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X-ray free-electron lasers (FELs), which amplify light emitted by a relativistic electron beam, are extending nonlinear optical techniques to shorter wavelengths, adding element specificity by exciting and probing electronic transitions from core levels. These techniques 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 beam before emission of X-rays. We demonstrate high-gain EEHG lasing producing stable, intense, nearly fully coherent pulses at wavelengths as short as 5.9 nm (~211 eV) at the FERMI FEL user facility. Low sensitivity to electron-beam imperfections and observation of stable, narrow-band, coherent emission down to 2.6 nm (~474 eV) make the technique a prime candidate for generating laser-like pulses in the X-ray spectral region, opening the door to multidimensional coherent spectroscopies at short wavelengths.Echo-enabled harmonic generation in a free-electron laser enables 45th harmonic pulses from a 264 nm wavelength seed, yielding 5.9 nm wavelength coherent output.

The two single-pass, externally seeded free-electron lasers (FELs) of the FERMI user facility are designed around Apple-II-type undulators that can operate at arbitrary polarization in the vacuum ultraviolet-to-soft x-ray spectral range. Furthermore, within each FEL tuning range, any output wavelength and polarization can be set in less than a minute of routine operations. We report the first demonstration of the full output polarization capabilities of FERMI FEL-1 in a campaign of experiments where the wavelength and nominal polarization are set to a series of representative values, and the polarization of the emitted intense pulses is thoroughly characterized by three independent instruments and methods, expressly developed for the task. The measured radiation polarization is consistently >90% and is not significantly spoiled by the transport optics; differing, relative transport losses for horizontal and vertical polarization become more prominent at longer wavelengths and lead to a non-negligible ellipticity for an originally circularly polarized state. The results from the different polarimeter setups validate each other, allow a cross-calibration of the instruments, and constitute a benchmark for user experiments.

This work introduces a novel setup for computed tomography of heavy and bulky specimens at the SYRMEP beamline of the Italian synchrotron Elettra. All the key features of the setup are described and the first application to off‐center computed tomography scanning of a human chest phantom (approximately 45 kg) as well as the first results for vertical helical acquisitions are discussed. This work introduces a novel setup to scan heavy and bulky specimen at the SYRMEP beamline, which will be the basis for future phase contrast lung computed tomography imaging in patients.

Free-electron lasers (FELs) are the most advanced class of light-sources, by virtue of their unique capability to lase high-brightness pulses characterized by wavelengths spanning the extreme-ultraviolet, the soft and hard X-ray spectral domains, as well as by temporal lengths lying in the femtosecond (fs) timescale. The next step to push the current standards in ultrafast X-ray science is strongly linked to the possibility of engineering and exploiting time-resolved experiments exclusively for FELs pulses, ideally having different colors tunable at specific electronic resonance of the chemical elements. At the seeded FERMI FEL (Trieste, Italy) this goal is committed to the optical device known as AC/DC, which stands for the auto correlator/delay creator. AC/DC is designed to double the incoming FEL pulse splitting the photon beam by inserting a grazing incidence flat mirror, thus preserving the spectral and temporal properties, and further delaying one of these two pulses in time. It can independently tune the FEL pulses fluence on the two optical paths by means of solid-state filters, too. Here, we present a detailed description about this optical device. Strong emphasis is dedicated to the AC/DC opto-mechanical design and to the laser-based feedback systems implemented to compensate for any mismatch affecting the FEL optical trajectory, ascribable to both mechanical imperfections and paraxial errors rising during a temporal delay scan.

The current CoViD-19 pandemic threatens both physical and psychological well-being. According to the bio-psycho-social model, Units of Clinical Psychology of the Hospitals in Lombardy (Italy) reacted to this risk, offering diversified interventions, described in the present contribution. The medical staff operated on the front line during the emergency: psychologists addressed their needs through individual clinical work, sessions of decompression and debriefing. At the same time, Units of Clinical Psychology supported the hospitalized positive patients by conducting psychological consultations, either on the ward or through devices. Moreover, some hospitals activated helplines to address the needs of the population and family members, who were particularly vulnerable during the relative's illness and after the mourning.

La pandemia attuale di CoViD-19 costituisce un’ingente minaccia sia per la salute fisica sia per il benessere psicologico. Considerando il processo di cura in un’ottica bio-psico-sociale, le Unità Operative di Psicologia (UOPSI) delle Aziende Socio-Sanitarie Territoriali (ASST) lombarde hanno risposto all’emergenza proponendo diversificati interventi psicologici, presentati in questo studio. Particolare attenzione è stata rivolta allo staff medico, operante in prima linea durante questa emergenza: gli psicologi clinici delle ASST hanno istituito uno spazio di supporto individuale e hanno offerto agli operatori la possibilità di accedere agli incontri di decompressione e debriefing. Parallelamente, le UOPSI hanno supportato i pazienti positivi ricoverati, effettuando interventi di consultazione, condotti in reparto o tramite device. Infine, in alcune ASST sono state attivate delle helpline, affinché potessero essere accolte le domande della popolazione generale e dei familiari dei pazienti, particolarmente vulnerabili durante la malattia dei loro cari e soprattutto dopo il lutto.