Search

Abstract X-ray free-electron lasers (FELs) are state-of-the-art scientific tools capable to study matter on the scale of atomic processes. Since the initial operation of X-ray FELs more than a decade ago, several facilities with upgraded performance have been put in operation. Here we present the first lasing results of Athos, the soft X-ray FEL beamline of SwissFEL at the Paul Scherrer Institute in Switzerland. Athos features an undulator layout based on short APPLE-X modules providing full polarisation control, interleaved with small magnetic chicanes. This versatile configuration allows for many operational modes, giving control over many FEL properties. We show, for example, a 35% reduction of the required undulator length to achieve FEL saturation with respect to standard undulator configurations. We also demonstrate the generation of more powerful pulses than the ones obtained in typical undulators. Athos represents a fundamental step forward in the design of FEL facilities, creating opportunities in FEL-based sciences.

We demonstrate the generation of coherent soft x-ray free-electron laser (FEL) pulses with a duration below 1 fs using nonlinear compression with a low-charge electron beam (10 pC). The approach is simple, and it does not require any special hardware, so it can be readily implemented at any x-ray FEL facility. We present temporal and spectral diagnostics confirming the production of single-spike sub-femtosecond pulses for photon energies of 642 and 1111 eV. Our work will be important for ultrafast FEL applications requiring soft x-rays.

A novel registered practical nurse-led video conferencing approach using PIECESTM for team-based care planning was developed to engage family/care partners in the care of older adults. The objectives were to: (a) explore the experiences of older adults and family/care partners in collaborating in implementation science research in long-term care (LTC); (b) identify facilitators and barriers to engaging older adults and family/care partners in implementation science research; and (c) share recommendations to support the engagement of older adults and family/care partners in research. A qualitative descriptive design was used. Two older adults and two family/care partners from two Canadian LTC homes were involved in the research. Data, comprised of interviews with older adults and family/care partners, and notes from research team meetings, were analyzed using thematic analysis. Older adults and family/care partners perceived they made valuable contributions to the research project. They expressed beliefs that care delivery required improvements for older adults with responsive behaviours in LTC, which served as motivation to participate in the research project. Facilitating factors included the support of familiar LTC staff for older adults to engage in research activities and understanding the value of PIECES. A barrier to engagement for older adults was research terminology and processes described during team meetings. This research highlighted taken-for-granted factors in a collaborative research endeavour with older adults and family/care partners. One-on-one interaction, follow-up 'reporting' and presence of familiar LTC staff are needed to support meaningful engagement of older adults and family/care partners in research. Experience Framework This article is associated with the Innovation & Technology lens of The Beryl Institute Experience Framework (https://theberylinstitute.org/experience-framework/). Access other PXJ articles related to this lens. Access other resources related to this lens.

Longitudinal electron-beam diagnostics play a critical role in the operation and control of x-ray free-electron lasers, which rely on parameters such as the current profile, the longitudinal phase space, or the slice emittance of the particle distribution. On the one hand, the femtosecond-scale electron bunches produced at these facilities impose stringent requirements on the resolution achievable with the diagnostics. On the other, research and development of novel accelerator technologies such as beam-driven plasma-wakefield accelerators (PWFA) demand unprecedented capabilities to resolve the centroid offsets in the full transverse plane along the longitudinal bunch coordinate. We present the beam-based commissioning of an advanced X-band transverse-deflection rf structure (TDS) system with the new feature of providing variable polarization of the deflecting force: the PolariX-TDS. By means of a comprehensive campaign of measurements conducted with the prototype, key parameters of the rf performance of the system are validated and a phase-space characterization of an electron bunch is accomplished with a time resolution of 3.3 fs. Furthermore, an analysis of second-order effects induced on the bunch from its passage through the PolariX-TDS is presented.

The intrinsic energy spread of electron beams needs to be measured to characterize and optimize high-brightness electron beam sources such as those driving x-ray free-electron lasers (FELs). We demonstrate the use of the optical klystron effect as a precise and high-resolution method to measure the electron beam energy spread. The optical klystron setup consists of undulator modules and magnetic chicanes placed between them. The energy spread is found by measuring the radiation power produced in the undulators as a function of the chicanes’ strengths. High resolution and simplicity are the advantages of this approach, in contrast to the standard method, which measures the longitudinal phase space of the electron beam with a transverse deflector. The demonstration was performed at Athos, the soft x-ray FEL beamline of SwissFEL, for which we measured energy spreads below 1 MeV at a central beam energy of 3.4 GeV. We have verified the consistency of the method for different parameters (radiation wavelengths, undulator polarization configurations, and electron bunch durations) and we have benchmarked it against the standard measurement approach using a transverse deflector. Our results confirm the optical klystron as a valid approach to measure the electron beam energy spread. The method can be especially useful to reconstruct low energy spread values, where the conventional approach may be resolution limited, such as in ultra high-brightness radiofrequency photoinjectors or plasma sources, or when transverse deflectors are not available.

