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Physical review letters 108, 5 (2012). doi:10.1103/PhysRevLett.108.245005, Published by APS, College Park, Md.

We are designing and building the next generation multi-purpose instrumentation especially adapted to accommodate unique large-area, single-photon counting pnCCD detectors together with advanced many-particle ion and electron imaging spectrometers (reaction microscope, REMI; velocity map imaging, VMI; magnetic bottle) for simultaneous detection of scattered and fluorescent photons and charged particles in experiments at the LCLS FEL.

We demonstrate the use of an X-ray free electron laser synchronized with an optical pump laser to obtain X-ray diffraction snapshots from the photoactivated states of large membrane protein complexes in the form of nanocrystals flowing in a liquid jet. Light-induced changes of Photosystem I-Ferredoxin co-crystals were observed at time delays of 5 to 10 µs after excitation. The result correlates with the microsecond kinetics of electron transfer from Photosystem I to ferredoxin. The undocking process that follows the electron transfer leads to large rearrangements in the crystals that will terminally lead to the disintegration of the crystals. We describe the experimental setup and obtain the first time-resolved femtosecond serial X-ray crystallography results from an irreversible photo-chemical reaction at the Linac Coherent Light Source. This technique opens the door to time-resolved structural studies of reaction dynamics in biological systems.

X-ray free electron laser (X-FEL)-based serial femtosecond crystallography is an emerging method with potential to rapidly advance the challenging field of membrane protein structural biology. Here we recorded interpretable diffraction data from micrometer-sized lipidic sponge phase crystals of the Blastochloris viridis photosynthetic reaction center delivered into an X-FEL beam using a sponge phase micro-jet.

Resonant x-ray emission spectroscopy with short x-ray pulses from the Linac Coherent Light Source (LCLS) was used to probe the nonequilibrium electron dynamics in highly excited polar semiconductors. In these materials, transient surface-space-charge field screening by the photoexcited carriers (electrons and holes) is expected to launch coherent longitudinal optical phonons which, as a result of the Coulomb coupling between the ionic-atoms and the photoexcited electrons, mix to new coupled phonon-plasmon modes. By tuning the LCLS photon energy to drive a transition between a core level and the conduction band, we observe picosecond (ps) and sub-ps changes on the emission intensity caused by the redistribution and relaxation of the conduction band electrons in the presence of such phonon-plasmon modes. These time dependent changes of the emission intensity reflect directly the evolution of the non-equilibrium electron distribution function.

A crystal of hen egg-white lysozyme was analyzed by means of energy-dispersive X-ray Laue diffraction with white synchrotron radiation at 2.7 Å resolution using a pnCCD detector. From Laue spots measured in a single exposure of the arbitrarily oriented crystal, the lattice constants of the tetragonal unit cell could be extracted with an accuracy of about 2.5%. Scanning across the sample surface, Laue images with split reflections were recorded at various positions. The corresponding diffraction patterns were generated by two crystalline domains with a tilt of about 1° relative to each other. The obtained results demonstrate the potential of the pnCCD for fast X-ray screening of crystals of macromolecules or proteins prior to conventional X-ray structure analysis. The described experiment can be automatized to quantitatively characterize imperfect single crystals or polycrystals.

X-ray free-electron lasers deliver intense femtosecond pulses that promise to yield high resolution diffraction data of nanocrystals before the destruction of the sample by radiation damage. Diffraction intensities of lysozyme nanocrystals collected at the Linac Coherent Light Source using 2 keV photons were used for structure determination by molecular replacement and analyzed for radiation damage as a function of pulse length and fluence. Signatures of radiation damage are observed for pulses as short as 70 fs. Parametric scaling used in conventional crystallography does not account for the observed effects.

X-ray free-electron lasers have enabled new approaches to the structural determination of protein crystals that are too small or radiation-sensitive for conventional analysis1. For sufficiently short pulses, diffraction is collected before significant changes occur to the sample, and it has been predicted that pulses as short as 10 fs may be required to acquire atomic-resolution structural information1, 2, 3, 4. Here, we describe a mechanism unique to ultrafast, ultra-intense X-ray experiments that allows structural information to be collected from crystalline samples using high radiation doses without the requirement for the pulse to terminate before the onset of sample damage. Instead, the diffracted X-rays are gated by a rapid loss of crystalline periodicity, producing apparent pulse lengths significantly shorter than the duration of the incident pulse. The shortest apparent pulse lengths occur at the highest resolution, and our measurements indicate that current X-ray free-electron laser technology5 should enable structural determination from submicrometre protein crystals with atomic resolution.

