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A modified Depleted P-Channel Field Effect Transistor (DEPFET) is the key feature of the DEPFET Sensor with Signal Compression (DSSC), a 1 Mpixel X-ray camera aiming at ultra-fast imaging of soft X-rays at the European XFEL. Operation of large-area devices with a large number of DSSC-type DEPFET pixels requires the accurate knowledge of the sensitivity of the response to the relevant DEPFET parameters. The paper presents the experimental qualification of the response of DSSC-type DEPFET pixels in the space of 4 relevant parameters: drain current, source voltage, drain voltage and back side voltage. The obtained results allow estimation of the impact of the inevitable parameter fluctuations in large monolithic sensors and of the actual trimming range of the shape of signal compression in view of the pixelwise calibration of the 1 Mpixel DSSC camera. [ABSTRACT FROM AUTHOR]

When a modulated electron beam passes through the crystal it emits superradiant parametric X-ray emission (SPXE). Here we employ SPXE and demonstrate that it is possible to construct an X-ray resonator with a high Q-factor and the energy density inside. We thoroughly investigate the properties of this resonator and the feasibility of its experimental realization. [ABSTRACT FROM AUTHOR]

Highlights • Simulations reveal relaxation of keV electrons in metals toward equilibrium. • Faster electrons cause less radiation damage in femtosecond XFEL experiments. • Significant amount of secondary electrons generated near the Fermi surface. • Demonstrates quantum H-theorem in nonequilibrium statistical mechanics. Abstract Collisional relaxation of high-energy primary electrons (PEs) and generation of secondary electrons (SEs) in a metal are simulated self-consistently by the quantum Boltzmann equation taking into account dynamic screening. An efficient scheme to evaluate the multi-dimensional integral in the collision term is introduced, which enables one to compute time evolutions of nonequilibrium energy distribution functions over an energy range up to a few keV until the whole system reaches thermal equilibrium. Numerical results reveal that rapid energy loss of PEs by plasmon excitation occurs in an early stage, followed by a cascade excitation of SEs near the Fermi level. The overall energy distribution eventually converges to the equilibrium Fermi distribution of partially degenerate electron gas, corroborating the quantum-mechanical H -theorem; time evolutions of the corresponding nonequilibrium entropies are also simulated. The electron temperature and total number of SEs in the final state are consistent with thermodynamic values predicted from the initial energy density of PEs. The number of SEs excited during an early stage (initial 10 fs) turns out smaller for higher PE energies; this feature would bear relevance to an estimation of transient radiation damage in a metallic sample irradiated by an intense femtosecond x-ray laser pulse. [ABSTRACT FROM AUTHOR]

Abstract Petawatt class femtosecond lasers and x-ray free electron lasers (XFEL) open up a new page in research fields related to space and vacuum physics. One of fundamental principles can be explored by these new instruments is the equivalence principle, saying that gravitation and acceleration should be treated equivalently. If it is true this must lead to the appearance of the Unruh effect analogous to Hawking's black hole radiation. It says that a detector moving with a constant acceleration w sees a boson's thermal bath with its temperature T w = ℏ w / 2 π k B c. Practical detection of the Unruh effect requires extremely strong acceleration and fast probing sources. Here we demonstrate that x-rays scattering from highly accelerated electrons can be used for such detection. We present two, feasible for the Unruh effect, designs for highly accelerated systems produced in underdense plasma irradiated by high intensity lasers pulses. The first is Thomson scattering of a XFEL pulse from plasma wave excited by an intense laser pulse. Properly chosen observation angles enable us to distinguish the Unruh effect from the normal Doppler shift with a reasonable photon number. The second is a system consisting of electron bunches accelerated by a laser wake-field, as sources and as detectors, which move in a constantly accelerating reference frame (Rindler space) and are probed by x-ray free electron laser pulses. The numbers of photons is shown to be enough to observe reproducible results. [ABSTRACT FROM AUTHOR]

