CERN Accelerating science

Game-changing plasma accelerator

Ultra-compact, powerful particle accelerators for research, healthcare, and industry have come a step closer with the completion of the EuPRAXIA design study, showing that plasma acceleration provides a viable alternative to established accelerator technologies.

Currently, the size and cost of accelerator facilities restrict access to this powerful technology, as EuPRAXIA Coordinator Dr. Ralph Assmann from DESY in Germany explains:

“In addition to their important role in fundamental research, particle accelerators are used throughout medicine and industry for cancer therapy, the production of radioisotopes for medical diagnostics, for cargo inspection, food sterilization, and for facilitating advances in the electronics industry. However, the energy achievable with the existing technology is limited by the physical size of the accelerator. Few organisations have the space or budget for a high-energy accelerator because of the size and cost.”

The accelerator designed by EuPRAXIA will use lasers or electron beams to propel electrons forward on a plasma wave. The result will be a much smaller, affordable accelerator that uses accelerating gradients up to 1,000 times higher than what can be achieved with RF technology.

Simulation of a plasma wakefield with ALaDyn PIC code. (Image credit A. Marocchino, INFN-LNF)

Professor Carsten P Welsch, EuPRAXIA’s Communication Lead and Head of Physics at The University of Liverpool, continues: “EuPRAXIA is a game-changer with the potential to offer accelerators for everyone, everywhere. It can make existing applications more accessible and affordable so that future accelerators could be installed in university campuses, hospitals, and factories and offer the opportunity for new applications that we can currently only dream about.”

The design of EuPRAXIA includes a facility for pilot users so that researchers can explore the full potential of the accelerator for the first time. The foreseen electron energy range of 1-5 GeV and its performance goals will enable versatile applications in various domains, e.g. as a compact free-electron laser (FEL), compact sources for positron generation, table-top test beams for particle detectors, as well as deeply penetrating X-ray and gamma-ray sources for material testing. An area of particular interest is to be able to produce ultra-fast electron and photon pulses that are highly relevant for studying biological and chemical processes.

Over the last four years, scientists have evaluated nine different scenarios for creating high-quality beams using plasma acceleration. In the end, several highly performing accelerator designs have been found as an optimal way forward and will be integrated into multiple beamlines using laser- and electron-beam-driven plasma wakefield acceleration.

Once a factor-3 reduction in facility size has been demonstrated by EuPRAXIA, a miniaturization process towards even more compact designs will be pursued. A reduction factor of 10 and even 20 for the accelerator itself seems feasible at high beam energy. 

Rendering of the two-stage, very low energy spread plasma accelerator developed for the EuPRAXIA facility. The open tubes show the paths of the laser pulses (red lines) that drive the plasma wakefields in the vacuum chambers. (Image credit: EuPRAXIA)

The EuPRAXIA design is the result of four years of work by leading scientists from 16 laboratories and universities from five European countries, with a further 25 partners globally. It has been coordinated by DESY and funded by the EU’s Horizon 2020 programme. Participation in EuPRAXIA provides a unique opportunity to be at the forefront of research, which will revolutionise the use of accelerators.

The publication of the conceptual design report is an important milestone towards the realisation of the world’s first plasma accelerator with superior beam quality. Dr. Assmann explains: “EuPRAXIA has involved, amongst others, the international laser community and industry to build links and bridges with accelerator science. The proposed EuPRAXIA infrastructure aims at the construction of an innovative electron accelerator using laser- and electron-beam-driven plasma wakefield acceleration that offers a significant reduction in size and possible savings in cost over current state-of-the-art RF-based accelerators. Our CDR presents a fascinating concept for a next-generation facility.”

More information about EuPRAXIA and the Conceptual Design Report can be found on the project website:

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EuPRAXIA Design Study comes of age

As particle physics demands ever more powerful accelerators, the tendency is to go bigger. Dr Ralph Assmann, a leading scientist at DESY believes a completely different approach is needed. Plasma accelerators can be powerful, yet up to 1,000 smaller than conventional accelerators.

Driven by lasers or particle beams, the density oscillations in a plasma can sustain much larger fields, overcoming the breakdown limit of RF cavities. Any electrons trapped in the wake of the plasma wave, may be accelerated up to several GeV in a few millimeters. The effect is known as wakefield acceleration.

In recent years, the energies accessible to plasma wakefield accelerators have risen sharply. Scientists like Dr Assmann want to increase these energies, but also to improve the stability and quality of the electron beams coming out of the accelerator. This would make plasma accelerators suitable for particle physics but also a host of other applications like drivers for Free Electron Lasers.

