The ID10 beamline of the SESAME (Synchrotron-light for Experimental Science and Applications in the Middle East) synchrotron light source in Jordan was inaugurated in June 2023 and is now open to scientific users. The beamline, which was designed and installed within the European Horizon 2020 project BEAmline for Tomography at SESAME (BEATS), provides full-field X-ray radiography and microtomography imaging with monochromatic or polychromatic X-rays up to photon energies of 100 keV. The photon source generated by a 2.9 T wavelength shifter with variable gap, and a double-multilayer monochromator system allow versatile application for experiments requiring either an X-ray beam with high intensity and flux, and/or a partially spatial coherent beam for phase-contrast applications. Sample manipulation and X-ray detection systems are designed to allow scanning samples with different size, weight and material, providing image voxel sizes from 13 µm down to 0.33 µm. A state-of-the-art computing infrastructure for data collection, three-dimensional (3D) image reconstruction and data analysis allows the visualization and exploration of results online within a few seconds from the completion of a scan. Insights from 3D X-ray imaging are key to the investigation of specimens from archaeology and cultural heritage, biology and health sciences, materials science and engineering, earth, environmental sciences and more. Microtomography scans and preliminary results obtained at the beamline demonstrate that the new beamline ID10-BEATS expands significantly the range of scientific applications that can be targeted at SESAME.

The broadband nature of IRSR, together with the superior flux and higher brilliance are the key points of IR beamline scientific programs in 3rd generation SR rings. However, it is also well-established that the extraction of IRSR radiation from a bending magnet in the next-generation Diffraction Limited Storage Rings is a chal-lenging task. The Elettra 3rd generation storage ring in Trieste (Italy) is implementing its upgrade program to Elettra 2.0 DLSR, the design of which offers the possibility of a suitable extraction port for IR light, with com-parable extraction angles with respect to the present SISSI beamline. In this contribution we will present the results of the preliminary simulations run in Synchrotron Radiation Workshop on the expected performances of SISSI in Elettra 2.0. Considering the spatial constrains and the magnetic layout, also introduced here, two options for the IRSR source will be considered and benchmarked with the current SISSI beamline.

The European Horizon 2020 project BEAmline for Tomography at SESAME (BEATS) has the objective to design, procure, construct and commission a beamline for hard X-ray full-field tomography at the SESAME synchrotron in Jordan. In this paper we present the raytracing simulations performed to quantify the performance and verify the optical design of the beamline. The specifications of a vertically-deflecting double multilayer monochromator are investigated compar-ing multilayer mirrors with different meridional slope error. The use of a pinhole in the beamline Front-End (FE) acting as a secondary source with enhanced spatial coherence is discussed for phase-contrast applications. We anticipate that the BEATS beamline will fulfill the needs of a heterogeneous community of users of X-ray tomography at SESAME.

BEATS is an international collaboration funded by EU under the Horizon 2020 program, aimed to design and construct a hard X-ray full-field tomography beamline to be installed at SESAME synchrotron in Jordan. In this paper we present the design of the photon source and of the front end that interfaces the beamline with the accelerator. The photon source will consist of an out-of-vacuum 3-pole wiggler with a peak field of 3 Tesla; the contract for its manufacturing has been awarded to Kyma. INSERTION DEVICE REQUIREMENTS BEATS is one of the new beamlines currently under construction at the 2.5 GeV synchrotron light facility SESAME in Jordan. The beamline will operate a hard X-ray micro tomography station allowing a wide range of applications, including high-resolution phase contrast tomography scans, rapid scans of dynamical phenomena at medium resolution, as well as low-dose applications (biomedical imaging and cultural heritage) [1]. From the point of view of the photon source, the main requirements were: (i) to shift the critical photon energy of the emitted X-ray spectrum considerably above the one for the existing storage ring (SR) dipoles (1.45 Tesla, Ec = 6 keV), (ii) to maximize the flux and brightness of the delivered photon beam, and (iii) to reduce as much as possible the SR modifications required in order to mitigate the impact of the source on the electron beam. At an initial stage several options for the source were considered: a) a 3 Tesla superbend (Ec = 12.5 keV) replacing one of the SR dipoles, b) a 3 Tesla, λw = 50 mm period, 2.5 m-long multipole wiggler (MPW), c) a 3 Tesla 3-pole wiggler (3PW), with a strong central pole and two satellite poles to compensate the field integral. All options were carefully analysed taking into account their impact on the accelerator at different levels: effect on the beam dynamics, required hardware modifications, associated services, etc. [2]. As a result of this investigation the 3PW option was finally selected. The superbend option was rejected due to the large accelerator adaptations that it would entail (modification of both the girder and the vacuum chamber together with the installation of two new quadrupoles), whilst the MPW option would most likely require a superconducting magnet, with the added complexity of the associated cryogenic system. Furthermore, a 3 Tesla 3PW can be realized using out-of-vacuum permanent magnet technology, and the resulting device can be easily fitted in one of SESAME’s short straight sections, with a minimal impact on the technical systems of the facility.

