A. Bergamaschi

Capturing dynamics with Eiger, a fast-framing X-ray detector

A high-frame-rate single-photon-counting pixel detector named Eiger and its suitability for X-ray photon correlation spectroscopy are described.

In situ observation of rapid reactions in nanoscale Ni–Al multilayer foils using synchrotron radiation

The observation of rapid reactions in nanoscale multilayers present challenges that require sophisticated analysis methods. We present high-resolution in situ x-ray diffraction analysis of reactions in nanoscale foils of Ni0.9V0.1–Al using the Mythen II solid-state microstrip detector system at the Material Science beamline of the Swiss Light Source Synchrotron at Paul Scherrer Institute in Villigen, Switzerland. The results reveal the temperature evolution corresponding to the rapid formation of NiAl intermetallic phase, vanadium segregation and formation of stresses during cooling, determined at high temporal (0.125 ms) and angular (0.004°) resolution over a full angular range of 120°.

The GOTTHARD charge integrating readout detector: design and characterization

A charge integrating readout ASIC (Application Specific Integrated Circuit) for silicon strip sensors has been developed at PSI in collaboration with DESY. The goal of the project is to provide a charge integrating readout system able to cope with the pulsed beam of XFEL machines and at the same time to retain the high dynamic range and single photon resolution performances typical for photon counting systems. The ASIC, designed in IBM 130 nm CMOS technology, takes advantage of its three gain stages with automatic stage selection to achieve a dynamic range of 10000 12 keV photons and a noise better than 300 e.n.c.. The 4 analog outputs of the ASIC are optimized for speed, allowing frame rates higher than 1 MHz, without compromises on linearity and noise performances. This work presents the design features of the ASIC, and reports the characterization results of the chip itself.

Prototype characterization of the JUNGFRAU pixel detector for SwissFEL

The SwissFEL, a free electron laser (FEL) based next generation X-ray source, is being built at PSI. An XFEL poses several challenges to the detector development: in particular the single photon counting readout, a successful scheme in case of synchrotron sources, can not be used. At the same time the data quality of photon counting systems, i.e. the low noise and the high dynamic range, is essential from an experimental point of view. Detectors with these features are under development for the EU-XFEL in Hamburg, with the PSI SLS Detector group being involved in one of these efforts (AGIPD). The pulse train time structure of the EU-XFEL machine forces the need of in pixel image storage, resulting in pixel pitches in the 200 μm range. Since the SwissFEL is a 100 Hz repetition rate machine, this constrain is relaxed. For this reason, PSI is developing a 75 μm pitch pixel detector that, thanks to its automatic gain switching technique, will achieve single photon resolution and a high dynamic range. The detector is modular, with each module consisting of a 4 × 8 cm2 active sensor bump bonded to 8 readout ASICs (Application Specific Integrated Circuit), connected to a single printed circuit readout board with 10GbE link capabilities for data download. We have designed and tested a 48 × 48 pixel prototype produced in UMC110 nm technology. In this paper we present the general detector and ASIC design as well as the results of the prototype characterization measurements.

Eiger: a single-photon counting x-ray detector

Eiger is a single-photon counting x-ray pixel detector being developed at the Paul Scherrer Institut (PSI) for applications at synchrotron light sources. It follows the widely utilized and successful Pilatus detector. The main features of Eiger are a pixel size of 75 × 75 μm2, high frame rate capability of 22 kHz and negligible dead time between frames of 4 μs. This article contains a detailed description of Eiger detector systems, from the 500 kpixel single-module detector to large-area multi-modules systems. The calibration and performance of the first 500 kpixel system that is in routine user operation are also presented. Furthermore, a method of calibrating the energy of single-photon counting detectors along the detector gain axis is introduced. This approach has the advantage that the detector settings can be optimized at all energies for count rate capabilities. Rate capabilities of the system are reported for energies between 6 and 16 keV.