Synchrotron-radiation X-ray absorption spectroscopy (XAS) is a direct method for speciation analysis with atomic resolution, providing information about the local chemical environment of the probed element. This article gives an overview of the basic principles of XAS and its application to element speciation in biomedical research. The basic principle and experimental modalities of XAS are introduced, followed by a discussion of both its limitations, such as beam damage or detection limits, and practical advices to improve experiments. An updated review of biomedical studies involving XAS published over the last 5 years is then provided, paying special attention to metal-based drug biotransformation, metal and nanoparticle toxicology, and element speciation in cancer, neurological, and general pathophysiology. Finally, trends and future developments such as hyphenated methods, in situ correlative imaging and speciation, in vivo X-ray Absorption Near Edge Spectroscopy (XANES), full-field XANES, and X-ray Free Electron Laser (XFEL) XAS are presented. [ABSTRACT FROM AUTHOR]

Relevant events during protein function such as ligand binding/release and interaction with substrates or with light are often accompanied by out-of-equilibrium structural dynamics. Time-resolved experimental techniques have been developed to follow protein structural changes as they happen in real time after a given reaction-triggering event. Time-resolved X-ray solution scattering is a promising approach that bears structural sensitivity with temporal resolution in the femto-to-millisecond time range, depending on the X-ray source characteristics and the triggering method. Here we present the basic principles of the technique together with a description of the most relevant results recently published and a discussion on the computational methods currently developed to achieve a structural interpretation of the time-resolved X-ray solution scattering experimental data. [Display omitted] [ABSTRACT FROM AUTHOR]

The present article is devoted to the radiation from the electron bunch with modulated density passes through the stack consisting of two plates with different thicknesses and electrodynamic properties. The new elegant expression for the frequency-angular distribution of transition radiation is obtained. Using the existence of resonant frequency at which the longitudinal form-factor of bunch not suppresses radiation coherence and choosing parameters for the stack of plates, one can also avoid suppression of the radiation coherence by transverse form-factor of bunch. The radiation from a bunch with modulated density in the process SASE (self-amplified spontaneous emission) FEL can be partially coherent at a resonant frequency. Then the intense sub monochromatic beam of X-ray photons is formed. On the other hand one can define an important parameter of the bunch density modulation depth which is unknown to this day. [ABSTRACT FROM AUTHOR]

It is important to precisely set and keep the phase and amplitude of an rf signal in the accelerating cavity of modern accelerators, such as an X-ray Free Electron Laser (XFEL) linac. In these accelerators an acceleration rf signal is generated or detected by an In-phase and Quadrature (IQ) modulator, or a demodulator. If there are any deviations of the phase and the amplitude from the ideal values, crosstalk between the phase and the amplitude of the output signal of the IQ modulator or the demodulator arises. This causes instability of the feedback controls that simultaneously stabilize both the rf phase and the amplitude. To compensate for such deviations, we developed a novel compensation method using a two-dimensional Discrete Fourier Transform (DFT). Because the observed deviations of the phase and amplitude of an IQ modulator involve sinusoidal and polynomial behaviors on the phase angle and the amplitude of the rf vector, respectively, the DFT calculation with these basis functions makes a good approximation with a small number of compensation coefficients. Also, we can suppress high-frequency noise components arising when we measure the deviation data. These characteristics have advantages compared to a Look Up Table (LUT) compensation method. The LUT method usually demands many compensation elements, such as about 300, that are not easy to treat. We applied the DFT compensation method to the output rf signal of a C-band IQ modulator at SACLA, which is an XFEL facility in Japan. The amplitude deviation of the IQ modulator after the DFT compensation was reduced from 15.0% at the peak to less than 0.2% at the peak for an amplitude control range of from 0.1 V to 0.9 V (1.0 V full scale) and for a phase control range from 0 degree to 360 degrees. The number of compensation coefficients is 60, which is smaller than that of the LUT method, and is easy to treat and maintain. [ABSTRACT FROM AUTHOR]

Electron–positron pair production by the Breit–Wheeler process embedded in a strong laser pulse is analyzed. The transverse momentum spectrum displays prominent peaks which are interpreted as caustics, the positions of which are accessible by the stationary phases. Examples are given for the superposition of an XFEL beam with an optical high-intensity laser beam. Such a configuration is available, e.g., at LCLS at present and at European XFEL in near future. It requires a counter propagating probe photon beam with high energy which can be generated by synchronized inverse Compton backscattering. [ABSTRACT FROM AUTHOR]