We report on the successful operation of a Free Electron Laser (FEL) in the Echo Enabled Harmonic Generation (EEHG) scheme at the FERMI facility at Sincrotrone Trieste. The experiment required a modification of the FEL-2 undulator line which, in normal operation, uses two stages of high-gain harmonic generation separated by a delay line. In addition to a new seed laser, the dispersion in the delay-line was increased, the second stage modulator changed and a new manipulator installed in the delay-line chicane hosting additional diagnostic components. With this modified setup we have demonstrated the first evidence of strong exponential gain in a free electron laser operated in EEHG mode at wavelengths as short as 5 nm.

Laser-slicing at a diffraction-limited storage ring light source in the soft X-ray region is investigated with theoretical and numerical modelling. It turns out that the slicing efficiency is favoured by the ultra-low beam emittance, and that slicing can be implemented without interference to the standard multi-bunch operation. Spatial and spectral separation of the sub-picosecond radiation pulse from a hundreds of picosecond-long background is achieved by virtue of 1:1 imaging of the radiation source. The spectral separation is enhanced when the radiator is a transverse gradient undulator. The proposed configuration applied to the Elettra 2.0 six-bend achromatic lattice envisages total slicing efficiency as high as 10-7, one order of magnitude larger than the demonstrated state-of-the-art, at the expense of pulse durations as long as 0.4 ps FWHM and average laser power as high as ∼40 W.

Echo-enabled harmonic generation free-electron lasers (EEHG FELs) are promising candidates to produce fully coherent soft x-ray pulses by virtue of efficient high-harmonic frequency up-conversion from ultraviolet lasers. The ultimate spectral limit of EEHG, however, remains unclear, because of the broadening and distortions induced in the output spectrum by residual broadband energy modulations in the electron beam. We present a mathematical description of the impact of incoherent (broadband) energy modulations on the bunching spectrum produced by the microbunching instability through both the accelerator and the EEHG line. The model is in agreement with a systematic experimental characterization of the FERMI EEHG FEL in the photon energy range 130-210 eV. We find that amplification of electron beam energy distortions primarily in the EEHG dispersive sections explains an observed reduction of the FEL spectral brightness proportional to the EEHG harmonic number. Local maxima of the FEL spectral brightness and of the spectral stability are found for a suitable balance of the dispersive sections' strength and the first seed laser pulse energy. Such characterization provides a benchmark for user experiments and future EEHG implementations designed to reach shorter wavelengths.

The FERMI FEL-2 undulator line, normally operated in the double stage high gain harmonic generation with the fresh bunch (HGHG-FB) has been temporarily modified to allow operating the FEL in the Echo Enabled Harmonic Generation (EEHG) scheme. An increase of the dispersion in the delay-line was required together with a replacement of the second stage modulator allowing the electron beam to resonantly interact with a second seed laser. Another critical component of the EEHG setup is a new manipulator installed in the delay-line chicane and hosting additional diagnostic components. In this work we describe in some detail these new components that allowed a successful demonstration of the EEHG beam modulation at harmonics as high as 10

FERMI is the seeded Free Electron Laser (FEL) user facility at Elettra laboratory in Trieste, operating in the VUV to soft X-rays spectral range. In order to extend the FEL spectral range to shorter wavelengths, a feasibility study for increasing the Linac energy from 1.5 GeV to 1.8 GeV is actually going on. The design of new S-band accelerating structures, intended to replace the present Backward Travelling Wave sections, is presented. Such design is tailored for high gradient operation, low breakdown rates and low wakefield contribution. In this paper, we will also present the first, short prototype that has been built in collaboration with Paul Scherrer Institute (PSI).

