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Report

Teaser, summary, work performed and final results

Periodic Reporting for period 1 - XLS (CompactLight)

Teaser

Summary

Synchrotron light is electromagnetic radiation generated by charged particles that move at a speed near to the velocity of light on a curved path in accelerating machines called synchrotrons. The produced light, which is billion times more brilliant than light generated by conventional light sources, permits a large spectrum of applications in industry as well as basic and applied research in the fields of physics, chemistry, life sciences and medicine, environmental sciences etc. Currently, more than sixty synchrotron light sources are operational worldwide as giant microscopes for the study of matter.
In view of the huge utility and enormous utilisation of these machines, quantum jumps have been made in the last years in studying and implementing sources of even more intense electromagnetic radiation, called â€˜Free Electron Lasersâ€™ (FELs). These novel machines are based on linear accelerators (Linacs) for electrons followed by chains of undulators that force the high-speed electrons on wiggly trajectories, making them to emit light. The photon flux emitted by a FEL is several orders of magnitude higher than that produced by todayâ€™s synchrotron radiation sources and consists of light pulses that can be extremely short, with a duration of femtoseconds (fs, 10-15 sec) and wavelengths below an Ã…ngstrÃ¶m (Ã…, 10-10 m). This radiation, called hard X-rays, belongs to the high energy range of the X-ray spectrum. At the current state, these characteristics make the FEL the most powerful instrument for basic research on matter.
Given the continuously growing demand in terms of â€˜beamtimeâ€™ from the users, FEL sources are however not likewise distributed as synchrotrons, for technical reasons as well as for the huge investment and operation costs required.
CompactLight (XLS) is a H2020 Design Study funded by the European Union that started in January 2018 with a duration of three years. Launched by a group of 22 International Laboratories and two companies it aims at promoting the diffusion of FEL light sources at a global scale. The collaboration, coordinated by Elettra-Sincrotrone Trieste, brings together experts from the fields of electron sources, Linacs, and the structures required for the production of photons, to work on the â€˜Conceptual Designâ€™ of extremely compact FEL sources, with advanced performances and contained costs, in order to permit their diffusion also in contexts, where the financial resources for research are rather limited.

Work performed

The key concept of the project, which started in January 2018 with a duration of three years, is to use cutting-edge technologies for realizing each of the different components of a FEL facility, combining them into a single, highly innovative machine: (a) the most advanced electron sources and photo injectors, (b) very high-gradient normal conductive radio-frequency (RF) structures, operating at 12 GHz, developed at CERN in the context of the Compact Linear Collider (CLIC) study group, to increase the global efficiency of the machine and reduce the required length of the linac at a fixed energy of the electron beam, and (c) short period undulators of the last generation to obtain high energy photons with lower electron energies as compared to present-day machines.
Large progress in defining the machine parameters and designing each single subsystem has been made by the partners in the first reporting period of the project. Options for a very compact beam injector in the S-, C- and X-band of frequencies have been investigated and discussed. The definition of a standardised rf unit for the X-band linac is progressing, a component that could even be used as a stand-alone element for smaller projects, i. e. a university-scale Compton source, or smaller FELs for special applications that can be constructed and operated with smaller budgets. New concept undulators like superconductive undulators and cryogenic permanent-magnet undulators, as well as exotic schemes, like microwave undulators have also been, and are still, under investigation.
The collaboration is considering the design of two FEL sources, Soft X-ray (SXR, at lower energies) and Hard X-ray (HXR, at higher energies) that cover the wavelength range from 5.0 nm to 0.08 nm (from 0.25 keV to 16.0 keV), with the possibility to use the two sources contemporarily at 100 Hz, and individually with HXR at 100 Hz and SRX up to a repetition frequency of 1 KHz.
Besides technical feasibility, the choices of the machine parameters are essentially driven by the expectations of the FEL user community concerning photon beam characteristics of future FEL sources and the vision of the consortium to providing a real cutting-edge facility with unique performance and opportunities. In order to explore the scientific usersâ€™ requests, the partners have established a dialogue with them through presentations and discussions at relevant conferences and workshops, the conduction of an XLS User Survey, and a User Meeting with participation of representatives of the community held in the end of November 2018.

Final results

The overall concept underlying the project is to bring together recent advances in the main technical FEL sub-systems, i.e. electron photo-injector, linac accelerating structures and undulators, to produce the design of a next-generation facility with significantly lower cost and size than existing facilities. This brings to the use of very low emittance and higher repetition-rate sources, high-gradient linacs, high-efficiency klystrons, improved diagnostics, advanced undulators, the whole facility is being simulated using the most advanced beam dynamics and optimization tools, allowing to design such a cutting-edge facility.
The project will deliver to the scientific community a conceptual design of a machine with unique performance parameters and beam characteristics. The report will also include cost analyses and other strategic documents that support the decision-making process for constructing new facilities, or upgrading existing ones, using CompactLight technologies. The project will also consider the complementary use of the technology for small infrastructures, that can be installed and operated at universities. Project data not affecting the potential exploitation of results by the partners will be made accessible as Open Data to facilitate the use of the technologies.
The major goal of CompactLight is to make the construction and operation of X-ray FELs feasible for smaller countries, regions and universities. This will support their wide-spread availability, reducing oversubscription of existing machines, and creating more and unique research opportunities for the scientific users. Given the large importance of FELs their wide dissemination will have an enormous impact on many different research fields, create access opportunities in more countries, and contribute significantly to European scientific and industrial competitiveness. An important aspect is also the coordinated flow of expertise from Europeâ€™s larger research institutions to the smaller ones with ambitions to engage in cutting-edge photon science.
Major technology areas benefitting from the project are (a) high brightness e-sources (b) rf production and beam acceleration, (c) high-precision diagnostics, (d) undulators and photon production, etc., each of them with large application potential that goes beyond CompactLight and with clear opportunities for industries.