Single-particle experiments using X-ray Free Electron Lasers produce more than 10(5) snapshots per hour, consisting of an admixture of blank shots (no particle intercepted), and exposures of one or more particles. Experimental data sets also often contain unintentional contamination with different species. We present an unsupervised method able to sort experimental snapshots without recourse to templates, specific noise models, or user-directed learning. The results show 90% agreement with manual classification.

Subfemtosecond bursts of extreme ultraviolet radiation, facilitated by a process known as high-order harmonic generation, are a key ingredient for attosecond metrology, providing a tool to precisely initiate and probe ultrafast dynamics in the microcosms of atoms, molecules, and solids. These ultrashort pulses are always, and as a by-product of the way they are generated, accompanied by laser-induced recollisions of electrons with their parent ions. By using a few-cycle infrared (${\ensuremath{\lambda}}_{0}=2.1\text{ }\text{ }\ensuremath{\mu}\mathrm{m}$) driving laser, we were able to directly excite high-energy ($\ensuremath{\sim}870\text{ }\text{ }\mathrm{eV}$) inner-shell electrons through laser-induced electron recollision, opening the door to time-resolved studies of core-level and concomitant multielectron dynamics.

VERITAS is the first 128-channel ASIC developed to readout both the pnCCDs and the DEPFET arrays produced at the MPI-Halbleiterlabor in Munich. These detectors are used in a large variety of scientific applications, ranging from X-ray astronomy to the new X-ray Free Electron Laser sources. The main concept of VERITAS is to provide a flexible readout chip able to cope not only with different kinds of detectors, but also with a large set of operating conditions that may require very different noise thresholds and input dynamic ranges. These can vary by more than two orders of magnitude. Every analog channel of VERITAS provides trapezoidal weighting function. This filtering strategy had never been applied to the pnCCD before. The very first measurements obtained coupling VERITAS with a 128×256 pnCCD are shown. With these settings an input charge up to 2.5×105 electrons can be processed. With a readout time of 4 µs/line a noise of 3.9 electrons has been measured in the highest gain mode. The resolution obtained on the Mn-Kα peak of a 55Fe source is of 136 eV for single events. A noise of 30 electrons has been achieved in the lowest gain mode at a speed of 6.4 µs/line. In this low gain setting an input charge up to 2.5×105 electrons can be processed. These striking results fulfill the requirements of the main foreseen applications of large-size pnCCDs: experiments with Free Electron Lasers and high-speed optical astronomy. In order to further improve the performance and the flexibility of the ASIC, a second version based on a fully differential architecture has been designed. This topology allows a simpler filter implementation and it is less sensitive to cross-talk. In addition it offers the possibility to switch with the same ASIC between the source follower and drain current readout of the DEPFET sensors. The drain readout should make it possible to reach a processing time of about 2–3 µs/line with an electronics noise ≤10 el. This makes the second version of VERITAS very attractive for the proposed ESA X-ray astronomy mission ATHENA.

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 4th 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.

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.

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 60cm 2 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.

Typical time-scale for excited inner-shell processes is in the range between few femtosecond to sub-femtosecond. Here we present a tool to excite such processes with sub-femtosecond time resolution, enable time-domain studies of these processes.

X-ray crystallography provides the vast majority of macromolecular structures, but the success of the method relies on growing crystals of sufficient size. In conventional measurements, the necessary increase in X-ray dose to record data from crystals that are too small leads to extensive damage before a diffraction signal can be recorded(1-3). It is particularly challenging to obtain large, well-diffracting crystals of membrane proteins, for which fewer than 300 unique structures have been determined despite their importance in all living cells. Here we present a method for structure determination where single-crystal X-ray diffraction 'snapshots' are collected from a fully hydrated stream of nanocrystals using femtosecond pulses from a hard-X-ray free-electron laser, the Linac Coherent Light Source(4). We prove this concept with nanocrystals of photosystem I, one of the largest membrane protein complexes(5). More than 3,000,000 diffraction patterns were collected in this study, and a three-dimensional data set was assembled from individual photosystem I nanocrystals (similar to 200 nm to 2 mm in size). We mitigate the problem of radiation damage in crystallography by using pulses briefer than the timescale of most damage processes(6). This offers a new approach to structure determination of macromolecules that do not yield crystals of sufficient size for studies using conventional radiation sources or are particularly sensitive to radiation damage.