The PSI Positron Production (P^{3} or P-cubed) experiment is a e^{+} source and capture system with the potential to increase by an order of magnitude the state-of-the-art e^{+} yield normalized to the drive linac energy, a highly desirable goal for future colliders. The experiment is framed in the FCC-ee injector study and will be hosted at SwissFEL, located at the Paul Scherrer Institute in Switzerland. This paper presents the P^{3} project at an advanced stage, with an emphasis on a capture system featuring a novel e^{+} matching device based on high-temperature superconducting solenoids, followed by two large aperture rf cavities surrounded by normal-conducting solenoids. The diagnostics design is also introduced, including monitors of charge, energy spectrum, and bunch-by-bunch longitudinal profile simultaneously for secondary e^{+} and e^{-}. The last chapter of the text overviews the currently ongoing installation at SwissFEL, including the beam transfer line, rf network, radiation protection, and other relevant activities toward the operation with e^{+} in the coming years.

The first generation of S-band injectors for free-electron lasers has illustrated high reliability and performance by driving the latest generation of high brightness machines. However, the ultimate electron beam brightness of these devices is limited by the electric field that they can achieve on the cathode. With the aim of a higher beam brightness at SwissFEL, this paper presents the design of a C-band traveling-wave (TW) radio-frequency photogun that aims to offer the possibility to move to a cathode gradient up to 200 MV/m. This increased gradient comes from the ability to operate with rf pulse lengths approximately an order of magnitude shorter than the current state-of-the-art room-temperature S-band standing-wave rf photoguns. With this high cathode gradient, this novel gun is able to produce an electron bunch whose 5D beam brightness is 5 times greater than the current SwissFEL photogun. Furthermore, the low power dissipation within the photogun, resulting from the short rf pulse length and TW philosophy, opens up the opportunity for rf pulse repetition rates up to 1 kHz.

BackgroundWorldwide, the COVID-19 pandemic has resulted in profound loss of life among older adults living in long-term care (LTC) homes. As a pandemic response, LTC homes enforced infection control processes, including isolating older adults in their rooms, canceling therapeutic programs, and restricting family member visits. Social isolation negatively impacts older adults in LTC, which may result in increased rates of anxiety, depression, physical and cognitive decline, disorientation, fear, apathy, and premature death. Isolation of older adults can also cause an increase in responsive behaviors (eg, yelling, hitting, calling out) to express frustration, fear, restricted movement, and boredom. To respond to the challenges in LTC and support frontline staff, older adults, and family members, a novel registered practical nurse (RPN)-led delivery of the PIECES approach for addressing responsive behaviors among older adults with dementia using virtual training/mentoring was implemented in Canadian LTC homes. PIECES employs a person- and family/care partner–centered collaborative team-based approach to provide education and capacity-building for nurses; engages families as active participants in care; and embeds evidence-informed practices to provide person- and family-centered care to older adults with complex needs, including dementia. ObjectiveThe aim of this study was to describe the experiences of LTC staff, family/care partners, and older adult research partners with implementation of a novel RPN-led virtual adaptation of the PIECES care-planning approach for responsive behaviors in two Canadian LTC homes during the COVID-19 pandemic. MethodsUsing a qualitative descriptive design, two focus groups were held with three to four staff members (eg, RPNs, managers) per LTC home in Ontario. A third focus group was held with three PIECES mentors. Individual semistructured interviews were conducted with RPN champions, family/care partners, and older adult research partners. Research team meeting notes provided an additional source of data. Content analysis was performed. ResultsA total of 22 participants took part in a focus group (n=11) or an in-depth individual interview (n=11). Participant experiences suggest that implementation of RPN-led virtual PIECES fostered individualized care, included family as partners in care, increased interdisciplinary collaboration, and improved staff practices. However, virtual PIECES, as delivered, lacked opportunities for family member feedback on older adult outcomes. Implementation facilitators included the provision of mentorship and leadership at all levels of implementation and suitable technological infrastructure. Barriers were related to availability and use of virtual communication technology (family members) and older adults became upset due to lack of comprehension during virtual care conferences. ConclusionsThese findings offer promising support to adopting virtual PIECES, a team approach to gather valuable family input and engagement to address residents’ unmet needs and responsive behaviors in LTC. Future research should investigate a hybridized communication format to foster sustainable person- and family-centered care-planning practices to include active collaboration of families in individualized care plans.

