How do we control the shape and time structure of our very short bunches using THz-driven structures?

About the project

About the Project Particle accelerators are powerful tools that have driven major discoveries in physics, from finding the Higgs boson to developing new materials. Traditional accelerators, such as the 27 km Large Hadron Collider at CERN, are extremely large and costly, which limits how widely they can be built. New concepts like laser–plasma accelerators (LPAs), which exploit high electromagnetic fields in plasmas created by lasers, can shrink the size of an accelerator from kilometres to just centimetres, but the electron beams they produce often have a large energy spread (variation in particle energies), making them difficult to use in many applications. This PhD position will explore using high frequency coherent light (THz radiation) produced from a laser to accelerate and manipulate charged particle beams using lined cylindrical tube called a waveguide, into which both the radiation and the electron beam are focused. There has been much interest in the topic in the last few years, in which our group has been central. Studies with both relativistic and non-relativistic beams demonstrate effective energy gain and improving beam quality, though achieving high-quality MeV-scale beams remains especially challenging for nonrelativistic cases. In this project we will not explore the energy frontier but look to use THz-driven structures to control the quality, phase space shape and time structures of our beans. We shall exploit THz-driven structures to manipulation and control the beam and its phase space properties. This is important as techniques are developed to accelerate particles to higher energy but with a large distribution in phase space, for example in laser-plasma accelerators (LPA). This PhD project will seek to make the bunches produced by novel accelerator useful for precision experiments and for large scale luminosity generation. The project will explore phase space manipulation including energy spread reduction using active de-chirping, which will control the energy spread in bunches produced by LPAs. This will enable the devices to deliver high quality bunches and solve some of the inherent problems we have with divergent bunches from plasma-based techniques. We will also explore longitudinal phase space partitioning, using THz-driven energy chirping to divide long bunches into mini-bunch trains. These concepts will be explored theoretically, computational and experimentally as part of the THz group. The aim of this PhD project is to demonstrate the use of THz structure to manipulate and control short duration (~10s fs) bunches. This has relevance to the control of phase-space arising from LPA. We shall explore structures to manipulate the bunch’s chirp to actively de-chirp the phase space and reduce the energy spread and explore THz driven long bunch manipulation to generate trains of short bunches. The ideas will be tested at experiments at ELI. The focus will be on the beam dynamics, lattice design and validation at facilities such as ELI. Objectives of the PhD: 1. Demonstrate the short bunch control of particle longitudinal phase space using active de-chirping structures, designed to considerably reduce energy spread of LPWA-accelerated bunches. 2. Integrate THz-driven active de-chirping into realistic LPA lattices. 3. Demonstrate the use of THz-induced energy chirp to modulate a long bunch into a series of mini-bunches, generating a bunch train of electrons. 4. Show how we can reconstruct the phase space of bunches using THz manipulation. 5. Test the ideas of phase space manipulation at ELI. The project is computational and experimental in nature, involving work on developing simulation codes, using codes such as CST, FBPIC and GPT, and custom group-codes and joining our experimental team and perform experimental work at ELI. You will join the Cockcroft Institute of Accelerator Science and Engineering, the University of Manchester and the Accelerator Science and Technology Centre, benefiting from the training programmes and support of all institutions. Full training, mentoring and supervision will be given by the supervisory team. Funding and eligibility: Upon acceptance of a student, this project will be funded by the Science and Technology Facilities Council for 3.5 years. This consists of a tax free stipend at UKRI rates, university fees at the home (UK) rate, plus support for travel to conferences and workshops. A full package of training and support will be provided by the Cockcroft Institute, and the student will take part in a vibrant accelerator research and education community of over 150 people. An IELTS score of at least 6.5 is required. Contact for further information: Prof. Rob Appleby robert.appleby@manchester.ac.uk How to apply: Apply at the Cockcroft Institute PhD webpage . For full consideration for funded awards, please apply by Jan 31st 2026. Anticipated Start Date: October 2026 for 3.5 Years

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