Adaptive Gain Integrating Pixel Detector Research Articles

Expected resolution limits of x-ray free-electron laser single-particle imaging for realistic source and detector properties.

The unprecedented intensity of x-ray free-electron laser sources has enabled single-particle x-ray diffraction imaging (SPI) of various biological specimens in both two-dimensional projection and three dimensions (3D). The potential of studying protein dynamics in their native conditions, without crystallization or chemical staining, has encouraged researchers to aim for increasingly higher resolutions with this technique. The currently achievable resolution of SPI is limited to the sub-10 nanometer range, mainly due to background effects, such as instrumental noise and parasitic scattering from the carrier gas used for sample delivery. Recent theoretical studies have quantified the effects of x-ray pulse parameters, as well as the required number of diffraction patterns to achieve a certain resolution, in a 3D reconstruction, although the effects of detector noise and the random particle orientation in each diffraction snapshot were not taken into account. In this work, we show these shortcomings and address limitations on achievable image resolution imposed by the adaptive gain integrating pixel detector noise.

Analysis Strategies for MHz XPCS at the European XFEL

The nanometer length-scale holds precious information on several dynamical processes that develop from picoseconds to seconds. In the past decades, X-ray scattering techniques have been developed to probe the dynamics at such length-scales on either ultrafast (sub-nanosecond) or slow ((milli-)second) time scales. With the start of operation of the European XFEL, thanks to the MHz repetition rate of its X-ray pulses, even the intermediate μs range have become accessible. Measuring dynamics on such fast timescales requires the development of new technologies such as the Adaptive Gain Integrating Pixel Detector (AGIPD). μs-XPCS is a promising technique to answer many scientific questions regarding microscopic structural dynamics, especially for soft condensed matter systems. However, obtaining reliable results with complex detectors at free-electron laser facilities is challenging and requires more sophisticated analysis methods compared to experiments at storage rings. Here, we discuss challenges and possible solutions to perform XPCS experiments with the AGIPD at European XFEL; in particular, at the Materials Imaging and Dynamics (MID) instrument. We present our data analysis pipeline and benchmark the results obtained at the MID instrument with a well-known sample composed by silica nanoparticles dispersed in water.

Microsecond hydrodynamic interactions in dense colloidal dispersions probed at the European XFEL.

Many soft-matter systems are composed of macromolecules or nanoparticles suspended in water. The characteristic times at intrinsic length scales of a few nanometres fall therefore in the microsecond and sub-microsecond time regimes. With the development of free-electron lasers (FELs) and fourth-generation synchrotron light-sources, time-resolved experiments in such time and length ranges will become routinely accessible in the near future. In the present work we report our findings on prototypical soft-matter systems, composed of charge-stabilized silica nanoparticles dispersed in water, with radii between 12 and 15 nm and volume fractions between 0.005 and 0.2. The sample dynamics were probed by means of X-ray photon correlation spectroscopy, employing the megahertz pulse repetition rate of the European XFEL and the Adaptive Gain Integrating Pixel Detector. We show that it is possible to correctly identify the dynamical properties that determine the diffusion constant, both for stationary samples and for systems driven by XFEL pulses. Remarkably, despite the high photon density the only observable induced effect is the heating of the scattering volume, meaning that all other X-ray induced effects do not influence the structure and the dynamics on the probed timescales. This work also illustrates the potential to control such induced heating and it can be predicted with thermodynamic models.

Nanosecond X-ray photon correlation spectroscopy using pulse time structure of a storage-ring source

X-ray photon correlation spectroscopy (XPCS) is a routine technique to study slow dynamics in complex systems at storage-ring sources. Achieving nanosecond time resolution with the conventional XPCS technique is, however, still an experimentally challenging task requiring fast detectors and sufficient photon flux. Here, the result of a nanosecond XPCS study of fast colloidal dynamics is shown by employing an adaptive gain integrating pixel detector (AGIPD) operated at frame rates of the intrinsic pulse structure of the storage ring. Correlation functions from single-pulse speckle patterns with the shortest correlation time of 192 ns have been calculated. These studies provide an important step towards routine fast XPCS studies at storage rings.