The start-up of the Linac Coherent Light Source (LCLS), the new femtosecond hard X-ray laser facility in Stanford, California, has brought high expectations of a new era for biological imaging. The intense, ultrashort X-ray pulses allow diffraction imaging of small structures before radiation damage occurs. Two papers in this issue of Nature present proof-of-concept experiments showing the LCLS in action. Chapman et al. tackle structure determination from nanocrystals of macromolecules that cannot be grown in large crystals. They obtain more than three million diffraction patterns from a stream of nanocrystals of the membrane protein photosystem I, and assemble a three-dimensional data set for this protein. Seibert et al. obtain images of a non-crystalline biological sample, mimivirus, by injecting a beam of cooled mimivirus particles into the X-ray beam. The start-up of the new femtosecond hard X-ray laser facility in Stanford, the Linac Coherent Light Source, has brought high expectations for a new era for biological imaging. The intense, ultrashort X-ray pulses allow diffraction imaging of small structures before radiation damage occurs. This new capability is tested for the problem of imaging a non-crystalline biological sample. Images of mimivirus are obtained, the largest known virus with a total diameter of about 0.75 micrometres, by injecting a beam of cooled mimivirus particles into the X-ray beam. The measurements indicate no damage during imaging and prove the concept of this imaging technique. X-ray lasers offer new capabilities in understanding the structure of biological systems, complex materials and matter under extreme conditions1,2,3,4. Very short and extremely bright, coherent X-ray pulses can be used to outrun key damage processes and obtain a single diffraction pattern from a large macromolecule, a virus or a cell before the sample explodes and turns into plasma1. The continuous diffraction pattern of non-crystalline objects permits oversampling and direct phase retrieval2. Here we show that high-quality diffraction data can be obtained with a single X-ray pulse from a non-crystalline biological sample, a single mimivirus particle, which was injected into the pulsed beam of a hard-X-ray free-electron laser, the Linac Coherent Light Source5. Calculations indicate that the energy deposited into the virus by the pulse heated the particle to over 100,000 K after the pulse had left the sample. The reconstructed exit wavefront (image) yielded 32-nm full-period resolution in a single exposure and showed no measurable damage. The reconstruction indicates inhomogeneous arrangement of dense material inside the virion. We expect that significantly higher resolutions will be achieved in such experiments with shorter and brighter photon pulses focused to a smaller area. The resolution in such experiments can be further extended for samples available in multiple identical copies.

A PNCCD is successfully operating as one of the focal plane CCDs aboard the satellite XMM-Newton. An advanced version of this kind of CCDs will be the sensing devices for the eROSITA X-ray astronomy mission. These fully depleted CCDs are developed and manufactured at the MaxPlanck-Institute Semiconductor Lab together with the company PNSensor. Their performance features make them useful in a variety of measurement situations in addition to the astronomical ones. Applications range from photon detection (e.g. optical wave front sensors, cameras for X-ray free electron lasers) to charged particle detection of e.g. electrons, protons, and alpha particles. First tests have been performed for using a PNCCD in a transmission electron microscope (TEM). Alpha particles of an 241Am radioactive source are used for generating large signal electron clouds for diagnostic purposes. Finally, protons have been used in a radiation hardness test. These three applications will be described and discussed. The prospect of resolving space and energy of each particle in combination with ∼100% efficiency makes the PNCCD especially suitable for low flux applications e.g. examining sensitive samples in a TEM.

We exploited the possibility of using a pulsed mono-energetic proton beam — coming from the DEFEL beam-line of the Tandetron accelerator at LaBEC (Laboratorio di Tecniche Nucleari per i Beni Culturali) in Sesto Fiorentino, Italy — as a diagnostic tool for the characterization of the response of semiconductor detectors at high charge densities. In fact accelerated protons owing to their limited range in silicon can deliver a large and precisely calibrated amount of charge along a track well matched to the typical silicon wafer thickness. As a case study we considered the characterization at high level of charge injection of a Multi-Linear Silicon Drift Detector prototype for position-sensing applications. The focus is on the potentiality of the experimental technique and on the first results of the experimental characterization of the detector.