Abstract The PolariX TDS (Polarizable X-Band Transverse Deflection Structure) is an innovative TDS-design operating in the X-band frequency-range. The design gives full control of the streaking plane, which can be tuned in order to characterize the projections of the beam distribution onto arbitrary transverse axes. This novel feature opens up new opportunities for detailed characterization of the electron beam. In this paper we present first measurements of the Polarix TDS at the FLASHForward beamline at DESY, including three-dimensional reconstruction of the charge-density distribution of the bunch and slice emittance measurements in both transverse directions. The experimental results open the path toward novel and more extensive beam characterization in the direction of multi-dimensional-beam-phase-space reconstruction.

SwissFEL has a unique capability, among the normal conducting linac-based light sources, to simultaneously serve two separate undulator lines (Aramis and Athos) up to the machine repetition rate of 100 Hz using the double bunch operation mode. It increases twice the experiments throughput of the facility with modest additional investment. Two electron bunches spaced 28 ns apart are extracted from the cathode by two laser pulses with individually controlled repetition rates. The bunches are accelerated up to about 3 GeV in the main linac using the same rf macropulse. After separation, one bunch serves the Athos soft x-ray beamline and the other is further accelerated to serve the hard x-ray beamline – Aramis. A fast and high-stability beam kicker separates the two bunches without disturbing the electron beam and consequently the x-ray lasing. The timing and control system sets hybrid machine modes utilizing independent operation of the two undulator lines with individually programmed repetition rates. Beam diagnostics and feedback systems have to operate with two closely spaced bunches where the two beams share the same machine path. The low-level rf system manipulates the rf amplitude and phase within a fraction of the rf macropulse to provide decoupling of the acceleration parameters of the first and the second bunch. This manuscript presents measurements that show that the bunch separation does not degrade FEL lasing stability.

We present high-resolution measurements of the electron beam energy spread at the SwissFEL injector as a function of the electron bunch charge, the optics, and the longitudinal dispersion of the lattice. The measured values are in general an order of magnitude higher than what is predicted by standard simulation codes. The measured dependences indicate that the energy spread blowup is caused primarily by intrabeam scattering and microbunching instabilities, effects not covered in the conventional modeling of radio-frequency injectors. We present further a numerical model that qualitatively reproduces the experimental data and an approach to mitigate the energy spread deterioration. The work underlines the importance of considering the energy spread in the optimization and design of high-brightness electron beam sources and the need to develop new models to adequately understand and simulate the observed physics effects.

X-ray free-electron lasers (XFELs), with pulse durations of a few tens of femtoseconds or shorter, are cutting-edge instruments capable of observing structure and dynamics at the atomic scale. Temporal diagnostics are challenging but of fundamental importance for XFEL performance and experiments. In this paper, we demonstrate a method to characterize on a single-shot basis the temporal profile of both the electron beam and the XFEL radiation with femtosecond resolution. The approach consists in streaking the electron beam after the undulator using the wakefields of a corrugated structure. Its merits are arrival time stability and cost-effectiveness. Our method allows access to self-synchronized femtosecond diagnostics to any XFEL facility at low cost.

This report describes the accelerator physics aspects, the engineering considerations and the choice of parameters that led to the accelerator design of the FERMI Free-Electron-Laser. The accelerator (also called the "electron beam delivery system") covers the region from the exit of the injector to the entrance of the first FEL undulator. The considerations that led to the proposed configuration were made on the basis of a study that explored various options and performance limits. This work follows previous studies of x-ray FEL facilities (SLAC LCLS [1], DESY XFEL [2], PAL XFEL [3], MIT [4], BESSY FEL[5], LBNL LUX [6], Daresbury 4GLS [7]) and integrates many of the ideas that were developed there. Several issues specific to harmonic cascade FELs, and that had not yet been comprehensively studied, were also encountered and tackled. A particularly difficult issue was the need to meet the requirement for high peak current and small slice energy spread, as the specification for the ratio of these two parameters (that defines the peak brightness of the electron beam) is almost a factor of two higher than that of the LCLS's SASE FEL. Another challenging aspect was the demand to produce an electron beam with as uniform as possible peak current and energy distributions along the bunch, a condition that was met by introducing novel beam dynamics techniques. Part of the challenge was due to the fact that there were no readily available computational tools to carry out reliable calculations, and these had to be developed. Most of the information reported in this study is available in the form of scientific publications, and is partly reproduced here for the convenience of the reader.

