A high temporal stability of produced photon pulses is a key parameter for some classes of experiments, e.g., those using a pump-probe scheme. A longitudinal intra bunch-train feedback system, that reduces the intra bunch-train and the train-to-train arrival time fluctuations down to the sub-10 fs level was implemented at the European X-ray free electron laser (EuXFEL). The low arrival time...
This project describes different techniques to manufacture THz mirrors with arbitrary surfaces. The research is part of the development of THz transmission line for the compact FEL-THz accelerator.
As an initial phase flat mirrors were 3D printed with FFF (Fused Filament Fabrication) and SLA (Stereolithography Apparatus). The impact of material, layer height and layer direction to mirror’s...
Free electron lasers (FEL) serve a broad user community in many scientific fields ranging from
atomic and molecular physics to plasma and solid state physics as well as chemistry and biology.
Many experiments could benefit from a non-destructive online photon diagnostic of the provided
x-ray pulses. Especially, for free-electron lasers that are operated in the self-amplified sponta-
neous...
For a free-electron laser facility, the longitudinal phase space of the beam is essential to the FEL lasing performance. However, the commonly-used diagnostics device such as the transverse deflecting cavity provides a destructive way to measure the beam longitudinal properties, which is not available during beam delivery. Thus, the convolutional neural network is introduced to construct a...
Optimal FEL gain in a seeded FEL requires the careful alignment of different components. As for SASE FELs, the gain is optimized when the electron bunch travels in a straight line along the axis of each undulator in the radiator section. We have recently developed an alignment strategy for the optimization of the FERMI FELs which combines the beam-based alignment of the magnetic elements...
X-ray absorption spectroscopy (XAS) enables the study of the electronic and geometric structural properties of matter. Such investigations can now be realized with femtosecond temporal resolution owing to the availability of X-ray free-electron lasers (XFELs) [1]. However, most XFELs currently utilize self-amplified spontaneous emission (SASE), which causes strong shot-to-shot fluctuations of...
The European X-ray Free-Electron Laser (EuXFEL) is a unique FEL facility that provides X-ray pulses of high spectral brilliance and high photon flux at MHz repetition rate. However, the high peak power, produced in trains of up 2700 femtosecond pulses at a rate of 10 Hz, induces a periodic temperature increase of the hard X-ray monochromators, thereby reducing their transmitted intensity. To...
PolFEL will be the first free-electron laser facility in Poland. It will be driven with RF continuous-wave superconducting linac including an SRF injector furnished with a lead film superconducting photocathode. PolFEL will provide a wide wavelength range of electromagnetic radiation from 0.6 mm down to 60 nm. The linac will be split into three branches. Two of them will feed undulators chains...
The electron-beam properties needed for successful implementation of a free-electron-laser oscillator (FELO) on a superconducting TESLA-type linac at the Fermilab Accelerator Science and Technology (FAST) facility include the intrinsic normalized emittance and the submacropulse centroid stability. We have demonstrated that short-range wakefields (SRWs) and long-range wakefields including...
A helical undulator provides a stronger FEL coupling than common planar geometries as the beam’s transverse velocity never vanishes. However, a significant challenge lies in tuning and measuring the fields with limited access to the beam axis along the undulator. Confirming the good field region off axis is difficult without space for 3D hall probe scans, and is important for low energy beams...
We present experimental observation for the impact of an introduced orbit disturbance in the photoinjector section on the SASE performance at the European XFEL. An orbit bump is first created and then closed by the orbit feedback downstream, that is, the orbit leaving the injector section stays the same while presumably only causing a disturbance to the bunch. With the same orbit launched into...
Electrons in a X-ray free electron laser (XFEL) develop periodic density fluctuations, known as microbunches, which enable the exponential gain of X-ray power in an XFEL. When an electron beam microbunched at a hard X-ray wavelength is kicked, microbunches are often washed out due to the dispersion and R56 of the bend. An achromatic (dispersion-free) bend with small R56, however, can...
It has been proposed that a new arc, called T20, should be installed for a third fan of undulators at the EuXFEL in the next decade. Due to geometric constraints this arc will need to be at a much larger angle than for the existing arc (T1). It is expected therefore that coherent synchrotron radiation effects in T20 on the bunch emittances will be considerable. To preserve the x-ray beam...
