Vacancies within the QUASAR Group

PhD Projects

Ultra-high Gradient Acceleration using Carbon Nanotube Arrays

Project Description:

Standard radiofrequency (RF) accelerator technology is limited to gradients of the order of 100 MV/m. For instance, future linear electron/positron colliders based on RF technology, such as the International Linear Collider (ILC) or the Compact Linear Collider (CLIC), are designed to produce acceleration gradients of between 30 MV/m (ILC) and 150 MV/m (CLIC, 30 GHz frequency operation mode). There machine must therefore be tens of kilometres long to reach the desires beam energies, 125 GeV (ILC) and 1.5 TeV (CLIC).

R&D into novel acceleration techniques towards more compact machines has made tremendous progress in recent years. For example, plasma wakefield acceleration (PWFA) techniques based on gaseous plasma have shown to be able to obtain gradients up to approximately 100 GV/m. On the other hand, solid-state based structures may allow us to go even beyond this limit and obtain ultra- high gradients on the order of 1-10 TV/m.

Solid-state plasma wakefield acceleration using crystals was proposed in the 1980’s and 1990’s by T. Tajima and others as an alternative particle acceleration technique to obtain TV/m acceleration gradients. However, it has not been experimentally demonstrated yet. In recent years, new efforts have been focused on the feasibility study of channelling acceleration of particle beams using carbon-based nano-crystals such as carbon-nanotubes (CNT) or metallic nanotube structures, e.g. porous alumina. CNT configurations may be advantageous over typical crystal media like silicon because of their large degree of dimensional flexibility and thermo- mechanical strength, which could be suitable for channelling acceleration of MW beams. For example, CNTs allow transverse acceptances of the order of up to 100 nm, i.e. three orders of magnitude higher than a typical silicon channel. Therefore, CNTs might be used for wakefield acceleration using either a beam or a laser as driving source.

This project proposes to investigate in detail the use of CNTs for channelling acceleration and its potential application to build more compact accelerators and X-ray radiation sources. It is based on earlier studies done by the supervisory team. This includes the design and performance of a proof-of-principle test wakefield particle acceleration in CNT arrays. Measurements will be done at different accelerator facilities, including VELA/CLARA at Daresbury, the SwissFEL at PSI, and CLEAR at CERN. These machines operate in a similar range of beam energy of approximately 200 MeV. In all cases we expect to operate with short bunches on the order of 0.1 ps, and the beam can be modulated by a bunch compressor chicane. If necessary, even shorter bunches could be obtained at the sub-fs level via bunch slicing in the magnetic chicane, using a collimator. The theoretical and simulations results will guide the design of the experimental studies.

The successful candidate will have or expect to obtain a first or upper second-class degree or equivalent (e.g. MPhys, MSci) in physics or chemistry. Experience of accelerator physics, Particle-In-Cell (PIC) programming and solid-state physics is an asset.

You will be based at the Cockcroft Institute, which is the UK’s largest educator of accelerator science and technology PhD students, and offers exciting studentships in physics, engineering and other disciplines.

Potential applicants are encouraged to contact Prof. Carsten P. Welsch ( or Dr. Javier Resta-Lopez ( for more information. This position will remain open until filled.

Funding and eligibility: Upon acceptance of a student, this project will be funded by the Science and Technology Facilities Council for 3.5 years; UK and other EU citizens are eligible to apply. 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.

How to apply:

Anticipated Start Date: October 2019 for 3.5 Years


Performance optimisation of accelerators using machine learning techniques

Project Description

Reliable and realistic accelerator models are essential for the efficient control and performance optimisation of any accelerator. They need to be coupled with a robust beam control system to guarantee high beam quality and stability and reduce losses.

To meet these requirements, this project will investigate the use of Machine Learning (ML) techniques to build predictive models for a multivariate optimisation of an accelerator/beam line. The goal is to create algorithms that find and correct anomalies in different kinds of data, e.g. orbit data, power supplies, beam losses, etc. These ML tools will then provide excellent and efficient tools to tune beam optics, improve operation and provide the required beam parameters for specific experiments.

This first part of the project will combine input from the established codes MAD-X, G4beamline and CST studio. This work will familiarize the student with geometry and boundary condition definition, as well as the structure and limitations of all individual codes. The combined approach will allow performing high precision simulations taking into account e.g. fringe field effects and inhomogeneities due to geometrical factors. Models will then be established of the different CERN rings and enhanced by implementing genetic algorithms which the group is already applying for the optimization of synchrotrons (SOLEIL) and PERLE. These will then be utilised for machine optimization studies.

Funding and eligibility: The project is offered within the Liverpool Centre for Doctoral Training in Big Data Science (LIV.DAT). You will benefit from a comprehensive postgraduate training in data science provided within the centre whilst at the same time also having the opportunity to follow the Cockcroft Institute lecture program on Accelerator Science. The project is funded for full 4 years and builds on an existing collaboration with CERN. In Liverpool, you will be expected to do some undergraduate demonstrations as part of the studentship. The possibility to spend years 1 and 4 at UoL/CI and years 2+3 at CERN can be discussed as part of the project setup. Project offered, subject to funding. UK and other EU citizens are eligible to apply. In case your mothertongue isn't English, an IELTS score of at least 6.5 will be required.

How to apply:

Anticipated Start Date: October 2019 for 4 Years


Fellowship opportunities

‌We invite expressions of interest for a number of prestigious Fellowships and grants, including UKRI Future Leaders FellowshipsERC Starting and Consolidator Grants, Marie Curie Fellowships, and STFC Rutherford Fellowships all year around.

These funding schemes offer outstanding supporting and developing opportunities for time frames between 2-5 years and are an ideal platform for those who have already demonstrated their potential as outstanding researchers. We can provide access to world-class research infrastructure at the Cockcroft Institute/University of Liverpool and help you develop your proposal into a competitive bid. The stimulating environment within the QUASAR Group will be the perfect basis to turn your research ideas into reality.