The human population is getting older and older, as stated by current studies. Because elderly people are at a higher risk of in house accidents there is an increasing need for ambient assisted living systems. These systems should detect accidents or dangerous situations in order to improve the quality of life for these people. The goal of this work is to build a robust and intelligent system which estimates the position of humans using only one camera. The position is used to detect falls and to allow an immediate call for help. The solution is based on a foreground-background-segmentation using Gaussian Mixture Models to first detect people and than analyze their main and ideal orientation using moments. This allows to decide whether a person is staying or lying on the floor. The system has a low latency and a detection rate of 88% in our case study.

For the eROSITA X-ray telescope, which is planned to be launched in 2012, detectors were developed and fabricated at the MPI Semiconductor Laboratory. The fully depleted, back-illuminated pnCCDs have an ultrathin pn-junction to improve the low-energy X-ray response function and quantum efficiency. The device thickness of 450 μm is fully sensitive to X-ray photons yielding high quantum efficiency of more than 90% at photon energies of 10 keV. An on-chip filter is deposited on top of the entrance window to suppress visible and UV light which would interfere with the X-ray observations. The pnCCD type developed for the eROSITA telescope was characterized in terms of quantum efficiency and spectral response function. The described measurements were performed in 2009 at the synchrotron radiation sources BESSY II and MLS as cooperation between the MPI Semiconductor Laboratory and the Physikalisch-Technische Bundesanstalt (PTB). Quantum efficiency measurements over a wide range of photon energies from 3 eV to 11 keV as well as spectral response measurements are presented. For X-ray energies from 3 keV to 10 keV the quantum efficiency of the CCD including on-chip filter is shown to be above 90% with an attenuation of visible light of more than five orders of magnitude. A detector response model is described and compared to the measurements.

This paper presents a complete system to detect scratches in rolls of photo paper. The idea is to use a group of white LED to illuminate the picture and highlight the scratches only. The system mainly consists of a camera to obtain images from the paper and an Altera DE2-70 FPGA Board to process those images. We can show that observing the scratches by applying specific filters on the acquired image makes the detection very simple and reliable.

Fourth generation accelerator-based light sources, such as VUV and X-ray Free Electron Lasers (FEL), deliver ultra-brilliant (∼1012–1013 photons per bunch) coherent radiation in femtosecond (∼10–100 fs) pulses and, thus, require novel focal plane instrumentation in order to fully exploit their unique capabilities. As an additional challenge for detection devices, existing (FLASH, Hamburg) and future FELs (LCLS, Menlo Park; SCSS, Hyogo and the European XFEL, Hamburg) cover a broad range of photon energies from the EUV to the X-ray regime with significantly different bandwidths and pulse structures reaching up to MHz micro-bunch repetition rates. Moreover, hundreds up to trillions of fragment particles, ions, electrons or scattered photons can emerge when a single light flash impinges on matter with intensities up to 1022 W/cm2. In order to meet these challenges, the Max Planck Advanced Study Group (ASG) within the Center for Free Electron Laser Science (CFEL) has designed the CFEL-ASG MultiPurpose (CAMP) chamber. It is equipped with specially developed photon and charged particle detection devices dedicated to cover large solid-angles. A variety of different targets are supported, such as atomic, (aligned) molecular and cluster jets, particle injectors for bio-samples or fixed target arrangements. CAMP houses 4π solid-angle ion and electron momentum imaging spectrometers (“reaction microscope”, REMI, or “velocity map imaging”, VMI) in a unique combination with novel, large-area, broadband (50 eV–25 keV), high-dynamic-range, single-photon-counting and imaging X-ray detectors based on the pnCCDs. This instrumentation allows a new class of coherent diffraction experiments in which both electron and ion emission from the target may be simultaneously monitored. This permits the investigation of dynamic processes in this new regime of ultra-intense, high-energy radiation—matter interaction. After an introduction into the salient features of the CAMP chamber and the properties of the redesigned REMI/VMI spectrometers, the new 1024×1024 pixel format pnCCD imaging detector system will be described in detail. Results of tests of four smaller format (256×512) devices of identical performance, conducted at FLASH and BESSY, will be presented and the concept as well as the anticipated properties of the full, large-scale system will be elucidated. The data obtained at both radiation sources illustrate the unprecedented performance of the X-ray detectors, which have a voxel size of 75×75×450 μm3 and a typical read-out noise of 2.5 electrons (rms) at an operating temperature of −50 °C.

