16 Mar 2012







Compact Linear Accelerator for Research and Applications

Conceptual Design Report available here (PDF - 9824kB - link opens in a new window)

CLARA is an advanced electron accelerator test facility which we plan to upgrade to become a free electron laser (FEL) test bed in the future. The CLARA project that has three key objectives:

  • To be the European test bed for accelerator research and development. Bringing together international collaborations and investments to support the next big inspirational global science projects whilst increasing UK leadership and influence.

  • To enable the UK academic, industrial, and health sectors to develop new accelerator-based technologies, treatments, and frontier research for the benefit of the economy and society.

  • To pave the way for the UK to host an ambitious next-generation X-ray FEL light source user facility with world-leading capabilities that would advance the frontiers of knowledge across the physical an​d life sciences and support UK industry.


CLARA, which is located within the Electron Hall at Daresbury, will be a 90m long, low energy version of an advanced FEL light source. The underlying physics for the electron beam generation, acceleration and dynamics and the coherent light generation and manipulation via the FEL process are identical (and scalable) to that of European XFEL and SwissFEL, for example. CLARA will have a maximum electron energy of 250MeV and will be able to generate FEL radiation down to 100nm wavelength. The first phase of CLARA is already operational and has achieved beam energy of 50 MeV and bunch charges of more than 250 pC.


Each of the five countries which have built an XFEL has first built a prototype of similar scale to CLARA to prove new technologies, to lower the overall project risks, and to develop the team skills. The ambition of CLARA goes far beyond simply building an FEL prototype. We have designed CLARA to be able to prove several new FEL techniques for generating coherent light with characteristics far exceeding those available from today's XFEL facilities.​  XFELs are still in the early stages of development and exploitation. The intrinsic capabilities of these remarkable devices far exceeds their currently demonstrated performance. The UK has an opportunity to skip the current generation of XFELs and move directly to a world-leading facility with unique capabilities.


The 2017 STFC Accelerator Strategic Review and the 2016 STFC FEL Strategic Review have both confirmed that CLARA is an essential step that must happen before UK XFEL can proceed. Furthermore, the Accelerator Review has also identified additional capabilities that CLARA will bring to the UK to enable the accelerator community to play a leading role in accelerator, not just FEL, R&D internationally. Examples identified include the ability to use the high brightness electron beam directly for novel acceleration experiments such as plasma wakefield acceleration, dielectric wakefield acceleration, and THz driven acceleration schemes, all of which need access to a high brightness electron beam, such as CLARA, in order to make progress. Successful experiments using the already operational CLARA electron beam have been carried out in all of these areas and many more. 


Development of new accelerator technologies or techniques can only be made if they are demonstrated and tested on an actual accelerator. Progress globally is limited because such tests have to be carried out on accelerators which are dedicated to other purposes, such as particle physics or X-ray production. This restricts the time available for accelerator R&D and the degree of risk and innovation which can be trialed as the primary objective of these facilities is to serve their user communities. With or without UK XFEL, CLARA is already an excellent accelerator testbed which serves the academic and industrial accelerator communities full time and so these bottlenecks can be removed and rapid progress in R&D is now possible, reconfigurations of the machine permitted, and high risk-high reward technologies are being trialed safely. CLARA gives the UK accelerator community genuine leadership in accelerator R&D and is the envy of the world. The two UK accelerator institutes, which include seven of the leading universities active in accelerator research, are already contributing significantly to the ongoing development and exploitation of CLARA, including funding several PDRAs and PhD studentships, and they have ambitious plans for future R&D using the bright electron beam and FEL test-bed.



Further details can be viewed on the STFC website (link opens in a new window).