Characterization of the AGIPD1.1 readout chip and improvements with respect to AGIPD1.0

Abstract AGIPD, the Adaptive Gain Integrating Pixel Detector, is a hybrid detector with a frame rate of 4.5 M H z , a dynamic range up to 1 0 4 ⋅ 12.4 k e V photons, as well as single photon resolution, developed for the European XFEL (Eu.XFEL). The final 1 Mpixel detector system consists of 16 tiled modules each one with 16 readout chips. The single ASIC is 64 x 64 pixels, each with a size of 200 x 200 μ m 2 . Each pixel can store up to 352 images. This work is focused on the characterization of AGIPD1.1, the second version of the full scale ASIC, and the improvements with respect to AGIPD1.0. From the measurements presented in this paper we show that the flaws observed in AGIPD1.0 (i.e. ghosting, crosstalk, slow readout speed) have been fixed in AGIPD1.1. In addition the main performance parameters such as noise, dynamic range and so on were measured for the new version of the ASIC and will be summarized.

Megapixels @ Megahertz – The AGIPD high-speed cameras for the European XFEL

The European XFEL is an extremely brilliant Free Electron Laser Source with a very demanding pulse structure: trains of 2700 X-ray pulses are repeated at 10 Hz. The pulses inside the train are spaced by 220 ns and each one contains up to 1012 photons of 12.4 keV, while being ≤100fs in length. AGIPD, the Adaptive Gain Integrating Pixel Detector, is a hybrid pixel detector developed by DESY, PSI, and the Universities of Bonn and Hamburg to cope with these properties. It is a fast, low noise integrating detector, with single photon sensitivity (for Eγ⪆6keV) and a large dynamic range, up to 104 photons at 12.4 keV. This is achieved with a charge sensitive amplifier with 3 adaptively selected gains per pixel. 352 images can be recorded at up to 6.5 MHz and stored in the in-pixel analogue memory and read out between pulse trains. The core component of this detector is the AGIPD ASIC, which consists of 64 × 64 pixels of 200µm×200µm. Control of the ASIC’s image acquisition and analogue readout is via a command based interface. FPGA based electronic boards, controlling ASIC operation, image digitisation and 10 GE data transmission interface AGIPD detectors to DAQ and control systems. An AGIPD 1 Mpixel detector has been installed at the SPB 1 experimental station in August 2017, while a second one is currently commissioned for the MID 2 endstation. A larger (4 Mpixel) AGIPD detector and one to employ Hi-Z sensor material to efficiently register photons up to Eγ≈25keV are currently under construction.

MHz data collection of a microcrystalline mixture of different jack bean proteins

We provide a detailed description of a serial femtosecond crystallography (SFX) dataset collected at the European X-ray free-electron laser facility (EuXFEL). The EuXFEL is the first high repetition rate XFEL delivering MHz X-ray pulse trains at 10 Hz. The short spacing (<1 µs) between pulses requires fast flowing microjets for sample injection and high frame rate detectors. A data set was recorded of a microcrystalline mixture of at least three different jack bean proteins (urease, concanavalin A, concanavalin B). A one megapixel Adaptive Gain Integrating Pixel Detector (AGIPD) was used which has not only a high frame rate but also a large dynamic range. This dataset is publicly available through the Coherent X-ray Imaging Data Bank (CXIDB) as a resource for algorithm development and for data analysis training for prospective XFEL users.

The Adaptive Gain Integrating Pixel Detector at theEuropean XFEL.

The Adaptive Gain Integrating Pixel Detector (AGIPD) is an X-ray imager, custom designed for the European X-ray Free-Electron Laser (XFEL). It is a fast, low-noise integrating detector, with an adaptive gain amplifier per pixel. This has an equivalent noise of less than 1 keV when detecting single photons and, when switched into another gain state, a dynamic range of more than 104 photons of 12 keV. In burst mode the system is able to store 352 images while running at up to 6.5 MHz, which is compatible with the 4.5 MHz frame rate at the European XFEL. The AGIPD system was installed and commissioned in August 2017, and successfully used for the first experiments at the Single Particles, Clusters and Biomolecules (SPB) experimental station at the European XFEL since September 2017. This paper describes the principal components and performance parameters of the system.