The German X-ray instrument eROSITA (extended ROentgen Survey with an Imaging Telescope Array) is the main instrument of the new Spectrum-RG mission orbiting at L2. The launch of the Russian satellite is planned for the year 2012. The scientific goal of eROSITA is primarily an all sky survey with detection and analysis of 100 thousand clusters of galaxies in order to study the large scale structures in the Universe and to test cosmological models. The therefore required large effective area is obtained by an array of seven identical and parallel aligned Wolter-I telescopes. The focal plane instrumentation is realized with a 384 × 384 pixel frame store pnCCD mounted on a ceramic PCB and cooled to -80 C. The ceramic PCB also houses three CAMEX readout ASICs to amplify and filter each of the 384 channels in parallel. The cooled ceramic is connected via a flex lead to the electronics box at room temperature. A copper housing shields for proton radiation whereas a graded-Z shield attenuates X-ray fluorescence.

Multi-Linear Silicon Drift Detectors (ML-SDDs) are a recent evolution of silicon drift detectors, in which the signal electrons generated by the interaction are confined within parallel drifting columns and transported towards point-like anodes by the electrostatic field. ML-SDDs can be operated both in integrate-readout and in free-running mode and are able to provide 2-D position sensing capability combined with spectroscopic energy-resolution. Therefore ML-SDDs open the way to time-resolved imaging and spectroscopy of X-rays and Compton electrons in addition to charged particle tracking. The excellent energy resolution and the relatively small Doppler broadening of silicon makes a ML-SDD detector an ideal candidate to reconstruct the original location of the gamma-ray with sub-millimeter position resolution. Novel designs of 1 cm2 and 3 cm2 ML-SDDs have been carried out and first detectors prototypes were produced at the Halbleiterlabor of the Max Planck Institut in cooperation with PNSensor GmbH. In this paper we will discuss the main detector performance in terms of position, energy and time resolution.

A detector that looks promising for advanced imaging modalities—such as X-ray absorption contrast imaging, X-ray fluorescence imaging, and diffraction-enhanced imaging—is the controlled-drift detector (CDD). The CDD is a novel two-dimensional X-ray imager with energy resolving capability of spectroscopic quality. It is built on a fully depleted silicon wafer and features fast readout while being operated at or near room temperature. The use of CDDs in the aforementioned applications allows translating these techniques from synchrotron-based experiments to laboratory-size experiments using polychromatic X-ray generators. We have built a dedicated and versatile detection module based on a 36 mm2 CDD chip featuring pixels of 180 × 180 μm2, and we evaluated the system performance in different X-ray imaging applications both with synchrotron-based experiments and in the laboratory environment.

Cryo-electron microscopy and especially cryo-electron tomography are widely applicable for structural studies in biology, but the major limitation is the extreme sensitivity of frozen hydrated biological samples to electron radiation [1–3]. Thus low-dose techniques have to be used, distributing the total electron dose (typically in the range of 50 electrons/Angstrom) to many single images, demanding highly sensitive recording devices. Phosphor-coated fiber coupled CCD cameras are typically used where the primary electrons are converted to visible light. This indirect detection strategy is characterized by significant levels of readout and dark current noise and the number of optical interfaces within the complete camera assembly results in multiple scattering and a subsequent loss in resolution. Since the total applied dose can’t be increased in cryo-EM studies, the improvement in camera performance with noiseless recording, a higher sensitivity and at the same time higher spatial resolution is therefore be definitely beneficial for low-dose cryo-applications [4,5].

A frame-store pn-junction CCD detector was applied to the energy-dispersive X-ray Laue diffraction study of a γ-LiAlO2crystal with white synchrotron radiation. Exploiting the simultaneous spatial and energy resolution of the detector the crystallographic unit cell of γ-LiAlO2could be determined without anya prioriinformation about the sample. The potential for application in X-ray structure analysis is tested by comparing experimental structure factors taken under a single exposure with those calculated from the known crystal structure. After correcting the measured spot intensities by angular and energy-dependent parameters, the agreement between experimental and theoretical kinematical structure factors is better than 10%.

The class of cellularly stratified algebras is defined and shown to include large classes of diagram algebras. While the definition is in combinatorial terms, by adding extra structure to Graham and Lehrer’s definition of cellular algebras, various structural properties are established in terms of exact functors and stratifications of derived categories. The stratifications relate ‘large’ algebras such as Brauer algebras to ‘smaller’ ones such as group algebras of symmetric groups. Among the applications are relative equivalences of categories extending those found by Hemmer and Nakano and by Hartmann and Paget, as well as identities between decomposition numbers and cohomology groups of ‘large’ and ‘small’ algebras.

