This PDF file contains the front matter associated with SPIE Proceedings Volume 8078, including the Title Page, Copyright information, Table of Contents, Introduction, and the Conference Committee listing.

After less than two years of commissioning the FERMI@Elettra free electron laser is now entering into the operation phase and is providing light to the first user experiments. To reach the final ambitious goals of providing high power coherent pulses with fundamental wavelengths down to 4 nm, the system will need further studies and additional commissioning time in 2011 when fine tuning of the major systems such as the electron gun and the main accelerator will take place. Nevertheless, FERMI is already able to provide light with unique characteristics allowing Users to perform experiments not possible with other facilities. Based on a 1.5 GeV electron linear accelerator, FERMI@Elettra has two seeded FEL lines that cover the whole spectral range from 100 nm down to 4 nm with fully coherent pulses. The use of the high gain harmonic generation scheme initiated by a tunable laser in the UV allows FERMI to produce light characterized by both transverse and full temporal coherence. The use of specially designed undulators allows full control of the FEL polarization and can be continuously varied from linear to circular in any orientation or ellipticity. Here we will report about the first results and the future plans for FERMI@Elettra.

The planned XFEL at the Paul Scherrer Institut, the SwissFEL, is a fourth generation light source. Meanwhile the first hard X - ray FEL was taken into operation, the LCLS at Stanford, USA. Two further hard XFELs are in construction. One in Hamburg, Germany and the second at Spring - 8, Japan. Thanks to the beam properties of the XFEL, these new sources promise to bring novel insights and breakthroughs in many scientific disciplines. For engineers and designers new challenges arise in terms of material choice, damage thresholds and beam property conservation. The Swiss Light Source optics group is currently working on the beamline optics design of the SwissFEL beamlines. The preliminary optics design of the two undulator beamlines which serve six experiments is under preparation. In this article a preliminary layout of the hard X - ray Aramis undulator beamline is presented. Several beamline designs have been evaluated. Beam deflection and splitting via mirrors and diamonds is presented. The SwissFEL is planned to be operational in 2016.

Results of coherent diffractive imaging experiments performed with soft X-rays (1-2 keV) at the Linac Coherent Light Source are presented. Both organic and inorganic nano-sized objects were injected into the XFEL beam as an aerosol focused with an aerodynamic lens. The high intensity and femtosecond duration of X-ray pulses produced by the Linac Coherent Light Source allow structural information to be recorded by X-ray diffraction before the particle is destroyed. Images were formed by using iterative methods to phase single shot diffraction patterns. Strategies for improving the reconstruction methods have been developed. This technique opens up exciting opportunities for biological imaging, allowing structure determination without freezing, staining or crystallization.

We developed a multipurpose vacuum chamber which function is to be used in the pump/probe diffraction / scattering and spectroscopy experiments with free electron laser (FEL) radiation. By using a liquid jet setup to deliver the sample into the chamber it is possible to overcome the difficulties coming from the fact that a single shot of the FEL radiation is sufficient to induce irreversible damage to the sample. The refreshment of the sample allows for the experiments with the repetition rate of up to the MHz regime. The liquid jet nozzle size will be in the sub-micrometer range. This multipurpose chamber is in particular suited for chemistry and biochemistry experiments in solution.

Experiments performed in a Free Electron Laser (FEL) facility can require a selection of higher harmonics; a typical example is the pump and probe experiments in which the system under test is pumped with a fundamental wavelength and probed with its third harmonic. The wavelengths selection performed by a monochromator can affect beam properties such as wavefront deformation or time elongation and its usage in the beam manipulation should be avoided. Nevertheless, for a limited number of wavelengths, the selection can be performed using periodic multilayer coatings (MLs) with the reflectivity peak tuned at the desired harmonic: this technique is already foreseen at the new FERMI@Elettra FEL facility for selecting 20nm, 16nm, 13.5nm and 6.66nm harmonics. In order to improve the fundamental rejection, the MLs have been overcoated by different capping-layers; in particular at shortest wavelength higher rejection ratio have been obtained by the use of a third absorbent material in the capping layer. However, this same approach has not showed considerable improvements at the longest wavelengths, where interferential aperiodic capping-layers designed using a method based on the control of standing wave distribution are to be preferred.