New calibration circuitry and concept for AGIPD

AGIPD (adaptive gain integrating pixel detector) is a detector system developed for the European XFEL (XFEL.EU), which is currently being constructed in Hamburg, Germany. The XFEL.EU will operate with bunch trains at a repetition rate of 10 Hz. Each train consists of 2700 bunches with a temporal separation of 220 ns corresponding to a rate of 4.5 MHz. Each photon pulse has a duration of < 100 fs (rms) and contains up to 1012 photons in an energy range between 0.25 and 25 keV . In order to cope with the large dynamic range, the first stage of each bump-bonded AGIPD ASIC is a charge sensitive preamplifier with three different gain settings that are dynamically switched during the charge integration. Dynamic gain switching allows single photon resolution in the high gain stage and can cover a dynamic range of 104 × 12.4 keV photons in the low gain stage. The burst structure of the bunch trains forces to have an intermediate in-pixel storage of the signals. The full scale chip has 352 in-pixel storage cells inside the pixel area of 200 × 200 μm2. This contribution will report on the measurements done with the new calibration circuitry of the AGIPD1.1 chip (without sensor). These results will be compared with the old version of the chip (AGIPD1.0). A new calibration method (that is not AGIPD specific) will also be shown.

Characterization of AGIPD1.0: The full scale chip

The AGIPD (adaptive gain integrating pixel detector) detector is a high frame rate (4.5MHz) and high dynamic range (up to 104 ·12.4keV photons) detector with single photon resolution (down to 4keV taking 5σ as limit and lowest noise settings) developed for the European XFEL (XFEL.EU). This work is focused on the characterization of AGIPD1.0, which is the first full scale version of the chip. The chip is 64×64 pixels and each pixel has a size of 200×200μm2. Each pixel can store up to 352 images at a rate of 4.5MHz (corresponding to 220ns). A detailed characterization of the AGIPD1.0 chip has been performed in order to assess the main performance of the ASIC in terms of gain, noise, speed and dynamic range. From the measurements presented in this paper a good uniformity of the gain, a noise around 320 e− (rms) in standard mode and around 240 e− (rms) in high gain mode has been measured. Furthermore a detailed discussion about the non-linear behavior after the gain switching is presented with both experimental results and simulations.

The adaptive gain integrating pixel detector

The adaptive gain integrating pixel detector (AGIPD) is a development of a collaboration between Deustsches Elektronen-Synchrotron (DESY), the Paul-Scherrer-Institute (PSI), the University of Hamburg and the University of Bonn. The detector is designed to cope with the demanding challenges of the European XFEL. Therefore it comes along with an adaptive gain stage allowing a high dynamic range, spanning from single photon sensitivity to 104 × 12.4 keV photons and 352 analogue memory cells per pixel. The aim of this report is to briefly explain the concepts of the AGIPD electronics and mechanics and then present recent experiments demonstrating the functionality of its key features.

Front end ASIC for AGIPD, a high dynamic range fast detector for the European XFEL

The Adaptive Gain Integrating Pixel Detector (AGIPD) is a hybrid pixel X-ray detector for the European-XFEL. One of the detector's important parts is the radiation tolerant front end ASIC fulfilling the European-XFEL requirements: high dynamic range—from sensitivity to single 12.5keV-photons up to 104 photons. It is implemented using the dynamic gain switching technique with three possible gains of the charge sensitive preamplifier. Each pixel can store up to 352 images in memory operated in random-access mode at ⩾4.5 MHz frame rate. An external vetoing may be applied to overwrite unwanted frames.

X-CSIT: a toolkit for simulating 2D pixel detectors

A new, modular toolkit for creating simulations of 2D X-ray pixel detectors, X-CSIT (X-ray Camera SImulation Toolkit), is being developed. The toolkit uses three sequential simulations of detector processes which model photon interactions, electron charge cloud spreading with a high charge density plasma model and common electronic components used in detector readout. In addition, because of the wide variety in pixel detector design, X-CSIT has been designed as a modular platform so that existing functions can be modified or additional functionality added if the specific design of a detector demands it. X-CSIT will be used to create simulations of the detectors at the European XFEL, including three bespoke 2D detectors: the Adaptive Gain Integrating Pixel Detector (AGIPD), Large Pixel Detector (LPD) and DePFET Sensor with Signal Compression (DSSC). These simulations will be used by the detector group at the European XFEL for detector characterisation and calibration. For this purpose, X-CSIT has been integrated into the European XFEL's software framework, Karabo. This will further make it available to users to aid with the planning of experiments and analysis of data. In addition, X-CSIT will be released as a standalone, open source version for other users, collaborations and groups intending to create simulations of their own detectors.

