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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., Proceedings of the 39th Free Electron Laser Conference, FEL2019, Hamburg, Germany

Elettra Sincrotrone Trieste Research Center (Elettra) is one the Italian Institutions, together with Istituto Nazionale di Fisica Nucleare (INFN) and Consiglio Nazionale delle Ricerche (CNR), committed to the realization of the Italian in-kind contributions for the European Spallation Source. Elettra contributions are concentrated on the proton accelerator and more specifically they concern the construction of the conventional iron-dominated electro-magnets and related power converters to be installed in the superconducting part of the linac and in the High Energy Beam Transport (HEBT), the RF power stations for the superconducting spoke cavity linac section and the wire scanner acquisition system for the beam diagnostics. This paper provides a description of the contributions and an overview of the status of the construction activities., Proceedings of the 10th Int. Particle Accelerator Conf., IPAC2019, Melbourne, Australia

Elettra Sincrotrone Trieste, a specialized research centre generating high quality synchrotron radiation, has been in operation since 1993 and was revised in 2009. Recently, Elettra has been funded for a complete renewal of the storage ring. For the new machine, it is planned to employ state of the art converters, mostly of which will be designed in-house. For this purpose, it has been decided to evaluate the performance of a storage-less resonant converter, pro-posed by Dr. Slobodan Ćuk, which is a step down DC/DC converter consisting of four switches, one resonant capac-itor and two resonant inductors. For this purpose, the voltage conversion ratio of the converter has been de-rived. The topology was confirmed with simulation and a PCB layout has been designed, which is still to be tested., Proceedings of the 10th Int. Particle Accelerator Conf., IPAC2019, Melbourne, Australia

The FERMI FEL-2 undulator line, normally operated in the double stage high gain harmonic generation with the fresh bunch (HGHG-FB) has been temporary 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 at harmonics as high as 101., Proceedings of the 10th Int. Particle Accelerator Conf., IPAC2019, Melbourne, Australia

In the frame of the Italian In-Kind collaboration for the construction of the European Spallation Source (ESS), Elettra Sincrotrone Trieste research center is in charge, among all, of the provision of the power converters for the warm magnets of the superconducting part of the linear accelerator and of the proton beam transport line. The procurement process is running for all types of power converters. The first components have been delivered to ESS already in March 2018, while the Dipole and Quadrupole power converters are under construction. The first batches have been factory tested and shipped to Lund. The corrector power converters have been manufactured and are currently tested and calibrated at Elettra before their delivery to ESS., Proceedings of the 10th Int. Particle Accelerator Conf., IPAC2019, Melbourne, Australia

26 equivalent 400 kW Radio Frequency Power Station (RFPS) units will be provided by Elettra as part of the Italian in kind contribution to ESS. They will be installed in the LINAC "Spoke Section". Each RFPS will power a single superconducting spoke cavity in pulsed operation at 352.21 MHz. The RFPS is a complete system that operates unmanned, based on a combination of solid state and tetrode amplification’s stages. The tender specification, the RFPS main features and requested performances are reported here., Proceedings of the 10th Int. Particle Accelerator Conf., IPAC2019, Melbourne, Australia

The operational status of the Italian 2.4/2.0 GeV third generation light source Elettra is presented together with an account of some present upgrades and plans for the near future., Proceedings of the 8th Int. Particle Accelerator Conf., IPAC2017, Copenhagen, Denmark

In the framework of the Italian In-Kind Contribution (IKC) to the construction of the European Spallation Source (ESS), Elettra Sincrotrone Trieste is in charge of providing some key equipment for the accelerator. Among them, there are the magnets and the associated power converters for the Linac Warm Units (LWU), the High Energy Beam Transport (HEBT) dogleg, the Dump Line (DmpL) and the Accelerator to Target (A2T) sections of the neutron source. Magnets and their power converters are complementary parts of common systems. Their design cannot be totally separated, requiring iterations for an optimal solution that should include also power cable standardization. This work will describe the power converters' solutions adopted for the magnets of the above-mentioned sections. They comprise 4-Quadrant power converters for the correctors, compact DC power converters for the small quadrupole magnets and more powerful DC power converters for the dipole and large quadrupole magnets., Proceedings of the 8th Int. Particle Accelerator Conf., IPAC2017, Copenhagen, Denmark