It is planned to extend SwissFEL by a third beamline, named Porthos, operating in the hard X-ray regime. Three bunches will be accelerated within one RF pulse and distributed into the different beamlines with resonant kickers operating at the bunch spacing of a few tens of nanoseconds.
While the full extent of Porthos will not be realized before the end of this decade the extraction line from...
The ORGAD Hybrid RF-gun which was commissioned in Ariel University is based on a smaller-scale prototype built at UCLA's Particle Beam Physics Laboratory (PBPL) as an on-going collaboration between the Universities. The main beamline of the hybrid S-band (2856 [MHz]) photo injector is currently driving a 150[kW], short pulse THz-FEL. In order to use the RF gun for other applications, a new and...
Kyma S.p.A. was awarded the design and production of the APPLE-X undulator for SABINA project at INFN - Laboratori Nazionali di Frascati. SABINA (Source of Advanced Beam Imaging for Novel Applications) is a project aimed at the enhancement of the SPARC_LAB research facility. The two user lines that are going to be implemented are; a power laser target area and a THz radiation line.
Here we...
EuPRAXIA@SPARC_LAB is a new Free Electron Laser (FEL) facility that is currently under construction at the Laboratori Nazionali di Frascati of the INFN. Fermilab is contributing to the project with the design, manufacturing and qualification of a prototype conduction cooled superconducting undulator (SCU) that, if successful, could be integrated in the final machine.
The design of the SCU...
Terahertz (THz) radiation may pass through dielectric materials, and this ability can be used for a variety of applications. Terahertz (THz) radiation is located between infrared and microwave radiations in the electromagnetic spectrum. FEL produces brief, high-power THz single pulses, and we provide a diagnostic approach for them. The electro optic efficacy is used as a detection method. For...
Development and characterization of an angle-resolved photo-electron spectrometer, based on the electron Time-of-Flight concept, designed for hard X-ray photon diagnostics at the European free-electron laser is described. The objective with the instrument is to provide beamline users and operators with pulse resolved, non-invasive spectral distribution diagnostics, which in the hard X-ray...
We were able to realize a compact microtron accelerator with 5 MeV electron beam acceleration energy and a hybrid electro-magnetic undulator that can vary the magnetic field of 1.07 T at 0.74 T. The electron beam is accelerated by an RF electric field of a 1-cell acceleration cavity and recirculated by a uniform magnetic field of the microtron main chamber. Through the re circulation process,...
FELs deliver rapid pulses on the femtosecond scale, and high peak intensities that fluctuate strongly on a pulse-to-pulse basis. The fast drift velocity and high radiation tolerance properties of chemical vapor deposition (CVD) diamonds make these crystals a good candidate material for developing a high frame rate pass-through diagnostic for the next generation of XFELs. We report on two...
PolFEL stands for Polish Free Electron Laser, the first FEL research infrastructure in Poland. This facility is under development, and it will operate in three wavelength ranges: IR, THz and VUV, using different types of undulators. Machine will be driven by 200 MeV linear superconducting accelerator, which will operate in both, pulsed wave (PW) and continuous wave (CW) modes. This...
At the Photo Injector Test facility at DESY in Zeuthen (PITZ) photo electron guns for the use at the X-ray free-electron laser (FEL) facilities FLASH and European XFEL are conditioned. An electron beam with high current and low transverse emittance is required for high performance in an X-ray FEL.
As the lasing process occurs on the part of the electron bunch with the highest charge density...
Diffraction gratings are an essential instrument used at free-electron laser facilities in soft and tender x-ray ranges. Their application ranges from monochromators and analyzers to self-seeding and pulse compression. These gratings are typically around 50-200 mm, up to 500mm in length with pitches from a few micrometers down to a few 100 nm, made on flat or curved substrates. Blazed gratings...
Co-propagating a relativistic electron beam and a high-power laser pulse through a short undulator (modulator) provides an energy modulation which can be converted to a periodic longitudinal density modulation (or microbunching) via the R56 term of a chicane. Such pre-bunching of a beam at the resonant wavelength and the harmonics of a subsequent free-electron laser (FEL) amplifier seeds the...
The presence of microbunching in the FERMI FEL electron beam is a known nuisance that can impact the performance of the FEL. Microbunching is generated by complex dynamics along the machine where there are several amplification sources. The use of a laser heater, at the cost of an increased energy spread, can improve the quality of the electron beam mitigating the modulation due to...