X-ray mirrors are needed for beam steering, beam alignment and monochromatisation at advanced research light sources like 3rd generation synchrotron sources (e.g. PETRA III in Hamburg) or Free-Electron Lasers (for instance FLASH or the European XFEL). At the Helmholtz-Zentrum Geesthacht (formerly GKSS), an in-house designed magnetron sputtering facility for the deposition of single layers and multilayers has been installed for the development of x-ray optics. Earlier results showed that the thin-film fabrication of 1.5 m long amorphous carbon coatings was very successful. These single layers are currently used as total reflection mirrors at FLASH to steer the photon beam to the various beamlines. A major advantage of the sputtering facility is that it is now possible to prepare one, two or more mirrors with similar properties over the whole deposition length. In this contribution we present results for the x-ray optical properties of C, B4C and W coatings and W/C multilayers. The goal of the development of x-ray mirrors is to optimize the deposition conditions in order to control the thickness of a single layer or the lateral period of a multilayer, and to achieve high reflectivity over the whole deposition length according to the application.

One of the most challenging tasks for the FEL photon diagnostics is the precise determination of the FEL pulse duration - maybe even getting information on the substructure of the SASE pulses. The knowledge of the temporal pulse characteristics is not only important for nonlinear interactions which rely purely on the correct determination of the intensity, but also to gain insight on the dynamics of the investigated processes. Here, the resolution of pump-probe experiments relies heavily on knowledge of the pulse duration for one-color pumpprobe and in addition on the precise arrival time difference for two-color pump-probe experiments. Due to the wide range of available parameters at the existing and planed FELs the photon energies are ranging from VUV to X-rays with pulse durations of few fs or even sub fs range up to pulses with several 100 fs pulse duration. Thus, a variety of methods has to be investigated and utilized in order to characterize the temporal structure of these pulses. Moreover due to the statistical nature of the SASE process the pulse shape (consisting of few up to hundreds of sub-pulses) varies from pulse to pulse. Here, techniques to characterize the pulse shot by shot are needed - increasing the level of complexity in contrast to averaging techniques by far. An overview of the different techniques is given in this text.

The Italian Free Electron Laser (FEL) facility FERMI@Elettra has started to produce photon radiation at the end of 2010. The photon beam is presently delivered by the first undulator chain (FEL1) that is supposed to produce photons in the 100-20 nm wavelength range. A second undulator chain (FEL2) will be commissioned at the end of 2011, and it will produce radiation in the 20-4nm range. The Photon Analysis Delivery and Reduction System (PADReS) was designed to collect the radiation coming from both the undulator chains (FEL1 and FEL2), to characterize and control it, and to redirect it towards the following beamlines. The first parameters that are checked are the pulse-resolved intensity and beam position. For each of these parameters two dedicated monitors are installed along PADReS on each FEL line. In this way it possible to determine the intensity reduction that is realized by the gas reduction system, which is capable of cutting the intensity by up to four orders of magnitude. The energy distribution of each single pulse is characterized by an online spectrometer installed in the experimental hall. Taking advantage of a variable line-spacing grating it can direct the almost-full beam to the beamlines, while it uses a small fraction of the beam itself to determine the spectral distribution of each pulse delivered by the FEL. The first light of FERMI@Elettra, delivered to the PADReS section in late 2010, is used for the first commissioning runs and some preliminary experiments whose results are reported and discussed in detail.

The wavefront as well as beam parameters of the free electron laser FLASH emitting in the EUV spectral range were determined from wavefront measurements using self supporting Hartmann sensors. The devices were applied for alignment of the ellipsoidal focusing mirror at Beamline 2 (BL2), reducing the rms wavefront aberrations by more than a factor of 3. Beam quality M² and other beam parameters were evaluated from wavefront and intensity data delivered by the Hartmann sensor. Furthermore, 100 two-dimensional single pulse intensity distributions were recorded at each of 32 axial positions, spaced app. ±2 Rayleigh lengths around the waist of the optimized FEL beam with a magnifying EUV sensitized CCD camera. From these beam profile data the Wigner distribution function was reconstructed on two dimensional orthogonal subspaces. For separable beams this yields the complete Wigner distribution and gives comprehensive and high-resolution information on the propagation characteristics, including wavefront, mode content and spatial coherence. The wavefront of the optimized beam evaluated at waist position was in the order of λ?4 peak valley, whereas a significant contribution of uncorrelated higher order Hermite-Gauss modes and a global degree of coherence of 0.12 can be detected, leading to a substantial increase of the M² factor, which was determined to ~ 4.2 and ~ 3 in the horizontal and vertical direction, respectively. The obtained results are compared to the Hartmann experiments.

