1. Summary of XFEL uses for CALIFES Erik Adli (University of Oslo, Norway) 2015-03-12

2. Background The 200 MeV CALIFES electron beam line in CTF3/CLEX is currently scheduled to shut down after 2016, together with the rest of CTF3. The case for CALIFES operation beyond 2016 is currently being investigated. We are in the process of summarizing this interest and which institutes are interested/proponents of the proposal. For this iteration we have generated a compact document, not meant to go in technical details, aimed for internal use at CERN (management, getting CERN groups on board). A two-page “executive summary” will also be prepared The XFEL case and the XbFEL collaboration is an important part of the case for CALIFES I will show what we have written about XFEL The text is based on the presentations and the discussion we have had up to now, especially during the CLIC workshop 2015 From introduction “….The last couple of years have seen an increased interest in continuing the operation of CALIFES beyond 2016. A number of external institutes and laboratories, in addition to projects and groups at CERN, have expressed their interest in using CALIFES as an electron linac test facility after the shutdown of the drive beam complex. Such expressions of interest are summarized in Chapter 3. CALIFES is a small part of CTF3 and is significantly easier to operate than the drive beam generation complex. The resources required to operate this machine beyond 2016 are only a small fraction of what is required to operate the whole facility. “

3. “There is rapidly growing worldwide interest in XFELs and a parallel trend to using higher accelerating frequencies for more compact linacs. An international collaboration consisting of 12 institutes worldwide (10 from Europe) is actively studying the design of a compact and cost-effective Free Electron Laser based on acceleration using CLIC X-band technology (the “XbFEL” collaboration). Component tests and technology demonstrations are an important part of this study. Accessibility of accelerator facilities for such studies is extremely limited in FEL user facilities. In the UK, the CLARA test-facility is proposed for FEL experiments [CLARA, http://www.stfc.ac.uk/2905.aspx], focusing on a rich photon production program. However, at CLARA the possibilities to perform electron beam and RF experiments will be limited as well. The critical beam parameter for a FEL is the peak current, and a number of X-band components need to be studied for the XbFEL project, including phase-space linearizers, transverse deflecting cavities (for bunch length diagnostics and RF spreaders) and wakefield monitors. CALIFES would be the only facility in Europe where a significant amount of time could be dedicated to such tests. For the XbFEL collaboration it is also of great interest to test novel bunch compression schemes and advanced beam physics including purely magnetic compression systems. ” XFEL text 1

4. “Interest from PSI The SwissFEL is currently under construction at PSI, Switzerland with the start of operations planned for 2017. Accessibility of the facility for new developments will be extremely limited once the SwissFEL is running as a user facility. It is therefore of interest for the SwissFEL project to have access to an electron beam for hardware development studies beyond 2016, including short bunch studies, X-band RF deflectors and wakefield monitors. In many cases the interests are coinciding with those of the XbFEL collaboration. The SwissFEL project could also possibly contribute hardware to CALIFES test facility, including the magnetic chicane for bunch compression currently installed at the SwissFEL test facility. This chicane could be used for CALIFES bunch compression in general, in addition to tests of advanced bunch compression schemes for FELs. “ XFEL text 2

5. “Interest from Elettra-Sincrotrone Trieste The Fermi FEL at Trieste has been operating since 2010. For upgrades of the machine, many advanced ideas for electron beam manipulation have been studied, including arcs with CSR compensation and experiments to study the microbunching instability. As for the SwissFEL, the accessibility of the production machine for beam dynamics R&D is very limited, and CALIFES could provide an excellent test bed for electron beam manipulation schemes. Beam requirements The CALIFES facility as it is provides the beam specifications to perform most of the X-band component tests described above. The Xbox 1 RF source may power X-band linearizers and deflecting cavities. The possibility of using the SwissFEL magnetic chicane for CALIFES is very interesting both for PSI and for the CALIFES test facility.” XFEL text 3

6. Institutes listed so far Institutes expressing the interest : L. Giannessi, M. Kiskinova, C. Masciovecchio, A. Santelli, Elettra-Sincrotrone Trieste A. Latina, D. Schulte, S. Stapnes, W. Wuensch, CERN, Geneva C. Bocchetta, Jagiellonian University, Krakow J. Clarke, Daresbury Laboratory Cockcroft Institute, Daresbury W. Fang, Shangai Institute of Applied Physics, Shanghai X.J.A. Janssen VDL ETG T&D B.V., Eindhoven E. Adli, J. Pfingstner, University of Oslo E. N. Gazis, National Technical University of Athens M. Jacewicz, R. Ruber, Uppsala University, Uppsala M. J. Boland, Australian Synchrotron, Clayton A. Aksoy, Ö. Yavaş, Institute of Accelerator Technologies, Ankara, Turkey. G. Burt, Lancaster University, Lancaster M. Dehler, PSI