The new free-electron lasers (FELs) open up new possibilities for the study of biological particles such as proteins and viruses. Development of new data analysis algorithms requires large datasets of diffraction images produced by simulation. Existing programs are not capable of effective use of modern computational resources, and especially not adapted to the hybrid architecture with GPU. We explored the possibility of performance increase in the SPSIM program for simulation of large datasets of diffraction images, using CUDA technology. Also, we have implemented new capabilities in simulation of FEL experiments special features. [ABSTRACT FROM AUTHOR]

We provide a simple physical picture of the molecular frame photoelectron angular distributions (MFPAD). In the energy region near the ionization threshold, it has been demonstrated that the MFPAD can be understood by the interference between several partial waves. In the energy region higher than 100 eV, the MFPAD has been interpreted by the intra-molecule photoelectron diffraction. That is, it has been verified that multiple-scattering X-ray photoelectron diffraction (XPD) theory is a promising probe of the dynamical process. Therefore, we look into the future: a new methodology for molecular structure determination will be applied to determine ultrafast molecular structure changes due to ultrafast core-level XPD imaging from within, as demonstrated in our simulations for elemental processes of photo-induced unimolecular reactions. [ABSTRACT FROM AUTHOR]

We have investigated the effects of X-ray irradiation to doses of 0, 200 Gy, 20 kGy, 2 MGy, and 20 MGy on the Hamamatsu silicon-photomultiplier (SiPM) S10362-11-050C. The SiPMs were irradiated without applied bias voltage. From current-voltage, capacitance/conductance-voltage, capacitance/conductance-frequency, pulse-shape, and pulse-area measurements, the SiPM characteristics below and above breakdown voltage were determined. Significant changes of some SiPM parameters are observed. Up to a dose of 20 kGy the performance of the SiPMs is hardly affected by X-ray radiation damage. For doses of 2 and 20 MGy the SiPMs operate with hardly any change in gain, but with a significant increase in dark-count rate and cross-talk probability. [ABSTRACT FROM AUTHOR]

The most common applications of diamond crystals in X-ray optics are high-heat-load monochromators for synchrotron beamlines and phase retarders for polarization control. Here, less common applications of diamond at the frontier of X-ray crystal optics are reviewed and summarized. These include a sub-meV-bandwidth X-ray monochromator with high spectral efficiency [1] and all-diamond optical assemblies for a beam-multiplexing double-crystal monochromator at the Linac Coherent Light Source [2]. Also, novel applications for the realization of fully coherent hard X-ray sources are discussed, such as, diamond crystal optics for self-seeding of hard X-rays in the Linac Coherent Light Source [3,4] and Bragg mirrors for the highly anticipated X-ray free-electron laser oscillator [5,6]. These examples present diamond as a material for the next generation of X-ray optics, optics which can provide unique characteristics and capabilities to modern X-ray sources. In addition, details of practical importance on fabrication and characterization methods of diamond crystals with the suitable quality are presented. [ABSTRACT FROM AUTHOR]

Abstract: The field of Membrane Protein Structural Biology has grown significantly since its first landmark in 1985 with the first three-dimensional atomic resolution structure of a membrane protein. Nearly twenty-six years later, the crystal structure of the beta2 adrenergic receptor in complex with G protein has contributed to another landmark in the field leading to the 2012 Nobel Prize in Chemistry. At present, more than 350 unique membrane protein structures solved by X-ray crystallography (http://blanco.biomol.uci.edu/mpstruc/exp/list, Stephen White Lab at UC Irvine) are available in the Protein Data Bank. The advent of genomics and proteomics initiatives combined with high-throughput technologies, such as automation, miniaturization, integration and third-generation synchrotrons, has enhanced membrane protein structure determination rate. X-ray crystallography is still the only method capable of providing detailed information on how ligands, cofactors, and ions interact with proteins, and is therefore a powerful tool in biochemistry and drug discovery. Yet the growth of membrane protein crystals suitable for X-ray diffraction studies amazingly remains a fine art and a major bottleneck in the field. It is often necessary to apply as many innovative approaches as possible. In this review we draw attention to the latest methods and strategies for the production of suitable crystals for membrane protein structure determination. In addition we also highlight the impact that third-generation synchrotron radiation has made in the field, summarizing the latest strategies used at synchrotron beamlines for screening and data collection from such demanding crystals. This article is part of a Special Issue entitled: Structural and biophysical characterisation of membrane protein-ligand binding. [Copyright &y& Elsevier]