A study of the electron beam dynamics in the linac is conducted for the FERMI free electron laser (FEL) founded for construction at the Sincrotrone Trieste

We describe the machine layout and major performance parameters for the FERMI FEL project funded for construction at Sincrotrone Trieste, Italy, within the next five years. The project will be the first user facility based on seeded harmonic cascade FELs, providing controlled, high peak-power pulses. With a high-brightness rf photocathode gun, and using the existing 1.2 GeV S-band linac, the facility will provide tunable output over a range from ~;100 nm to ~;10 nm, with pulse duration from 40 fs to ~; 1 ps, peak power ~;GW, and with fully variable output polarization. Initially, two FEL cascades are planned; a single-stage harmonic generation to operate > 40 nm, and a two stage cascade operating from ~;40 nm to ~;10 nm or shorter wavelength. The output is spatially and temporally coherent, with peak power in the GW range. Lasers provide modulation to the electron beam, as well as driving the photocathode and other systems, and the facility will integrate laser systems with the accelerator infrastructure, including a state-of-the-art optical timing system providing synchronization of rf signals, lasers, and x-ray pulses. Major systems and overall facility layout are described, and key performance parameters summarized.

Several beam manipulation methods have been studied and experimentally demonstrated to generate x-ray multipulses in free-electron-laser (FEL) facilities, advancing the fields of material science, molecular physics, and photochemistry by enabling x-ray pump/x-ray probe experiments. We have demonstrated a novel method to generate hard x-ray multipulses using a hybrid compression scheme. Compared to other methods, this approach minimizes the time jitter among the FEL subpulses, produces large power FEL subpulses, is suitable for high repetition rate machines, since it does not imply the generation of losses, and it works at short and hard x-ray FEL wavelengths as well. All of these aspects make this approach attractive for the novel FEL facilities aiming to explore the hard x-ray region and to work at high repetition rate.

The SAXS and SANS techniques are widely applied to the structural characterization of materials at the nanometer scale. We here report quantitative analyses of the published literature related to these techniques and to relevant features of the International SAS Conferences. A total number of 42,048 articles related to SAXS and SANS were retrieved. The annual total number of published articles related to SAXS exhibits a fast and persistent growth from 1990 until 2018 while those referring to SANS remained essentially constant along the past two decades. Furthermore, the number of citations of articles published by authors from the USA and from some European countries (Germany, France, UK) are significantly higher than those published by authors from other countries. The persistent increase in the number of published articles related to SAXS around the world and particularly in Brazil is well correlated with the also increasing number of open synchrotron sources.

A collaboration between DESY, PSI and CERN has developed and built an advanced modular X-band transverse deflection structure (TDS) system with the new feature of providing variable polarization of the deflecting force. The prototype of the novel X-band TDS, the polarizable X-band (PolariX) TDS, was fabricated at PSI following the high-precision tuning-free production process developed for the C-band Linac of the SwissFEL project. Bead-pull rf measurements were also performed at PSI to verify, in particular, that the polarization of the dipole fields does not have any rotation along the structure. The high-power test was performed at CERN and now the TDS is at DESY and has been installed in the FLASHForward beamline, where the first streaking experience with beam has been accomplished. We summarize in this paper the rf design of the TDS and its key components, such as the X-band pulse compressor, E-rotator, and phase shifter, the results of the bead-pull measurements and the high power test and finally the rf setup at DESY.

We report on the generation of one- and two-color attosecond hard x-ray pulses at SwissFEL by appropriately tailoring the nonlinear compression of the electron beam. For achieving very short [about 300 attoseconds (as)] and stable single-color pulses, we minimize the collective effects of the longitudinal space-charge forces by strongly compressing the electron beam right before the undulator, utilizing the energy collimator chicane as a third compression stage. For achieving two-color short pulses, we exploit enhanced space-charge forces splitting the beam into two energy components.