The high intensity of free-electron lasers now allows for the possibility of obtaining measurable diffraction from biological samples with a single X-ray pulse. An important consequence of diffract-before-destroy imaging is that the sample is destroyed and therefore must be replaced preferably at the repetition rate of the FEL. This presents an interesting challenge; the sample must be rapidly replaced within the X-ray focus at the proper particle density and degree of hydration without damaging or denaturing the sample. If particle number density is too high, for example due to clustering or evaporation, the diffraction pattern resulting from coherent illumination of multiple particles may be discarded when sorting for 3D reconstruction. If number density is too low the hit rate, percentage of pulses with measurable scattered intensity, may also be too low to collect a complete data set. Evaporation will also leave behind less volatile material and this change of concentration may be damaging to the sample. On the other hand the similarity in electron density for water and biological material provides poor contrast for fully hydrated material. It is often also necessary to consider sample consumption. While high, near unity, hit rate can be obtained using liquid jets, a liquid flow rate greater then 1 microliter per minute must be maintained. Several sample injection possibilities, drop on demand, aerosols, liquid jets, aerodymamic lenses, have been explored and a review of these results is presented.

The current development of novel fast X-ray imagers for X-ray Free Electron Laser (XFEL) radiation sources raises the need for suitable characterization tools for studying and qualifying detector performance over a wide range of injection levels. In particular it is needed to assess detector's timing properties and achievable spatial resolution through a detailed 2D mapping of the detector response at any level of charge injection. To this aim a high-dynamic range test suite has been devised and implemented. At the lower levels of charge injection the stimulus comes from a laser test bench, while for the higher levels of charge injection we make use of mono-energetic proton bunches. Deconvolution methods have been developed for the detector output waveforms in order to gain deeper insight on detector behavior. This paper will discuss the potential of the developed suite as a diagnostic tool for mapping the response of the detectorfrontend system in charge, time and space at high resolution through the illustration of an extended qualification campaign carried out on a prototype of Multi Linear Silicon Drift Detector with high readout speed.

In the x-ray wavelengths, the two leading FEL concepts are the self-amplied spontaneous emission (SASE) conguration and the high-gain harmonic generation (HGHG) scheme. While the radiation from a SASE FEL is coherent transversely, it typically has rather limited temporal coherence. Alternatively, the HGHG scheme allows generation of fully coherent radiation by up-converting the frequency of a high-power seed laser. However, due to the relatively low up-frequency conversion eciency, multiple stages of HGHG FEL are needed in order to generate x-rays from a UV laser. The up-frequency conversion eciency can be greatly improved with the recently proposed echo-enabled harmonic generation (EEHG) technique. In this work we will present the concept of EEHG, and address some practically important issues that aect the performance of the seeding. We show how the EEHG can be incorporated in the FEL scheme and what is the expected performance of the EEHG seeded FEL. We will then brie y describe the rst proof-of-principle EEHG experiment carried out at the Next Linear Collider Test Accelerator (NLCTA) at SLAC. We will also discuss latest advances in the echo-scheme approach, and refer to subsequent modications of the original concept.

Due to start-up from shot noise, typical SASE XFEL pulses exhibit poor longitudinal coherence. Self-seeding schemes can be use to improve it. Recently, a novel single-bunch self-seeding scheme was proposed, based on a particular kind of monochromator, which relies on the use of a single crystal in Bragg-transmission geometry. In its simplest configuration, the self-seeded XFEL consists of an input undulator and an output undulator separated by such monochromator. However, in some experimental situations this simplest two-undulator configuration is not optimal. The obvious and technically possible extension is to use a setup with three or more undulators separated by monochromators. This amplification-monochromatization cascade scheme is distinguished, in performance, by a small heat-loading of crystals and a high spectral purity of the output radiation, and is particularly advantageous for the European XFEL. The power of the output signal can be further increased by tapering the magnetic field of the undulator. Once the cascade self-seeding scheme is combined with tapering in a tunable-gap baseline undulator at the European XFEL, a source of coherent radiation with unprecedented characteristics can be obtained at hard X-ray wavelengths, promising complete longitudinal and transverse coherence, and a peak brightness three orders of magnitude higher than what is presently available at LCLS. Additionally, the new source will generate hard X-ray beams at extraordinary peak (TW) and average (kW) power level. The proposed source can thus revolutionize fields like single biomolecule imaging, inelastic scattering and nuclear resonant scattering. Our self-seeding scheme is extremely compact, and takes almost no cost and time to be implemented. The upgrade proposed in this work could take place during the commissioning stage of the European XFEL, opening a vast new range of applications from the very beginning of operations. We present feasibility study and exemplifications for the SASE2 line of the European XFEL.