Abstract: The high intensity and high repetition rate of the European X-Ray Free-Electron Laser, presently under construction in Hamburg, will require pixel sensors which can stand X-ray doses up to 1GGy for 3years of operation. Within the AGIPD Collaboration the Hamburg group has systematically studied X-ray damage in silicon sensors for the dose range between 1kGy and 1GGy using strip sensors and test structures fabricated on high-ohmic n-type silicon from four different vendors. The densities of oxide charges, interface traps and surface current as function of dose and annealing conditions have been determined. The results have been implemented in TCAD simulations, and the radiation performance of strip sensors and guard-ring structures has been simulated and compared to experimental results. Finally, with the help of detailed TCAD simulations, the layout and technological parameters of the AGIPD pixel sensor have been optimized. It is found that the optimization for silicon sensors exposed to high X-ray doses is significantly different from that for non-irradiated sensors, and that the specifications of the AGIPD sensor can be met. [Copyright &y& Elsevier]

Abstract: The AGIPD (Adaptive Gain Integrating Pixel Detector) is a detector under development, to be used in the European X-ray Free-Electron Laser (XFEL). The constraints imposed by the XFEL source are discussed, and the solutions implemented to cope with them are explained. The present status of the project is reported, along with results achieved in terms of noise, memory depth, and radiation tolerance. [Copyright &y& Elsevier]

Abstract: A systematic experimental study of the main challenges for silicon-pixel sensors at the European XFEL is presented. The high instantaneous density of X-rays and the high repetition rate of the XFEL pulses result in signal distortions due to the plasma effect and in severe radiation damage. The main parameters of X-ray-radiation damage have been determined and their impact on sensors is investigated. These studies form the basis of the optimized design of a pixel-sensor for experimentation at the European XFEL. [Copyright &y& Elsevier]

Abstract: Using the multi-channel transient current technique the currents induced by electron–hole pairs, produced by a focussed sub-nanosecond laser of 660nm wavelength close to the Si–SiO2 interface of silicon strip sensors have been measured, and the charge-collection efficiency determined. The laser has been operated in burst mode, with bursts typically spaced by 1ms, each consisting of 30 pulses separated by 50ns. In a previous paper it has been reported that, depending on X-ray-radiation damage, biasing history and humidity, situations without charge losses, with hole losses, and with electron losses have been observed. In this paper we show for sensors before and after irradiation by X-rays to 1MGy (SiO2), how the charge losses change with the number of electron–hole pairs generated by each laser pulse, and the time interval between the laser pulses. This allows us to estimate how many additional charges in the accumulation layers at the Si–SiO2 interface have to be trapped to significantly change the local electric field, as well as the time it takes that the accumulation layer and the electric field return to the steady-state situation. In addition, results are presented on the change of the pulse shape caused by the plasma effect for high charge densities deposited close to the Si–SiO2 interface. [Copyright &y& Elsevier]

Abstract: We report design, fabrication, and results of X-ray topography characterization of thin synthetic type IIa diamond crystal plates and crystal-holder assemblies developed for the Hard X-ray Self-Seeding project at the Linac Coherent Light Source. The goal of the project was to achieve generation of fully coherent hard X-rays using the self-seeding concept and the single-crystal diamond wake monochromator [Geloni et al., J. Mod. Opt. 58, 1391 (2011)]. High crystal quality, crystal thickness of ≈0.1–0.2mm and strain-free crystal mount were the main requirements. Nearly defect-free diamond plates of (001) orientation, with thicknesses of 0.1mm and 0.15mm, and of a trapezoidal shape were fabricated and preliminarily evaluated. The plates were further characterized using X-ray topography. These tests helped to minimize strain in crystals induced by mounting in crystal holders and to determine defect-free crystal regions. Self-seeding experiments were conducted at the Linac Coherent Light Source using the diamond plates and crystal-holder assemblies selected by our studies. Fully coherent 8.33-keV X-rays with 5×10−5 relative bandwidth were produced [Amann et al., Nat. Photonics 6, 693 (2012)]. [Copyright &y& Elsevier]