Participants at the 3rd EuPRAXIA Collaboration Week. (Credit: QUASAR Group)

Dr Assmann is coordinating the project EuPRAXIA to come up with a design for the world’s first plasma wakefield accelerator with an energy of 5 GeV that can actually be used for research. That may not seem as an impressive energy but as Dr Assmann points out; you have to walk before you can run.

‘Clearly, plasma accelerators are the logical long-term solution for advancing the energy frontier in particle physics,’ he said. ‘But it will require a realistic and sustained approach.’

The EuPRAXIA consortium, comprising 40 laboratories and universities is addressing key questions, like driving the plasma with a laser or a particle beam, accelerating the electrons from the plasma or using an external injector, and employing a single stage or a multi-staged approach. The conceptual design report is expected to be completed towards the end of next year.

In order to produce a fully integrated and coherent report the frequent interaction between the work groups designing the different elements of the facility is essential. Moreover, as the layout of EuPRAXIA starts to take shape, it is time to involve the external stakeholders: the companies which will supply the technology, the scientists who will use the facility, and the students who will run it in the future.

Scientists from across Europe gathered in Liverpool to discuss the future of plasma accelerators. (Credit: QUASAR Group)

The latest of the EuPRAXIA collaboration meetings took place in Liverpool on 4 – 6 July 2018. The last day of the meeting took the form of a public event at the Liverpool Arena and Convention Centre. The Symposium ‘Quantum Leap Towards the Next Generation of Particle Accelerators’ was a special occasion to showcase the progress made within the EuPRAXIA Design Study alongside the future of plasma accelerators, advanced laser technology, and industry opportunities gathering together scientists, students, and representatives from over 40 companies.

Professor Carsten Welsch, EuPRAXIA’s Director of Communication and Head of the Liverpool Physics Department, said: ‘The collaboration week allowed a critical assessment of the research progress made across all of EuPRAXIA’s scientific work packages. On the other hand, the Symposium was ideal to present the aims and opportunities of EuPRAXIA to a much wider audience.’

The morning session of the Symposium featured talks from research leaders about the science and technology of plasma accelerators. Hands-on demonstrations helped to explain students how this new type of accelerators works and how the particle beams can be optimized. A poster session showcased the results from EuPRAXIA research to date.

‘Marshmallow waves’ helped to explain how this new type of plasma wakefield accelerator works. (Credit: QUASAR Group)

Oliver Burns, one of the 120 high school students who attended the Symposium commented: ‘This science is at the forefront of innovation, and it would be incredible to be a part of advancing the world we live in.’

In the later part of the day the event focused more on the importance of industry-academia collaboration for large scale research infrastructures. It included an industry exhibition highlighting the latest technologies and market-ready products, as well as talks about the wide range of applications in which accelerators find use.

Industry exhibition at the Symposium. (Credit: QUASAR Group)

Dr Assmann said: ‘EuPRAXIA represents the next generation of accelerators that will enable fantastic new applications. To pave the way for such a novel facility, we need to work together across research disciplines, countries and sectors.’ Quoting John Lennon, he added: ‘A dream you dream alone, is only a dream. A dream you dream together is reality.’

All the talks from the Symposium are available online and can be watched here:

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EuPRAXIA marks two years of research into plasma accelerators

The Horizon 2020 Project EuPRAXIA has just passed the halfway mark. The consortium led by DESY is preparing a conceptual design report of a highly compact and cost-effective European facility with multi-GeV electron beams using plasma as the acceleration medium. The accelerator facility will be based on a laser and/or a beam driven plasma acceleration approach and will be used for photon science, high-energy physics detector tests, and other applications such as compact X-ray sources.

The EuPRAXIA consortium has held its second Yearly Meeting and Collaboration Week from 20th to 24th November 2017 at the Instituto Superior Técnico in Lisbon. All partners gathered to discuss the status of each of the work packages and of the project as a whole. The Collaboration Board of EuPRAXIA approved the incorporation of Queen’s University Belfast (UK) and the Ferdinand-Braun-Institute of Berlin (Germany) as associated partners. With these new additions, the number of partners in EuPRAXIA now rises to 40.

The event in Lisbon was also the occasion for the first meeting of EuPRAXIA’s Scientific Advisory Committee (SAC). The SAC, composed of eight international experts in laser and accelerator science, was in charge of assessing the status of the project and providing a set of recommendations.

The Scientific Advisory Committee of EuPRAXIA presenting its conclusions in Lisbon (Image: EuPRAXIA)

Coordinator Ralph Assmann and the principal researchers of EuPRAXIA gave a summary of the status of the project and their respective work packages.

Current research within the consortium aims to improve the beam quality and to demonstrate the benefit of size and cost of a plasma accelerator versus established radio frequency (RF) technology.