Intrabeam scattering (IBS) causes growth of the uncorrelated energy spread of electron bunches due to multiple small-angle Coulomb collisions over long propagation distances. As such, this effect may be a limiting factor for the beam current and therefore for the achievable photon energy in the SASE process. In addition, IBS influences the noise spectrum of the bunch, thus, interfering with...
The European X-Ray Free Electron Laser (XFEL) operates three Undulator Systems to generate high-brilliance and high repetition X-ray pulses. Each System consists of multiple 5-m long undulator segments separated by 1.1-m long intersections. Such intersections contain vacuum systems, diagnostic and correction equipment for the electron's trajectory, and phase shifters (PS) [1] to match the...
Ultra-short X-ray pulses in an XFEL can be generated by means of a slotted foil inserted into a bunch compressor. There is an ongoing study into whether such a technique could be used at the European XFEL. One important factor that must be considered is whether the additional beam losses and radiation load caused by the foil is acceptable with a high repetition rate of up to 4.5MHz at the...
The tremendous developments on Laser Plasma Accelerators (LPAs) have significantly improved the electron beam properties and stability making it possible to drive a Free Electron Laser (FEL). We report on the electron beam transport and manipulation using the COXINEL beamline implemented at HZDR that has recently led to the first measurements of an LPA-based seeded FEL in the UV region. Our...
CLARA is an electron beam test facility being developed in phases at STFC Daresbury Laboratory. The first phase, with up to 35 MeV electron beam energy, has been operated since 2018 for a wide range of accelerator applications. The second phase, presently being installed, will expand the range of applications by taking the beam to 250 MeV energy and via a dog-leg to an experimental station...
The superconducting undulator (SCU) based on the second-generation high-temperature superconducting (HTS) tapes is a promising application for building tabletop free-electron lasers (FELs). The short period < 10 mm undulators with a narrow magnetic gap < 4 mm are especially relevant. The advantage of the HTS tape is that it shows both high critical current density and high critical magnetic...
Orbit response measurements in the soft X-ray beamline of Athos have shown coupling of the beam transport between the transverse planes, which is influenced by the on-axis field strength of the Apple-X undulator modules. A model reproduces this observation if a coupling term is included in the transport matrix of the undulator module. The presentation shows the estimate of the coupling...
Ultracold plasmas (UCPs) form a new exotic category of plasmas that can be produced by photo-ionizing laser-cooled atoms in a magneto-optical trap (MOT) near-threshold. With densities up to $10^{18}$ m$^{-3}$, temperatures as low as $\sim$100 $\mu$K for the ions, and $\sim$1 K for the electrons, they are the ideal model plasmas to study fundamental processes in plasma physics, such as (the...
Electromagnetic wave undulators have the advantage of a shorter period compared with the permanent magnet undulators when operating at high frequency, therefore producing FEL radiation at the same wavelength with less electron energy. This paper investigates the properties of a Ka-band microwave undulator, and the factors that affect the choice of the high-power drive sources, through the...
Despite the use in machine physics of high-performance software for calculating and predicting machine parameters, when these are applied to the real world, optimal operating point search is often necessary to obtain the desired performance.
Furthermore, small configuration changes required by FEL Users during running experiments ,lead to search new good working points in a short time.
Use...
Currently 26 RF stations are in operation at the European X-ray Free Electron Laser (XFEL) and all RF stations can deliver sufficient power to reach maximum gradients in the accelerating modules, limited only by cavity and coupler properties. It was demonstrated that by activating a dynamic frequency shift (DFS) of the RF drive signal, the requested klystron power can be reduced by up to 20%,...
With the beam synchronous readout of the beam position measurement at the hard X-ray FEL beamline Aramis at SwissFEL we analyze the intrinsic orbit jitter, using a classification algorithm and Principal Component Analysis (PCA). The method sorts the jitter in a set of eigenvectors and -values. With the magnitude of the eigenvalues the impact of the different jitter sources can be estimated....
The undulators in the European XFEL are made of permanent magnets that need to be protected from beam losses that could cause demagnetisation. Under current operating conditions, beam losses in the undulators are prevented by a collimation section downstream of the main Linac and upstream of the switchyard. In the future, a slotted foil may be installed in the European XFEL to reduce the X-ray...