Abstract: We have developed and constructed a C-band (4.760GHz) rf cavity beam position monitor (RF-BPM) system for the XFEL facility at SPring-8, SACLA. The demanded position resolution of the RF-BPM is less than , because an electron beam and x-rays must be overlapped within precision in the undulator section for sufficient FEL interaction between the electrons and x-rays. In total, 57 RF-BPMs, including IQ demodulators and high-speed waveform digitizers for signal processing, were produced and installed into SACLA. We evaluated the position resolutions of 20 RF-BPMs in the undulator section by using a 7GeV electron beam having a 0.1nC bunch charge. The position resolution was measured to be less than , which was sufficient for the XFEL lasing in the wavelength region of 0.1nm, or shorter. [Copyright &y& Elsevier]

Abstract: Recently, much attention has been devoted to the development of new pulsed sources of radiation for investigating matter with atomic scale temporal and spatial resolution. While much has been achieved thanks to modern ultrafast laser technology, the ultimate coherent light source, the X-ray free electron laser (X-FEL), promises to deliver the highest X-ray photon flux in the shortest pulses at energies unreachable by conventional solid-state lasers. In parallel, other approaches that utilize electrons in table-top setups as a probe have been developed demonstrating the potential for a valid complement to X-ray based techniques. Here, we consider yet another possible avenue in which the technology of electron diffraction and imaging is pushed further; we estimate the interest and performances of a femtosecond high energy electron microscope and propose a hybrid experiment with relativistic electrons as a probe and fs X-ray pulses as a pump taking advantage of both technologies. [Copyright &y& Elsevier]

Abstract: We propose an experimental setup allowing for measurement of the whole diffraction curve of a Bragg peak by single pulse exposure where a bended sample is illuminated by a set of parallel pencil beams under locally different angles of incidence. The feasibility is demonstrated probing the 1st order Bragg peak of Ru/B4C multilayers for photon energies close to Boron K-edge. The evaluated optical parameters recorded from bent sample under fixed sample setting equals those obtained from a flat sample using angular dispersive recording. Subsequently our scheme is appropriate for solid state experiment using at high intense femtosecond pulses provided by free-electron laser sources. [Copyright &y& Elsevier]

Abstract: A pixel-level 8-bit 5-MS/s digitizer for the DSSC X-ray imager utilizing the method of Wilkinson is presented. The timing information is generated column-wise by means of an 8-bit Gray-code counter. The 625-ps time stamps are distributed to the column pixels through 13-mm long shielded coplanar waveguides. Pixel-internal blocks comprise a sample-and-hold stage with current source for ramp generation, a temperature-compensated and supply voltage-stabilized reference circuitry, a comparator, a bank of eight receivers with latches for the time stamps, and control logic. These pixel-internal and global devices in 130-nm CMOS technology occupy 0.015 and 0.012mm2, respectively. The power consumption amounts to at 1.2-V supply voltage. Taking the 0.8-V dynamic range into account, the simulated rms-noise voltage of about corresponds to a signal-to-noise ratio above 70dB. The differential and integral nonlinearity is expected to remain below 0.4 LSB and 1 LSB, respectively. All results promise the compliance with underlying requirements. [ABSTRACT FROM AUTHOR]

Abstract: A new DEPFET detector-amplifier structure with strongly non-linear characteristics is presented. It will be used as basic element of an X-ray pixel detector at the new XFEL free electron laser radiation source to be constructed in Hamburg, Germany, providing at the same time single X-ray photon detection and high dynamic range even when operated at readout frequency up to 5MHz. This is possible due to the new detector concept that adds to the excellent DEPFET properties – combined function of detector amplifier and data storage, full sensitivity over whole bulk, non-destructive readout, low serial noise and absence of reset noise – the new features of very large charge handling capability and signal compression. Concept and design will be presented and properties demonstrated by extended computer simulations. [ABSTRACT FROM AUTHOR]