Objective. Our aim was to determine the incidence of cervical and endometrial pathology associated with the diagnosis of histiocytes on cervical cytology. Materials and Methods. A retrospective review was conducted from 1993 to 1995 of cervical cytology reports in which histiocytes were named in the descriptive diagnosis. Charts were reviewed and follow-up was performed on all patients for an additional 2 years. Results. Histiocytes were diagnosed in 226 of 82,018 (0.27%) cytology reports. Histiocytes alone (110), histiocytes and endometrial cells (40), and histiocytes and inflammation (45) were reported in the patients with complete follow-up. Final pathological findings after 2 years of follow-up were normal in 169 cases; other findings included polyps (6), simple hyperplasia (10), complex hyperplasia (1), previously treated cervical cancer (4), and endometrial cancer (5). All patients with endometrial cancer had clinical signs and symptoms of disease. Conclusion. The diagnosis of histiocytes on cervical cytology is associated with neoplasia (7.8%) or cancer (2.6%) in some cases. However, significant neoplasia (i.e., carcinoma or atypical hyperplasia) was associated with clinical signs and symptoms. On cytological workup, the finding of histiocytes in the absence of symptoms appears not to be associated with significant pathology.

The Max-Planck-Institute semiconductor lab develops, fabricates, tests, and qualifies pnCCDs for space and ground based applications. pnCCDs are CCDs showing high quantum efficiency up to 20 keV while delivering good spatial and energy resolution. This article describes the algorithms applied to the raw data as recorded by the data acquisition system. The main purpose of the underlying software is to qualify the individual pnCCD by measurements of monoenergetic X-ray lines, from B-K (183 eV) to Mo-Kα (17.5 keV), typically Mn-Kα (5.9 keV) under various conditions (e.g. temperature, readout speed, electrical supply voltages of the detector and electronics). Therefore characteristic parameters are determined individually for each measurement as there are read noise, gains, charge transfer efficiencies, charge splitting between neighboring pixels, energy resolution, and bad pixels while correcting for offsets, gains, charge transfer inefficiencies, non-linearities of the electronics, and while recombining the charges spread over more than one pixel. These figures are used in three ways: Firstly, operating parameters are optimized by comparing individual measurements. Secondly, the individual device is rated by combining the results of all its measurements. Thus devices can be selected for applications such as measurement setups for DESY, FLASH, or the X-ray test facility PANTER. Especially the flight modules for the X-ray astronomy mission eROSITIA will be chosen based on the key figures. Thirdly, improvements gained from detector and electronics design and production modifications are quantified closing the development loop of pnCCDs and their associated electronics.

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 future photon sources (LCLS, SCSS and XFEL). 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 is developing and producing 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 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.

For the readout of pnCCD we developed a series of CAMEX ASICs since the early 90’s. With the advent of DEPFET PIXEL detectors the existing CAMEX readout chip was adopted for these new detectors. The actual generation of CAMEX readout chips is fabricated in a standard 5V CMOS technology with JFET option at the Fraunhofer IMS in Duisburg, Germany. To qualify the new CAMEX readout ASICs we performed several measurements including weighting function measurements, multiplexer performance and linearity as well as performance figures of the integrated bias DACs. Performance values together with the pnCCD will be shown. Further tests will also reveal the radiation performance of the ASIC. The main application of these CAMEX chips is the X-ray astronomy project eROSITA (extended Roentgen Survey with an Imaging Telescope Array). This X-ray telescope will be accommodated aboard the new Spectrum Roentgen Gamma satellite. It consists of seven parallel oriented mirror modules (Wolter-I optics) each having its own pnCCD camera in the focus. The pnCCD detector consists of 384×384 imaging pixels with 75μm size plus a frame store area. The satellite launch is planned for the year 2011.The parallel architecture of the pnCCD and CAMEX allows lownoise readout of a full 384 × 384 pixel image within ≪8 ms. Full size prototypes of the detector system are currently under test. Another application are detectors for the evolving X-ray free electron lasers, a new generation of synchrotron light sources. X-ray FEL facilities provide pulses of coherent X-ray light of high brilliance in the energy range of below 0.3 keV up to 24 keV. New prototype pnCCDs for these applications have a size of 512x1024 pixels and are readout with 8 CAMEX chips operating in parallel to archive a frame rate of up to 200Hz.