In January 2021 two X-band (12 GHz) PolariX Transverse Deflecting Structures with variable streak polarization were installed into the FLASH2 beamline at FLASH. Since none of the RF components for the FLASH2-PolariX RF-distribution system nor the two PolariX structures could be pre-conditioned, RF-conditioning was and is quite tedious. Nevertheless, after 6 weeks of conditioning, we have...
In 2017, a collaboration between DESY, PSI and CERN was established with the aim of developing and building seven advanced X-Band Transverse Deflection Structure (TDS) with the new feature of variable polarization of the deflecting force. Seven deflectors were produced by PSI of which five were installed in three experiments at DESY, while the remaining two were installed in the ATHOS soft...
We present the study for a short period Apple-X variable polarizing undulator, with small gap of operation and high magnetic field, which will be the base module for the AQUA line of the EuPRAXIA@SPARC_LAB FEL facility, of next realization at INFN Laboratory of Frascati. The undulator allows to achieve radiation between 3 and 5 nm, the so called water-window, with a 1 GeV electron beam energy,...
In this report, we present a simulation study of dielectric beam energy dechirper designed for the proposed NSRRC EUV FEL facility. As revealed from ELEGANT simulation of the high brightness driver linac system, a residual energy chirp of about 42 keV/m is left after bunch compression. It can be corrected by a capacitive dechirper structure when the bunch is slightly over-compressed. We...
The free-electron laser in Hamburg (FLASH) operates in the extreme ultraviolet (XUV) and soft X-ray region, providing photon pulses of few femtosecond (fs) duration and unprecedented intensity [1]. FLASH operates in the self-amplified spontaneous emission (SASE) regime, meaning that every pulse has a unique combination of energy, spectrum, arrival time and pulse duration. Therefore, it is...
We propose to develop an energy-recovery-linac (ERL)-based X-ray free-electron laser (FEL). Taking advantage of the demonstrated high-efficiency energy recovery of the beam power in the ERL, the proposed concept offers the following benefits: i) recirculating the electron beam through high-gradient SRF cavities shortens the linac, ii) energy recovery in the SRF linac saves the klystron power...
KAOS is the flagship optics of FERMI, the first - and presently only - fully seeded Free Electron Laser facility in the world. The name stands for Kirkpatrick-Baez Active Optical System, and it has been entirely developed in-house. After progressive revisions and upgrades, it presently empowers three out of six beamlines at FERMI, and it also serves two beamlines at FLASH, Hamburg (DiProI,...
The SASE3 soft X-ray beamline at the European XFEL is equipped with the grating monochromator allowing to reduce SASE FEL bandwidth and to improve longitudinal coherence at the experiments in the photon energy range 250 eV - 3000 eV. The design of the monochromator is challenged by a demand to control both photon energy resolution and temporal resolution; the aim to transport close to...
DEIMOS (Dichroism Experimental Installation for MagnetOptical Spectroscopies) is the beamline built at French Synchrotron SOLEIL facility intended for soft X-rays magnetic and natural dichroism spectroscopies. It has been designed to enable most challenging measurements in terms of X-rays sample sensitivity and signal detection level. The energies accessible on DEIMOS beamline rank from 350 eV...
Good control over the transverse distribution of an electron bunch is crucial for optimising the beam transport through a linear accelerator, and for improving the energy transfer of electrons to photons within the undulators of a free-electron laser (FEL). In order to achieve this, it is necessary to match, as closely as possible, the Twiss parameters of the electron bunch to the design...
Accurate and high resolution detection of the Longitudinal Phase Space (LPS) of the electron beam is a great advantage for operating and setting up a FEL. In the case of the soft X-ray FEL being proposed at the MAX IV synchrotron facility in Lund, this information is mainly supplied by a Transverse Deflecting Cavity (TDC) which is currently being installed and scheduled for commissioning in...
In free electron lasers (FEL) the accumulative effects of wakefields always lead to critical impacts on the electron bunch, resulting in an energy spread and deviation of transverse position. Thus the lasing performance will be decreased. The Shanghai high-repetition-rate XFEL and extreme light facility (SHINE) is under construction and the wakefields estimations are required. The SHINE...