AGIPD, a high dynamic range fast detector for the European XFEL

AGIPD—(Adaptive Gain Integrating Pixel Detector) is a hybrid pixel X-ray detector developed by a collaboration between Deutsches Elektronen-Synchrotron (DESY), Paul-Scherrer-Institut (PSI), University of Hamburg and the University of Bonn. The detector is designed to comply with the requirements of the European XFEL. The radiation tolerant Application Specific Integrated Circuit (ASIC) is designed with the following highlights: high dynamic range, spanning from single photon sensitivity up to 104 12.5keV photons, achieved by the use of the dynamic gain switching technique using 3 possible gains of the charge sensitive preamplifier. In order to store the image data, the ASIC incorporates 352 analog memory cells per pixel, allowing also to store 3 voltage levels corresponding to the selected gain. It is operated in random-access mode at 4.5MHz frame rate. The data acquisition is done during the 99.4ms between the bunch trains. The AGIPD has a pixel area of 200× 200 μ m2 and a 500μ m thick silicon sensor is used. The architecture principles were proven in different experiments and the ASIC characterization was done with a series of development prototypes. The mechanical concept was developed in the close contact with the XFEL beamline scientists and is now being manufactured. A first single module system was successfully tested at APS.

Intensity interferometry of single x-ray pulses from a synchrotron storage ring.

We report on measurements of second-order intensity correlations at the high-brilliance storage ring PETRA III using a prototype of the newly developed adaptive gain integrating pixel detector. The detector records individual synchrotron radiation pulses with an x-ray photon energy of 14.4keV and repetition rate of about 5MHz. The second-order intensity correlation function is measured simultaneously at different spatial separations, which allows us to determine the transverse coherence length at these x-ray energies. The measured values are in a good agreement with theoretical simulations based on the Gaussian Schell model.

AGIPD detector for Serial Femtosecond Crystallography Apparatus at European XFEL

The European X-ray Free-Electron Laser (XFEL.EU) [1] will provide ultra-short, highly-intense, coherent x-ray pulses at an unprecedented repetition rate, transforming experiments in many scientific areas, including serial femtosecond crystallography (SFX). For the purpose of SFX experiments at the XFEL.EU, a dedicated endstation is being developed to be installed within the Single Particles, Clusters and Biomolecules (SPB) instrument [2]. The setup will refocus the beam spent by SPB into a second interaction region, thereby enabling two parallel experiments. In order to overcome various challenges in XFEL crystallography, and to optimize the output for SFX experiments at XFEL.EU, the Adaptive Gain Integrating Pixel Detector (AGIPD) [3] is currently under development and is to be implemented in the SPB instrument, including a 4 Megapixel version for the SFX apparatus. The AGIPD is a hybrid-pixel detector with pixels of 200 x 200 micron^2 each. The gain of each single pixel dynamically and independently adapts to the incoming signal. Thus, diffraction patterns of high dynamic range can be recorded, with the measured signal within a single data frame ranging from single photons and up to 1e+4 photons at 12 keV. Moreover, the AGIPD is designed to store over 350 data frames from successive pulses prior to digitization and read-out, thereby enabling operation at the European XFEL with its challenging repetition rate with 10 Hz pulse trains and a 4.5 MHz intra-train repetition rate. Furthermore, the incorporation of a veto system in AGIPD will allow one to potentially store only the frames that contain diffraction data from actual crystal hits, which ultimately increases the efficiency of the detector and DAQ systems dramatically. In the present work, we will review the design of the 4Mpix AGIPD for the SFX apparatus and discuss simulations and tests of its expected performance under the conditions foreseen for SFX experiments at the XFEL.EU.