Abstract: The new DSSC (DEPFET sensor with signal compression) detector system is being developed in order to fulfil the requirements of the future XFEL in Hamburg. The instrument will be able to record X-ray images with a maximum frame rate of 5MHz and to achieve a high dynamic range. The system is based on a silicon pixel sensor with a new designed non-linear-DEPFET as a central amplifier structure. The detector chip is bump-bonded to mixed signal readout ASICs that provide full parallel readout and temporary data storage. The signals coming from the detector are processed by an analog filter, immediately digitized by 8-ENOB ADCs and locally stored in a custom designed memory. The ASICs are designed in 130nm CMOS technology. During the time gap of 99ms of the XFEL machine, the digital data are sent off the focal plane to a DAQ electronics that acts as an interface to the back-end of the whole instrument. The pixel sensor has been designed so as to combine high energy resolution at low signal charge with high dynamic range. This has been motivated by the desire to be able to be sensitive to single low energy photons and, at the same time, to measure at other positions of the detector signals corresponding to up to 104 photons of 1keV. In order to fit this dynamic range into a reasonable output signal swing, achieving at the same time single photon resolution, a strongly non-linear characteristic is required. The new proposed DEPFET provides the required dynamic range compression at the sensor level, considerably facilitating the task of the electronics. At the same time the DEPFET charge handling capacitance is enormously increased with respect to standard DEPFETs. The sensor matrix will comprise pixels of hexagonal shape with a side-length of . The simultaneous implementation of the 5MHz frame rate, of the single low-energy photon resolution and of the high dynamic range goes beyond all the existing instruments and requires the development of new concepts and technologies. [Copyright &y& Elsevier]

Abstract: In this paper, we propose a novel architecture to implement the current readout of DePFET Active Pixel Sensor (APS) matrices to be used in experiments at the European X-ray Free Electron Laser (XFEL). The circuit performs a fast trapezoidal filtering of the DePFET signal with a very simple architecture based on a Flip Capacitor Filter solution. We discuss the possible available trade-offs between noise and speed performances based on three different timing strategies that can be used to readout the DePFET matrix. Simulation results are shown for a first design of the circuit and expected noise performances are discussed in the last part of the paper. [ABSTRACT FROM AUTHOR]

Abstract: Zone plates are high quality optics that have the potential to provide diffraction-limited nano-focusing of hard X-ray free electron laser radiation. The present publication investigates theoretically the temperature behavior of metal zone plates on a diamond substrate irradiated by 0.1nm X-rays from the European X-ray Free Electron Laser. The heat transfer in the optic is simulated by solving the transient heat equation with the finite element method. Two different zone plate designs are considered, one small zone plate placed in the direct beam and one larger zone plate after the monochromator. The main result is that for all investigated cases the maximum temperature in the metal zone plate layer is at least a factor 2 below the melting point of the respective material, proving the efficiency of the proposed cooling scheme. However, zone plates in the direct beam experience large and rapid temperature fluctuations of several hundred Kelvin that might prove fatal to the optic. The situation is different for optics behind the monochromator with fluctuations in the 20K range and maximum temperatures well below room temperature. The simulation results give valuable indications on the temperature behavior to be expected and are a basis for future experimental heat transfer and mechanical stability investigations of fabricated nanostructures. [ABSTRACT FROM AUTHOR]

Abstract: The impact of electron hole plasmas on silicon sensor performance was studied with a multi-channel Transient Current Technique (mTCT) setup. Electron hole densities of up to 1016 cm−3 (equivalent to 105 focused 12keV photons) were created with sub-ns lasers (660 and 1015nm) and the time resolved current pulses of segmented sensors (4 channels simultaneously) were read out by a 2.5GHz oscilloscope. Measurements for strip sensors of thickness and pitch as well as thickness and pitch were carried out showing an increase of the charge collection time and an increase of the charge spread (charge cloud explosion) with increased charge carrier density. These effects were studied as a function of the applied bias voltage and electron hole density. It was shown that for the current AGIPD sensor design plasma effects in p-in-n sensors of thickness are negligible if at least 500V bias is applied. [Copyright &y& Elsevier]

Abstract: A system-level model of a low-noise high-speed mega-pixel camera with gain compression for X-ray photon correlation spectroscopy experiments at the European XFEL is presented. The model comprises the full signal chain from the sensor element via amplifier/filter and digitizer to the memory. The influence of gain- and offset errors as well as noise on the experiment-relevant image fidelity and intensity correlation function is discussed and compensation techniques are developed. A case study demonstrates the achievable efficiency of the chosen system parameters. [Copyright &y& Elsevier]