We present the design and optical imaging performance of a pnCCD detector system for highest frame rates and excellent sensitivity over a wide wavelength range from the UV to near IR region. To achieve frame rates higher than one thousand frames per second with an exceptionally low noise level, the devices are based on proven technology with column parallel readout and operated in a split–frame transfer mode. The CCDs are back illuminated and coated with an Anti–Reflective– Coating. The sensitivity over their full thickness of 450 μm allows for a quantum efficiency near 100 % over a wide spectral range. At an optical test bench we determined the photon transfer curve, quantum efficiency and point–spread function within a wavelength region between 300 nm to 1100 nm for various detector parameter. To demonstrate the ability of a pnCCD to perform high–speed optical differential photometry, the crab nebula with the crab pulsar as central object were observed at the 1.3 m SKINAKAS telescope on crete. For these observations the pnCCD was operated at a speed of 2000 frames per second. The high speed, low noise and high quantum efficiency makes this detector an ideal instrument to be used as a wavefront sensor in adaptive optics systems.

We report the latest development of a 1-kHz OPCPA system, generating carrier-envelope-phase-stabilized 350-µJ 20-fs pulses around 2.1 µm with suppressed superfluorescence. A proof-of-principle high-harmonic-generation experiment in argon was conducted, producing photons up to 250 eV.

We describe innovative topologies of Silicon Drift Detectors suitable for 2D position sensing applications with very fast readout (i.e. operating at high drift fields) and we report the experimental characterisation of two prototypes. The specific design issues taken into account in order to operate at high drift fields (e.g. able to achieve drift speeds of the order of 1 cm/μs) will be discussed. The designed detectors feature the possibility to independently bias the field-plates covering the inter-strip oxide in order to investigate the impact of the field-plate voltage on the transport properties and on the surface generated leakage current. In order to test the effectiveness of the proposed designs, a fast (100 ps) infrared pulsed laser, generating the desired signal charge, has been focused to a small spot (10 μm FWHM) on the front side of the detector and displaced along the drift and lateral directions to study the detector response. The experimental characterization, carried out close to room temperature, includes the assessment of the maximum drift field, of the achievable spatial resolution and of the lateral charge confinement.

We present the design, status of fabrication and testing, and expected performance characteristics of new CCDs for highest frame rates and excellent sensitivity over a wide wavelength range, from the near UV to the to near IR. To achieve frame rates in the kHz regime, the devices are based on proven technology with column parallel readout. The CCDs are back illuminated, sensitive over their full thickness of 450 μm, allowing a peak quantum efficiency near 100% at any chosen wavelength between 400 nm and 1,000 nm. Test results, including astronomical trials at Skinakas observatory, using available devices with an on‐chip JFET amplifier are presented. Based on the above CCD design we are currently producing two novel variants with single photon counting capabilities: They either use integrated avalanche diodes in the readout chain or a repetitive non‐destructive readout. Both readout schemes have already successfully proven their single‐photon sensitivity and we present the related results.

We define the cohomological Burnside ring B n (G, M) of a finite group G with coefficients in a Z G-module M as the Grothendieck ring of the isomorphism classes of pairs [X, u] where X is a G-set and u is a cohomology class in a cohomology group H X n (G, M). The cohomology groups H X * (G, M) are defined in such a way that H X * (G, M) ≅ ⊕ i H * (H i, M) when X is the disjoint union of transitive G-sets G / H i. If A is an abelian group with trivial action, then B 1 (G, A) is the same as the monomial Burnside ring over A, and when M is taken as a G-monoid, then B 0 (G, M) is equal to the crossed Burnside ring B c (G, M). We discuss the generalizations of the ghost ring and the mark homomorphism and prove the fundamental theorem for cohomological Burnside rings. We also give an interpretation of B 2 (G, M) in terms of twisted group rings when M = k × is the unit group of a commutative ring. © 2006 Elsevier Inc. All rights reserved.

© 2015 Author(s). Lensless x-ray microscopy requires the recovery of the phase of the radiation scattered from a specimen. Here, we demonstrate a de novo phase retrieval technique by encapsulating an object in a superfluid helium nanodroplet, which provides both a physical support and an approximate scattering phase for the iterative image reconstruction. The technique is robust, fast-converging, and yields the complex density of the immersed object. Images of xenon clusters embedded in superfluid helium droplets reveal transient configurations of quantum vortices in this fragile system.

