken with a modified rubidium vapour source which through control of the density profile is expected to lead to stable wakefields over the full length in contrast to the original plasma source in Run 1. With stabilised wakefields, we should be able to reach higher energy gain and have a more controlled experiment. This will lead towards the development of Run 2c which will need two plasma sources, one to micro-bunch the proton bunch and one to accelerate a witness bunch of electrons. The aim is to accelerate electrons to higher energy but also maintaining beam quality such as energy spread and emittance. The final goal, AWAKE Run 2d, is to show that the process is scalable by accelerating electrons in one, or both, of the scalable plasma sources demonstrating that they can reach the conditions (length, density, uniformity, etc.) needed for this acceleration. The team at Royal Holloway will develop instrumentation based on Cherenkov Diffraction Radiation capable of measuring the longitudinal electron bunch length in the presence of high intensity proton bunch, electron beam arrival time, and its position. Non-invasive nature will enable to continuously monitor the particle beam parameters.
Plain English summaries and category classifications on this site are generated by AI and may not perfectly reflect the original research.
Is something wrong? Let us know