Abstract: Instead of using a helical undulator, another method to generate circularly polarized radiation in an FEL is to utilize two crossed planar undulators. The main benefit of the crossed undulator over the helical option is that its structure is simpler so that it is technically and economically more convenient. Unlike a helical undulator, two orthogonal polarizations are respectively generated from two crossed undulators and their combination comprises circularly polarized radiation. Therefore, the overlap and resemblance of the two polarizations determine the quality of the composed radiation field. The 3D simulations have been performed with parameters from the European XFEL. Polarization has been studied in detail and optimization of the crossed undulator length has also been done. [Copyright &y& Elsevier]

This work presents the design of an interleaved Successive Approximation Register (SAR) ADC, part of the readout channel for the PixFEL detector. The PixFEL project aims at substantially advancing the state-of-the-art in the field of 2D X-ray imaging for applications at the next generation Free Electron Laser (FEL) facilities. For this purpose, the collaboration is developing the fundamental microelectronic building blocks for the readout channel. This work focuses on the design of the ADC carried out in a 65 nm CMOS technology. To obtain a good tradeoff between power consumption, conversion speed and area occupation, an interleaved SAR ADC architecture was adopted. [ABSTRACT FROM AUTHOR]

Abstract: Future 4th generation photon sources, such as the European XFEL based in Hamburg, will deliver around X-ray photons in less than 100fs with full lateral coherence. These new sources will offer unprecedented possibilities in photon science. The high peak brilliance, combined with a 5MHz repetition rate poses very high demands for the 2D detectors. In order to provide appropriate detectors during XFEL startup, three dedicated development projects have been initiated, one of them being the Adaptive Gain Integrating Pixel Detector (AGIPD) project which is a collaborative effort between DESY, PSI, University of Bonn, and University of Hamburg. An essential part of the AGIPD project is the development of a simulation tool for the complete detection system. The simulation tool as well as preliminary simulations of the detector characteristics is presented. [Copyright &y& Elsevier]

Abstract: On 27 April 2006 a vacuum ultra violet free electron laser (FEL) named free electron laser in Hamburg (FLASH) producing intense beams of 13.1nm laser light became operational. A 260m long, 1GeV superconducting electron linear accelerator (linac) drives the FLASH. The electron linac is made of an array of superconducting niobium cavities developed at DESY on TESLA technology. During the FEL operation a parasitic radiation field of photoneutrons and bremsstrahlung gamma rays persists in the linac containment tunnel. Sophisticated measurement and control devices, based on radiation-sensitive commercial off the shelf (COTS) microelectronic components, have been installed near the FLASH linac. Therefore, it becomes necessary to characterise these stray radiations, in order to predict the radiation effects on electronics. This paper summarises the features of novel radiation dosimeters and accelerator dosimetry techniques developed by our group. The utilisation of valuable radiation dosimetry data gathered from the experiments at FLASH to predict the radiation field characteristics of the future European X-ray free electron laser (XFEL) driven by a 20GeV superconducting electron linac is highlighted. [Copyright &y& Elsevier]

Abstract: We present a theoretical study of the feasibility of surface scattering experiments with X-ray photon correlation spectroscopy at the planned X-ray free electron laser (XFEL). We are calculating scattering cross sections, count rates, signal to noise ratios and time scales of capillary waves on liquid water, liquid mercury and liquid glycerol at nanometer length scales. The use of an X-ray delay line to produce arbitrary lagtimes in the correlation spectroscopy is discussed and demonstrated with the example of surface scattering. Estimates of sample heating during the intense XFEL pulse are given. [Copyright &y& Elsevier]

Abstract: In this paper, we describe the layout of the bunch compressor for the Beijing XFEL test facility (BTF). Our bunch compressor setup is different from the usual one due to the space limit. The compensation X-BAND cavity and the first bunch compressor are separate in distance. The electron bunch is decelerated first and then accelerated to enter the first bunch compressor. The simulation result shows that our setup works well, and the nonlinear term is well compensated. Also, we present the result about the CSR emittance dilution study. Finally, we develop a program to study microbunch instability in the second BTF bunch compressor. [Copyright &y& Elsevier]