Serial Femtosecond Crystallography user's consortium apparatus at European XFEL

The Serial Femtosecond Crystallography (SFX) user's consortium apparatus is to be installed within the Single Particles, Clusters and Biomolecules (SPB) instrument of the European X-ray Free-Electron Laser facility (XFEL.EU) [1, 2]. The XFEL.EU will provide ultra-short, highly intense, coherent X-ray pulses at an unprecedented repetition rate. The experimental setup and methodological approaches of many scientific areas will be transformed, including structural biology that could potentially overcome common problems and bottlenecks encountered in crystallography, such as creating large crystals, dealing with radiation damage, or understanding sub-picosecond time-resolved phenomena. The key concept of the SFX method is based on the kinetic insertion of protein crystal samples in solution via a gas dynamic virtual nozzle jet and recording diffraction signals of individual, randomly oriented crystals passing through the XFEL beam, as first demonstrated by Chapman et al. [3]. The SFX-apparatus will refocus the beam spent by the SPB instrument into a second interaction region, in some cases enabling two parallel experiments. The planned photon energy range at the SPB instrument is from 3 to 16 keV. The Adaptive Gain Integrating Pixel Detector (AGIPD) is to be implemented in the SPB instrument, including a 4 Megapixel version for the SFX-apparatus. The AGIPD is designed to store over 350 data frames from successive pulses, and aims to collect more than 3,000 images per second. Together with the implementation of automated procedures for sample exchange and injection, high-throughput nanocrystallography experiments can be integrated at the SFX-apparatus. In this work, we review the overall design of the SFX-apparatus and discuss the main parameters and challenges

Study of X-ray radiation damage in the AGIPD sensor for the European XFEL

The European X-ray Free Electron Laser (XFEL), currently being constructed in Hamburg and planned to be operational in 2017 for users, will deliver 27,000 fully coherent, high brilliance X-ray pulses per second with duration less than 100 fs. The unique features of the X-ray beam pose major challenges for silicon detectors used at the European XFEL for imaging experiments, in particular a radiation tolerance of silicon sensors for doses up to 1 GGy for 3 years of operation at an operating voltage above 500 V.One of the detectors under development at the European XFEL is the Adaptive Gain Integrating Pixel Detector (AGIPD), which is a hybrid detector system with ASICs bump-bonded to p+n silicon pixel sensors. We have designed the silicon sensors for the AGIPD, which have been fabricated by SINTEF and delivered in the beginning of February 2013. To demonstrate the performance of the AGIPD sensor with regard to radiation hardness, mini-sensors with the same pixel and guard-ring designs as the AGIPD together with test structures have been irradiated at the beamline P11 of PETRA III with 8 keV and 12 keV monoenergetic X-rays to dose values up to 10 MGy. The radiation hardness of the AGIPD sensor has been proven and all electrical properties are within specification before and after irradiation. In addition, the oxide-charge density and surface-current density from test structures have been characterized as function of the X-ray dose and compared to previous measurements for test structures produced by four vendors.

Optimization of the noise performance of the AGIPD prototype chips

The charge integrating readout electronics AGIPD(adaptive gain integrating pixel detector) is a hybrid detector system developed for theEuropean XFEL. It features a threefold dynamic gain switching to be able toresolve single photons and to cover a dynamic range of 104·12.4 keV photons. As a result of dynamic gain switching, single photonresolution will be achieved in the high gain stage, while the maximumdynamic range will be reached in the low gain stage.The specification to resolve single photons requires a signal-over-noiseratio of at least 10 for a single incoming photon with an energy of 12.4 keV. When using a silicon sensor, that translates to an equivalent noisecharge of less than 343 e−. Several AGIPD prototype chips have beendesigned and characterized, particularly focusing on the noise performance.During the testing phase, the dominant noise sources were identified and thecorresponding circuit blocks were improved in the subsequent ASICs.This paper reports on the procedures to identify the dominating noisesources, the optimization process of the circuit blocks and discusses theeffect of the optimization on the noise performance.

Performance tests of an AGIPD 0.4 assembly at the beamline P10 of PETRA III

The Adaptive Gain Integrating Pixel Detector (AGIPD) is a novel detector system, currently under development by a collaboration of DESY, the Paul Scherrer Institute in Switzerland, the University of Hamburg and the University of Bonn, and is primarily designed for use at the European XFEL. To verify key features of this detector, an AGIPD 0.4 test chip assembly was tested at the P10 beamline of the PETRA III synchrotron at DESY. The test chip successfully imaged both the direct synchrotron beam and single 7.05 keV photons at the same time, demonstrating the large dynamic range required for XFEL experiments. X-ray scattering measurements from a test sample agree with standard measurements and show the chip's capability of observing dynamics at the microsecond time scale.