FERMI is the seeded Free Electron Laser (FEL) user facility at the Elettra laboratory in Trieste, operating in the VUV to EUV and soft X-rays spectral range; the radiation produced by the seeded FEL is characterized by wavelength stability, low temporal jitter and longitudinal coherence in the range 100-4 nm. During 2018 a dedicated experiment has shown the potential of the Echo Enabled Harmonic Generation (EEHG) scheme [1] to cover most of this spectral range with a single stage cascade [2]. Such a scheme, combined to an increment of the beam energy and of the accelerator performances, could extend the FERMI operating range toward the oxygen k-edge. With this perspective, we present the development plans under consideration for the next 3 to 5 years. These include an upgrade of the linac and of the existing FEL lines, consisting in the conversion of FEL-1 first, and FEL-2 successively, into EEHG seeded FELs.

FERMI has reached its nominal performance on both FEL lines, FEL-1 (12 eV to 62 eV) and FEL-2 (62 eV to 310 eV). After a brief overview of the activities with users, we will describe plans for LINAC, FEL and beamline upgrades for 2016-2018 and beyond. This includes EEHG schemes for FEL-2. INTRODUCTION FERMI is the seeded Free Electron Laser (FEL), operating in the VUV to soft X-rays range, located at the Elettra laboratory in Trieste, Italy [1]. FERMI is the only FEL user facility designed to operate in the seeded HGHG mode [2] and has successfully demonstrated operation from 100 nm down to 4 nm [3, 4]. The VUV to EUV FEL line, FEL-1, started operation with external users, i.e. selected by the FERMI Review Panel, in December 2012. Since then a period of actual commissioning of the source with users has been conducted, in a strong interaction between machine and laser team and the users. This resulted in proposing and implementing innovative solutions and schemes for pumpprobe experiments. A portion of the seed laser is delivered as optical laser pulse to the experimental stations for pump-probe experiments with extremely low jitter to the FEL pulse, less than 7 fs rms [5]. Several schemes to produce two colour, FEL-pump and FEL-probe, pulses have been implemented [6-9]; the most recent FEL scheme makes use of two seed laser beams of different wavelengths and of a split radiator section to generate two extreme ultraviolet pulses from distinct portions of the same electron bunch [10]. A parameter under observation during user’s beamtimes is of course the actual availability of the FEL compared to the scheduled time. The uptime has been always around 85% of the scheduled time and, thanks to some improvements on the machine systems, has lately attained 90%. FEL-2 is the second FEL line of FERMI. It uses a double stage cascade scheme and the fresh bunch technique. First lasing was observed in 2012 [4] and the performance was gradually improved [11], in parallel to FEL-1 operation, until it reached nominal performances in 2014 [1]. The FEL emission of FEL-2 is characterized by excellent spectral line shapes and the transverse profile of the FEL pulses is close to the TEM00 Gaussian mode. At wavelengths below 5 nm the FEL tuning turned out to be critical, with large shot-to-shot energy fluctuations and with the necessity of a seed energy in excess of 40 J. Based on the experience of the operation for users on FEL-1 and of the commissioning of FEL-2, and with the aim of increasing the uptime of the facility beyond the 90% mark, a number of upgrade actions have been activated in 2015 and are being planned for 2016-2018. These upgrades shall further improve the performance of FEL-1 in the various multicolour schemes and should allow on FEL-2 similar tuning possibilities as on FEL-1, along with improved stability and flexibility of operation. OPERATION FOR USERS FERMI has been in operation for 6528 hours during 2015; 3520 hours thereof, that is 54% of the total operation time, were dedicated to users with a clear increase compared to the 43% reached in 2014. The remaining time has been divided between machine commissioning (1312 hours equal to 20% of the total operation time; was 40% in 2014) and machine and beamlines tuning (1696 hours, equal to 26% of the total operation time; was 17% in 2014). The average FEL uptime for users in 2015 was equal to 88.0% of the scheduled FEL time, confirming the effectiveness of the constant effort in increasing the reliability of the machine. In fact, in 2014 the uptime was equal to 86.1% and in 2013 to 84.7%. In the last run of 2015, that lasted three months under continuous operation, a value of 91% was registered. A total of 27 Users’ beamtimes, 20 peer-reviewed and 7 in-house, were allocated on the three beamlines operated in 2015, namely Diffraction and Projection Imaging (DiProI, 12 experiments), Low Density Matter (LDM, 7 experiments) and Elastic Inelastic Scattering TIMEX ____________________________________________ † email address: alessandro.fabris@elettra.eu MOPOW015 Proceedings of IPAC2016, Busan, Korea ISBN 978-3-95450-147-2 744 C op yr ig ht © 20 16 C C -B Y3. 