Beam quality is essential in order to show that plasma accelerator technology is usable. In EuPRAXIA, two approaches are being used to address the beam quality. The first is to improve the technical components and plasma accelerator schemes already producing GeV class beams; this includes improved laser technology and feedback loops. The second is to start with a high-quality beam from a small RF injector and boost it to high energy. The latter approach is fully stageable, offering a path to high energy while the starting beam quality is assured. However, it brings out new issues, like sub-femtosecond beam synchronization, for which new solutions are needed and new ideas are being implemented. 

The project has identified nine different technical scenarios to achieve the target performance of the EuPRAXIA facility, defining the baseline parameters for the operation of lasers, RF injectors, and plasma accelerators. Several partners are assessing the viability of the different schemes through advanced start-to-end simulations and experiments at various European facilities.

The consortium has also made significant progress in developing the applications where a plasma-based accelerator would have a large impact, namely as a driver for a Free Electron Laser and as a test bed for high-energy physics detectors. 

EuPRAXIA is now ready to take on the second iteration of its general layout and start evaluating the cost construction and operation of the facility. The proposed solutions must offer significant benefits with respect to RF-based accelerators, e.g. fitting constrained spaces and being cost-effective, including having lower operational costs.

The design study is site independent, although five possible sites have been discussed. The construction of EuPRAXIA will be decided after 2019, and its location will be based on the facilities and expertise available at all the supporting laboratories. Even though the facility would be built in one central site, all the project partners would commission parts at their local facilities.

The final conceptual design report, which will include a detail implementation model, will be submitted in October 2019 and if construction is approved it could start operations as soon as 2025.

Although there are still major challenges ahead, the progress made in the first half of the project gives us the confidence to look forward to the delivery of an excellent Conceptual Design Report for a highly compact and cost-effective plasma accelerator facility with industrial beam quality.

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Physics of Star Wars: Science or Fiction?

Light sabres, hyper speed and droids – how do they all connect with the latest accelerator research? With the imminent launch of “The Last Jedi”, Professor Carsten Welsch, Head of Physics at the University of Liverpool and Head of Communication for the Cockcroft Institute, has explored the “Physics of Star Wars” in an event on 27th November designed to introduce cutting-edge accelerator science to hundreds of secondary school children, undergraduate and PhD students, as well as university staff.

The day started with a lecture which first presented iconic scenes from the movies to then explain what is possible with current technology and what remains fiction. For example, a lightsabre, as shown in the film, wouldn’t be possible according to the laws of physics, but there are many exciting applications using lasers. There is a link to advances in lasers and laser acceleration being studied by an international collaboration within the EuPRAXIA project. This programme is developing the world’s first plasma accelerator with industry beam quality. It uses a high intensity laser pulse to drive an electron beam and accelerate this to high energies. Applications in science or industry that are close to a light sabre include for example 3D printing of metals and laser cutting.

Professor Welsch said: “In the very first movie from 1977, the rebels have used proton torpedoes that make the Death Star explode as their lasers wouldn’t penetrate the shields. I linked that to our use of ‘proton torpedoes’ in cancer therapy. Within the pan-European OMA project we are using proton beams to target something that is hidden very deep inside the body and very difficult to target and destroy.”

 OMA Fellow Jacinta Yab explaining the use of ‘proton torpedoes’ in cancer therapy (Image credit: QUASAR Group)

 The light and dark side of the Force in Star Wars was an ideal opportunity to talk about matter and antimatter interactions which are currently being explored at CERN’s AD and ELENA storage rings, as well as within the brand-new Marie Sklodowska-Curie research network AVA. Finally, participants learned about how high energy colliders, such as the LHC, its high luminosity upgrade or a potential Future Circular Collider (FCC) as it is being studied within the EuroCirCol project, can provide fantastic opportunities to study the force(s).

High school students participating in hands-on activities during ‘Physics of Star Wars’ event. (Image credit: QUASAR Group)

After the lecture, all participants were given the opportunity to understand the science behind Star Wars through numerous hands-on activities in the university’s award-winning Central Teaching Laboratory. This included laser graffiti, augmented reality experiments with Star Wars droids and virtual accelerators using AcceleratAR, and even two full-scale planetariums which fully immersed participants into the world of Star Wars, deflecting charged particle beams using Helmholtz coils.

Professor Welsch and members of his QUASAR Group had the kind permission of Lucasfilm to use film excerpts; these were complemented by Lego Star Wars models, a real cantina as found in the movies, storm troopers and even Darth Vader himself! Many photographs from the exciting day can be found on Twitter at

Lucasfilm had no involvement in the preparation or delivery of the event which was organised only by staff and students from the University of Liverpool.


Header image: Prof Carsten Welsch presenting the ‘Physics of Star Wars’ (Image credit: QUASAR Group)

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