Ageing of devices and components phasing-out, as well as the increasing maintenance costs, affect particle accelerators similarly to any industrial plant. A careful maintenance plan can cope with these problems in the medium-term, but then a complete update of the oldest parts is required. The most recent technologies available on the market together with a modular and open design approach are the basis of an upgrade program aimed at replacing the existing controllers of the Elettra storage ring magnet power supplies. The design considerations, the constraints and the first results are reported., Proceedings of the 5th Int. Particle Accelerator Conf., IPAC2014, Dresden, Germany

A 3.5 Tesla 64 mm period superconducting wiggler (SCW) was constructed by the Russian Budker Institute of Novosibirsk (BINP) and installed in the Elettra storage ring as a photon source for the second X-ray diffraction beamline in November 2002, but never used due to the lack of the funding required for the beamline construction. About three years ago, the beamline construction was finally funded together with the refurbishment of the SCW. This upgrade, that was necessary in order to make the SCW operations compatible with the top up mode of the storage ring aimed in a drastic reduction of the liquid helium consumption by means of replacing the cryostat with a new version. At the same time the upgrade aimed as well to improve the reliability of the cryostat, to update the control system and to verify the magnetic field performance after a very long time of inactivity. In this paper we present and discuss the performances of the SCW following its refurbishment carried out by BINP team and its re-commissioning in the Elettra storage ring., Proceedings of the 5th Int. Particle Accelerator Conf., IPAC2014, Dresden, Germany

Nature photonics 13(8), 555 - 561 (2019). doi:10.1038/s41566-019-0427-1, X-ray free-electron lasers (FELs), which amplify light emitted by a relativistic electron beam, are extending nonlinear optical techniquesto shorter wavelengths, adding element specificity by exciting and probing electronic transitions from core levels. Thesetechniques would benefit tremendously from having a stable FEL source, generating spectrally pure and wavelength-tunable pulses.We show that such requirements can be met by operating the FEL in the so-called echo-enabled harmonic generation (EEHG) configuration.Here, two external conventional lasers are used to precisely tailor the longitudinal phase space of the electron beambefore emission of X-rays. We demonstrate high-gain EEHG lasing producing stable, intense, nearly fully coherent pulses at wavelengthsas short as 5.9 nm (~211 eV) at the FERMI FEL user facility. Low sensitivity to electron-beam imperfections and observationof stable, narrow-band, coherent emission down to 2.6 nm (~474 eV) make the technique a prime candidate for generatinglaser-like pulses in the X-ray spectral region, opening the door to multidimensional coherent spectroscopies at short wavelengths., Published by Nature Publ. Group, London [u.a.]

In hard X-ray applications that require high detection efficiency and short response times, such as synchrotron radiation-based Mössbauer absorption spectroscopy and time-resolved fluorescence or photon beam position monitoring, III–V-compound semiconductors, and dedicated alloys offer some advantages over the Si-based technologies traditionally used in solid-state photodetectors. Amongst them, gallium arsenide (GaAs) is one of the most valuable materials thanks to its unique characteristics. At the same time, implementing charge-multiplication mechanisms within the sensor may become of critical importance in cases where the photogenerated signal needs an intrinsic amplification before being acquired by the front-end electronics, such as in the case of a very weak photon flux or when single-photon detection is required. Some GaAs-based avalanche photodiodes (APDs) were grown by a molecular beam epitaxy to fulfill these needs; by means of band gap engineering, we realised devices with separate absorption and multiplication region(s) (SAM), the latter featuring a so-called staircase structure to reduce the multiplication noise. This work reports on the experimental characterisations of gain, noise, and charge collection efficiencies of three series of GaAs APDs featuring different thicknesses of the absorption regions. These devices have been developed to investigate the role of such thicknesses and the presence of traps or defects at the metal–semiconductor interfaces responsible for charge loss, in order to lay the groundwork for the future development of very thick GaAs devices (thicker than 100 μm) for hard X-rays. Several measurements were carried out on such devices with both lasers and synchrotron light sources, inducing photon absorption with X-ray microbeams at variable and controlled depths. In this way, we verified both the role of the thickness of the absorption region in the collection efficiency and the possibility of using the APDs without reaching the punch-through voltage, thus preventing the noise induced by charge multiplication in the absorption region. These devices, with thicknesses suitable for soft X-ray detection, have also shown good characteristics in terms of internal amplification and reduction of multiplication noise, in line with numerical simulations.