The Max Planck Advanced Study Group (ASG) at the Center for Free Electron Laser Science (CFEL) has designed the CFEL-ASG MultiPurpose (CAMP) instrument, which provides a unique combination of particle and photon detectors for experiments at 4^th generation light sources. In particular, CAMP includes two sets of newly developed 1024 × 1024 pixel pnCCD imaging detector systems. The CAMP instrument has now been successfully employed during the first three beam times at LCLS, and we report here on practical experience gained for the operation of imaging pnCCD detectors at FEL facilities. We address a wide range of topics: pnCCD gain and energy calibration during experiments; suppression of optical light contamination in pumpprobe experiments; contamination of the pnCCD entrance window with sample material; effects of accidental direct impact on the pnCCDs of particles generated by the FEL beam impinging on the experimental setup; and the effect of accidental direct exposure of a pnCCD to the focused and unattenuated X-ray beam. These lessons learned will help us to further improve operation of pnCCDs in future FEL experiments.

Measurement campaigns of the Max-Planck Advanced Study Group (ASG) in cooperation with the Center for Free Electron Laser Science (CFEL) at DESY-FLASH and SLAC-LCLS have established pnCCDs as universal photon imaging spectrometers in the energy range from 90 eV to 2 keV. In the CFEL-ASG multi purpose chamber (CAMP), pnCCD detector modules are an integral part of the design with the ability to detect photons at very small scattering angles. In order to fully exploit the spectroscopic and intensity imaging capability of pnCCDs, it is essentially important to translate the unprocessed raw data into units of photon counts for any given position on the detection area. We have studied the performance of pnCCDs in FEL experiments and laboratory test setups for the range of signal intensities from a few X-ray photons per signal frame to 100 or more photons with an energy of 2 keV per pixel. Based on these measurement results, we were able to characterize the response of pnCCDs over the experimentally relevant photon energy and intensity range. The obtained calibration results are directly relevant for the physics data analysis. The accumulated knowledge of the detector performance was implemented in guidelines for detector calibration methods which are suitable for the specific requirements in photon science experiments at Free Electron Lasers. We discuss the achievable accuracy of photon energy and photon count measurements before and after the application of calibration data. Charge spreading due to illumination of small spots with high photon rates is discussed with respect to the charge handling capacity of a pixel and the effect of the charge spreading process on the resulting signal patterns.

New generation synchrotron light sources, the X-ray free electron lasers, require a two dimensional focal plane instrumentation to perform X-ray imaging from below 100eV up to 25keV. The instruments have to face the accelerator bunch structure and energy bandwidth which is different for existing (FLASH, Hamburg and LCLS, Menlo Park) and future photon sources (SACLA, Harima and XFEL, Hamburg). Within the frame of the Center for Free Electron Laser Science (CFEL), a joint effort of the Max-Planck Society, DESY and the University of Hamburg, the MPI semiconductor laboratory developed, produced and operated large area X-ray CCD detectors with a format of nearly 60cm² image area. They show outstanding characteristics: a high readout speed due to a complete parallel signal processing, high and homogeneous quantum efficiency, low signal noise, radiation hardness and a high pixel charge handling capacitance. We will present measurement results which demonstrate the X-ray spectroscopic and imaging capabilities of the fabricated devices. We will also report on the concept and the anticipated properties of the full, large scale system. The implementation of the detector into an experimental chamber to perform measurements e.g. of macromolecules in order to determine their structure at atomic resolutions will be shown.

The intensity of the radiation produced by a Free Electron Laser (FEL) is more intense, coherent, and with much higher photon density with respect to the radiation generated by storage rings undulators. FERMI@Elettra will use a seeding technique which provides near Gaussian temporal structure of the pulse with a bandwidth close to the transform limit. In order to preserve the properties of such pulse, the beam manipulation towards the ending station is performed by the use of multilayer coatings (MLs). The primary application is in the delay line systems, useful in pump and probe experiment: the beam is split and one of the arm is equipped with multilayer mirrors which are able to reject the fundamental harmonic, selecting the third; the two beams are then recombined and the relative delay can be controlled by changing the mirrors distance. Specific designs and working principle of such MLs are presented elsewhere. In this work the time delay of pulse travelling in the nanostructures is investigated and photoemission experiment applied to its evaluation conceived. MLs are also studied for verifying their possible application in a phase shifter set-up, useful to have control of the source polarization or to produce elliptical and circularly polarized light. In this way, the FELs circular polarized radiation, which is emitted out of the electron plane and therefore it is very difficult to be manipulated, can be generated from a plane pulse linearly polarized.