0 an d by th e re sp ec tiv e au th or s 02 Photon Sources and Electron Accelerators A06 Free Electron Lasers (EIS-TIMEX, 6 experiments). In-house beamtimes in 2015 also included commissioning of the EIS-TIMER experimental station, which started in July [12] and continued in November, when the first evidence of a transient-grating signal was observed from a BaF2 sample. Also the commissioning of the TeraFERMI beamline, that collects the THz radiation (ultrashort pulses in the 0.1-15 THz range) naturally emitted by the electron beam already spent by the FEL undulators, has started in December 2015 and the first THz photons have been observed. The sixth beamline at FERMI is MagneDyn, dedicated to the exploration of the ultimate limits of magneto-dynamic processes in conventional and advanced magnetic materials. This beamline is still under construction, with the commissioning expected to begin at the end of 2016. After five calls the number of the submitted proposals by users requiring beamtime for experiments at FERMI is still steadily increasing. In the last call for experiments, at the beginning of February, 72 proposals were submitted, 21 of them are experiments using FEL-2. The estimated oversubscription rate is about 3.4. UPGRADE RESULTS 2016 The first upgrade program started between 2014 and 2015, focused mainly on the LINAC and on FEL-2. The results collected in a dedicated commissioning period scheduled at the beginning of 2016 are discussed in the following sections. LINAC FERMI is driven by a 200 meter long S-band LINAC. In the injector region, two 3-meter long forward traveling wave accelerating structures, coming from the old Elettra injector, were installed. In order to improve the electron beam quality, it was decided to replace the first two existing structures with two dual-feed accelerating structures [13]. The structures were manufactured by Research Instruments GmbH and delivered to Elettra in July 2015. Figure 1: The new accelerating structures in the injector. After the high power testing in the FERMI cavity test facility, in January 2016 the structures were installed, on schedule, in the injector region, as shown in Fig. 1. The old structures were consequently moved into the high energy region of the LINAC to further increase the final energy by approximately 90 MeV. In February 2016 normalized emittances of 0.7 and 0.9 mm mrad in the horizontal and vertical plane, respectively, were measured in the 100 MeV diagnostic section. These values at 700 pC are 10-15% smaller than the previous ones. Peak LINAC energies as high as 1629 MeV were measured. The maximum operating energy, with compressed and linearized electron beam phase space, at 700 A of nominal current, is about 1550 MeV (see Fig. 2). Figure 2: Maximum LINAC operating energy. FEL-2 In 2014 the design parameters of FEL-2 were demonstrated down to the lower end of the wavelength range, 4 nm. However, it appeared evident that upgrades were needed to improve the stability and flexibility of FEL-2, and to achieve a frequency tunability similar to the one available on FEL-1 (OPA operation). The first of these upgrades addressed the LINAC energy, as described in the previous section. The second upgrade, specific to FEL-2, consists in the installation of a second regenerative amplifier. It produces a shorter seed pulse (infrared pulse duration less than 40 fs, 60-70 fs in the UV) that allows for better filling of the longitudinal phase space in fresh bunch mode. The laser also permits a wavelength tunability in the UV (+/-2%) allowing a limited FEL wavelength tuning with the third harmonic generation setup. As well a second OPA laser system was installed, so that double pulse seeding is possible on FEL-1 with two fully tunable sources. Another important upgrade of FEL-2 consists in the installation of a third Elliptically Polarized Undulator (EPU) in the radiator of the first HGHG stage of FEL-2, completing the design layout of this FEL line, shown in Fig. 3. Figure 3: FEL-2 with the new installed EPU. Proceedings of IPAC2016, Busan, Korea MOPOW015 02 Photon Sources and Electron Accelerators A06 Free Electron Lasers ISBN 978-3-95450-147-2 745 C op yr ig ht © 20 16 C C -B Y3. 0 an d by th e re sp ec tiv e au th or s The additional EPU reduces the seed energy required for operation in the shorter wavelength range, providing the possibility to operate with OPA laser system in a longer wavelength range. The EPU was built by Kyma srl with the same parameters of the two already existing ones: 55.2 mm period length, 42 periods, 10 mm gap. In March 2016, after the upgrades, FEL-2 reached unprecedented shot to shot stability, below 6% rms at 4.2 nm, as shown in Fig. 4, and average intensity greater than 15 J/pulse. The energy requirement from the seed laser could be reduced to less than 20 J. The new undulator configuration also offers the flexibility to operate efficiently with different harmonic conversion factors, as 16x4 which is almost equivalent to 13x5 used in the past. Figure 4: FEL-2 pulse by pulse intensity at 4.2 nm. Reasonable energy per pulse was measured down to 3.8 nm. Radiation spectra could be measured in single shot even at harmonic 3.1 nm, as shown in Fig. 5. Figure 5: Single shot spectrum at harmonic 17x5=85. The plots in the inset of Fig. 5 represent spectra from multiple shots during the same sequence. The green line is the projection of the single shot CCD acquisition displayed in the figure. The vertical axis represents the unfocused vertical distribution of the FEL pulse. PLANS FOR THE NEAR FUTURE The upgrade plans for 2017-2018 at FERMI foresee exploring the possibility of replacing the aging S-band Backward Traveling Wave structures (BTWs) of the LINAC and to implement the Echo Enabled Harmonic Generation scheme (EEHG) on FE