The dark current emitted from a surface of a radio frequency cavity may be a severe issue for the activation and the protection of the components of linear accelerators, if this current is lost in an uncontrolled manner. For a single-pass linac based on a photo-injector, we studied the possibility of using a collimator installed at low energy (below 10 MeV) to dump the maximum fraction of the dark current before it is transported along the linac. We developed and experimentally verified an emission and tracking model that we used to study and optimize the dark current mitigation at SwissFEL test facility. We optimized a collimator, which is expected to reduce by two orders of magnitude the transport of the dark current to the first compressor. We have also verified the effects of wakefield excited by the beam itself passing through the collimator at such a low energy, comparing the results of beam-based measurements with an analytical model.

Laser treatment technologies have been widely used to modify superficial layers of different materials. In this work we prepare Nb and Cr rich coatings according to laser alloying technique using cast iron as substrate material. Nb and Cr are intensive used in order to overcome challenges like good chemical and mechanical performance at high temperatures. Following laser alloying the surface-modified samples were submitted to an "in situ" XRD analysis under controlled high temperature and atmosphere. The phase transitions registered point to transformations that do not implies formation of fragile phases or cracks induced by high volumes modifications.

Structural characterisations using the SAXS technique in a number of nanoheterogeneous materials and liquid solutions are reviewed. The studied systems are protein (lysozyme)/water solutions, colloidal ZnO particles/water sols, nanoporous NiO-based xerogels, hybrid organic-inorganic siloxane-PEG and PPG nanocomposites and PbTe semiconductor nanocrystals embedded in a glass matrix. These investigations also focus on the transformations of time-varying structures and on structural changes related to variations in temperature and composition. The reviewed investigations aim at explaining the unusual and often interesting properties of nanostructured materials and solutions. Most of the reported studies were carried out using the SAXS beamline at the National Synchrotron Light Laboratory (LNLS), Campinas, Brazil.

The SwissFEL X-ray Free Electron Laser (XFEL) facility started construction at the Paul Scherrer Institute (Villigen, Switzerland) in 2013 and will be ready to accept its first users in 2018 on the Aramis hard X-ray branch. In the following sections we will summarize the various aspects of the project, including the design of the soft and hard X-ray branches of the accelerator, the results of SwissFEL performance simulations, details of the photon beamlines and experimental stations, and our first commissioning results.

The SwissFEL Injector Test Facility operated at the Paul Scherrer Institute between 2010 and 2014, serving as a pilot plant and test bed for the development and realization of SwissFEL, the x-ray Free-Electron Laser facility under construction at the same institute. The test facility consisted of a laser-driven rf electron gun followed by an S-band booster linac, a magnetic bunch compression chicane and a diagnostic section including a transverse deflecting rf cavity. It delivered electron bunches of up to 200 pC charge and up to 250 MeV beam energy at a repetition rate of 10 Hz. The measurements performed at the test facility not only demonstrated the beam parameters required to drive the first stage of an FEL facility, but also led to significant advances in instrumentation technologies, beam characterization methods and the generation, transport and compression of ultralow-emittance beams. We give a comprehensive overview of the commissioning experience of the principal subsystems and the beam physics measurements performed during the operation of the test facility, including the results of the test of an in-vacuum undulator prototype generating radiation in the vacuum ultraviolet and optical range.

The design of a photoinjector, in particular that of the electron source, is of central importance for free electron laser (FEL) machines where a high beam brightness is required. In comparison to standard designs, an rf traveling-wave photocathode gun can provide a more rigid beam with a higher brightness and a shorter pulse. This is illustrated by applying a specific optimization procedure to the SwissFEL photoinjector, for which a brightness improvement up to a factor 3 could be achieved together with a double gun output energy compared to the reference setup foreseeing a state-of-the-art S-band rf standing-wave gun. The higher brightness is mainly given by a (at least) double peak current at the exit of the gun which brings benefits for both the beam dynamics in the linac and the efficiency of the FEL process. The gun design foresees an innovative coaxial rf coupling at both ends of the structure which allows a solenoid with integrated bucking coil to be placed around the cathode in order to provide the necessary focusing right after emission.

A complete characterization of the time-resolved longitudinal beam phase space is important to optimize the final performances of an accelerator, and in particular this is crucial for Free Electron Laser (FEL) facilities. In this paper we propose a novel method to characterize the profile of a relativistic electron bunch by passively streaking the beam using its self-interaction with the transverse wakefield excited by the bunch itself passing off-axis through a dielectric-lined or a corrugated waveguide. Results of a proof-of-principle experiment at the SwissFEL Injector Test Facility are discussed.