• X-ray pulse intensity influence on hydrogen ion degradation is considered. • Trajectory method is applied to study object degradation. • Results for different hydrogen ion internuclear distances. are compared The drastic evolution of molecular systems exposed to ultrashort intense X-ray pulse is a fundamental obstacle for single-particle imaging (SPI) by means of X-ray free electron lasers (XFEL). Here we tackle the simplest molecule H 2 + and its diffraction pattern degradations in the strong ultrashort X-ray beam. The semiclassical method of the problem solution and its advantages are described in detail. We apply the method to calculate the electron density autocorrelation functions (ACF) for a few internuclear distances and then discuss numeric simulation data. [ABSTRACT FROM AUTHOR]

Abstract: For experiments at the European X-ray Free-Electron Laser (XFEL) the Adaptive Gain Integrating Pixel Detector (AGIPD) is under development. The particular requirements for the detector are a high dynamic range of 0, 1 to more than 104 12.4keV photons per pixel for an XFEL pulse duration of , and a radiation tolerance of 1GGy. The nominal operating voltage is 500V, however for special applications an operation close to 1000V should be possible. Experimental data on the dose dependence of the oxide-charge density at the Si–SiO2 interface and the surface-current density have been used in TCAD simulations and the layout of the pixels and guard-rings optimized. Finally the expected performance, in particular breakdown voltage, dark current and inter-pixel capacitance as function of X-ray dose are given. [Copyright &y& Elsevier]

Abstract: X-ray free electron lasers (XFELs) promise to revolutionize X-ray science with extremely high peak brilliances and femtosecond X-ray pulses. This will require novel detectors to fully realize the potential of these new sources. There are many current detector development projects aimed at the many challenges of meeting the XFEL requirements . This paper describes a pixel array detector (PAD) that has been developed for the Coherent X-ray Imaging experiment at the Linac Coherent Light Source (LCLS) at the SLAC National Laboratory . The detector features 14-bit in-pixel digitization; a 2-level in-pixel gain setting that can be used to make an arbitrary 2-D gain pattern that is adaptable to a particular experiment; the ability to handle instantaneous X-ray flux rates of 1017 photons per second; and continuous frames rates in excess of 120Hz. The detector uses direct detection of X-rays in a silicon diode. The charge produced by the diode is integrated in a pixilated application specific integrated circuit (ASIC) which digitizes collected holes with single X-ray photon capability. Each ASIC is 194×185 pixels, each pixel is on a side. Each pixel can detect up to 2500 X-rays per frame in low-gain mode, yet easily detects single photons at high-gain. Cooled, single-chip detectors have been built and meet all the required specifications. SLAC National Laboratory is engaged in constructing a tiled, multi-chip 1516×1516 pixel detector. [Copyright &y& Elsevier]

Abstract: This work will show the investigation into a possible design of flat panel geometry for the large pixel detector (LPD) at the X-ray free electron laser (XFEL) at DESY. LPD will be one of the detections systems for applications such as coherent X-ray diffraction imaging, small molecule imaging and pump-probe techniques. A proposed design of the LPD is to incorporate edgeless technology through the use of current terminating ring structures. Additionally dry-etching techniques to minimize the edge effects associated with tiled detectors are also examined. [Copyright &y& Elsevier]

Abstract: The European X-ray free electron laser is a new research facility currently under construction in Hamburg, Germany. Typical for XFEL machines is the high peak brilliance several orders of magnitudes above existing synchrotron facilities. With a pulse length below 100fs and an extremely high luminosity of 30,000 flashes per second the European XFEL will have a worldwide unique time structure that enables researchers to record movies of ultrafast processes. This demands the development of new detectors tailored to the requirements imposed by the experiments while complying with the machine specific operation parameters. The adaptive gain integrating pixel detector (AGIPD) is one response to the need for large 2D detectors, able to cope with the 5MHz repetition rate, as well as with the high dynamic range needed by XFEL experiments (from single photons to 104 12keV photons per pixel per pulse). In addition, doses up to 1GGy over three years are expected. [Copyright &y& Elsevier]