FERMI is the seeded Free Electron Laser (FEL) user facility at the Elettra laboratory in Trieste, operating in the VUV to EUV and soft X-rays spectral range; the radiation produced by the seeded FEL is characterized by wavelength stability, low temporal jitter and longitudinal coherence in the range 100-4 nm. During 2018 a dedicated experiment has shown the potential of the Echo Enabled Harmonic Generation (EEHG) scheme [1] to cover most of this spectral range with a single stage cascade [2]. Such a scheme, combined to an increment of the beam energy and of the accelerator performances, could extend the FERMI operating range toward the oxygen k-edge. With this perspective, we present the development plans under consideration for the next 3 to 5 years. These include an upgrade of the linac and of the existing FEL lines, consisting in the conversion of FEL-1 first, and FEL-2 successively, into EEHG seeded FELs.

Chirped pulse amplification in optical lasers is a revolutionary technique, which allows the generation of extremely powerful femtosecond pulses in the infrared and visible spectral ranges. Such pulses are nowadays an indispensable tool for a myriad of applications, both in fundamental and applied research. In recent years, a strong need emerged for light sources producing ultra-short and intense laser-like X-ray pulses, to be used for experiments in a variety of disciplines, ranging from physics and chemistry to biology and material sciences. This demand was satisfied by the advent of short-wavelength free-electron lasers. However, for any given free-electron laser setup, a limit presently exists in the generation of ultra-short pulses carrying substantial energy. Here we present the experimental implementation of chirped pulse amplification on a seeded free-electron laser in the extreme-ultraviolet, paving the way to the generation of fully coherent sub-femtosecond gigawatt pulses in the water window (2.3-4.4 nm).

FERMI is the seeded FEL user facility in Trieste, Italy, producing photons from the VUV to the soft X-rays with a high degree of coherence and spectral stability. Both FEL lines, FEL-1 and FEL-2, are now available for users, down to the shortest wavelength of 4 nm. We will report on the completion of the commissioning of the high energy FEL line, FEL-2, and on the operational experience for users, in particular those requiring specific FEL configurations, like two-colour experiments. We will also give a perspective on the improvements and upgrades which have been triggered by our experience and are aiming to maintain as well as to constantly improve the performance of the facility for our user community.