A novel type of backside illuminated pnCCDs has been fabricated and successfully tested. The devices with a pixel size of 51 μm and an imaging area of 264×264 pixel, corresponding to a sensitive area of 13.5×13.5 mm, feature a framestore region for both sides of the detector. By splitting the image into two framestore areas during readout, repetition rates of more than 1000 frames per second were achieved. The electronic noise contribution of the entire detector system is slightly higher than two electrons at an operating concept of data acquisition system able to handle pixel rates of more than 70 megapixel per second. Decentral data reduction and analysis units allow for real-time data processing. For example, it allows determination of the centroid of a great number of sub-images in a Shack-Hartmann wavefront sensor with a very low latency time. Due to the large sensitive volume of the detector and the development of an ultra-thin backside contact, near theoretical quantum efficiencies are achieved from the ultraviolet to the nearinfrared. Detectors with optimized response in the visible and near-infrared regions were fabricated by implementing different types of anti-reflective coatings. The combination of very high speed, exceptionally low noise and high quantum efficiency makes these CCDs wavefront sensors in adaptive optics systems.

Single photon counting plays an essential role for a wide variety of applications, ranging from biomedical research to astronomy. In gamma-ray astronomy, the Cherenkov telescope MAGIC is used to detect Cherenkov photons generated in atmospheric air showers. Since the flux of Cherenkov photons from air showers is low, the development of new single photon detectors with high quantum efficiency is necessary. The concept of the Back Illuminated Drift Silicon Photomultiplier (BID SiPM) is a novel detector design for single photon counting. It combines the principles of a silicon photomultiplier (SiPM) and a drift diode. The back illuminated drift silicon photomultiplier is operated as back illuminated detector thus providing a fill factor of 100%. A high quantum efficiency of about 80% in a wavelength region of 300 - 1000 nm can be achieved. The drift region is used to focus electrons from the back through the depleted bulk to the small point-like avalanche region. The time jitter of the electrons limits the time resolution of the detector to about 1 ns as simulation results show. A prototype of an avalanche region which can be combined with a drift structure was produced at the MPI Semiconductor Laboratory as proof of principle. The detector concept and results of measurements of dark rate and leakage current are presented.

The relatively small doppler broadening of silicon and the excellent energy and position resolution of Controlled-Drift Detectors make these detectors suitable candidates as scatter detectors that allow reconstruction of the orginal location of the gamma-ray with ultimate position resolution. The achievable performance of such detectors allow imaging the 2D projection of the electron track and its ionization profile by sampling the charge desposted in each pixel. This feature would allow electron tracking not only for those electrons crossing more detection layers but also for low energy electrons, often totally absorbed in the interaction layer owing to the short electron range. The p0rojection of the initial direction of the recoil electron, the vertex of the interaction and the electron energy can therefore be more precisely estimate for wide range of Compton electron energies leading to improved resolution and efficiency. The paper presentw the results of the experimental characterization of a Controlled Drift Detector prototype in order to assess its capability in Compton electron tracking.

A new generation of pnCCDs has been developed for the proposed X-ray astronomy missions, DUO and ROSITA. The DUO/ROSITA CCD is a frame store pnCCD based on the concept of the XMM-Newton pnCCD and has both, improved performance and new features. This detector permits accurate spectroscopy of X-rays as well as imaging and high time resolution with high quantum efficiency in the energy band from 0.3 keV to 10 keV. Interfering electron-hole pair generation due to optical and UV light is prevented by a deposition of an on-chip filter. We describe the frame store pnCCDs developed and fabricated for the DUO and ROSITA missions in the semiconductor laboratory of the Max-Planck-Institut fuer extraterrestrische Physik. An overview about the CCD concept and design is given along with some details about the fabrication of the devices. In addition, we introduce a new analog signal processor which has been developed specifically for the readout of the frame store pnCCD signals. The main focus of this paper is to present the very first measurements with this CCD type and its analog signal processor. Towards this aim we report the operation of this new sensor and its key performance parameters. Finally we discuss ongoing and future tests with the DUO/ROSITA CCDs.

Extended abstract of a paper presented at Microscopy and Microanalysis 2013 in Indianapolis, Indiana, USA, August 4 – August 8, 2013.