EIGER a new single photon counting detector for X-ray applications: performance of the chip

EIGER is the next generation of single photon counting pixel detector for synchrotron radiation designed by the PSI-SLS detector group. It features a pixel size of 75 × 75μm2 and frame rates up to 23 kHz. The chip contains 256 × 256 pixels, has a total size of 19.3 × 20 mm2 and provides 4, 8 and 12 bit counting modes. This dynamic range is extendable to 32 bits with continuous read/write and summation of frames on the fly in firmware. Along with X-ray absorption images, the characterization and performance of the chip is presented. The energy calibration, noise, minimum energy threshold and rate capability measured with a single chip test system in a X-ray tube and at the SLS-PSI synchrotron are shown. Trimming studies and irradiation effects are discussed as well. To conclude, the status of the production of larger detector systems consisting of 2 × 4 chip modules and multi modules detector systems (9 Mpixels; 3 × 6 modules) is outlined.

MÖNCH, a small pitch, integrating hybrid pixel detector for X-ray applications

PSI is developing several new detector families based on charge integration and analog readout (CI) to respond to the needs of X-ray free electron lasers (XFELs), where a signal up to ~ 104 photons impinging simultaneously on a pixel make single photon counting detectors unusable. MONCH is a novel hybrid silicon pixel detector where CI is combined with a challengingly small pixel size of 25 × 25 μm2. CI enables the detector to process several incoming photon simultaneously in XFEL applications. Moreover, due to the small pixel size, the charge produced by an impinging photon is often shared. In low flux experiments the analog information provided by single photons can be used either to obtain spectral information or to improve the position resolution by interpolation. Possible applications are resonant and non-resonant inelastic X-ray scattering or X-ray tomography with X-ray tubes. Two prototype ASICs were designed in UMC 110 nm technology. MONCH01 contains only some test cells used to assess technology performance and make basic design choices. MONCH02 is a fully functional, small scale prototype of 4 × 4 mm2, containing an array of 160 × 160 pixels. This array is subdivided in five blocks, each featuring a different pixel architecture. Two blocks have statically selectable preamplifier gains and target synchrotron applications. In low gain mode they should provide single photon sensitivity (at 6-12 keV) as well as a reasonable dynamic range for such a small area ( > 120 photons). In high gain they target high resolution, low flux experiments where charge sharing can be exploited to reach μm resolution. Three other architectures address possible uses at XFELs and implement automatic switching between two gains to increase the dynamic range, as well as input overvoltage control. The paper presents the MONCH project and first results obtained with the MONCH02 prototype.

Single shot x-ray phase contrast imaging using a direct conversion microstrip detector with single photon sensitivity

X-ray phase contrast imaging enables the measurement of the electron density of a sample with high sensitivity compared to the conventional absorption contrast. This is advantageous for the study of dose-sensitive samples, in particular, for biological and medical investigations. Recent developments relaxed the requirement for the beam coherence, such that conventional X-ray sources can be used for phase contrast imaging and thus clinical applications become possible. One of the prominent phase contrast imaging methods, Talbot-Lau grating interferometry, is limited by the manufacturing, alignment, and photon absorption of the analyzer grating, which is placed in the beam path in front of the detector. We propose an alternative improved method based on direct conversion charge integrating detectors, which enables a grating interferometer to be operated without an analyzer grating. Algorithms are introduced, which resolve interference fringes with a periodicity of 4.7 μm recorded with a 25 μm pitch Si micro...

Micron resolution of MÖNCH and GOTTHARD, small pitch charge integrating detectors with single photon sensitivity

MONCH, a charge integrating readout ASIC (Application Specific Integrated Circuit) prototype with a pixel pitch of 25 μm developed at PSI, allows new imaging applications in the field of micron resolution and spectral imaging. The small pixel size of this system facilitates charge sharing between pixels, which then can be exploited to gain additional information about the photon absorption position and photon energy. However, for reconstructing complete images from this information, sufficient hits need to be recorded and therefore acquisition times are potentially long. We present a fast read-out system, that is capable of acquiring enough statistics for an image in a few hours in combination with a position reconstruction algorithm, which has the potential to run in a similar amount of time on a fast computing node. We further present results of experiments with a comparable strip detector (small-pitch GOTTHARD system) showing that with the aid of single photon interpolation algorithms micron resolution is achievable. Additionally, we show that a similar position reconstruction algorithm works in the two dimensional case for MONCH.

Towards hybrid pixel detectors for energy-dispersive or soft X-ray photon science

A novel hybrid pixel detector is evaluated and its potential for low-noise/low-energy detection and energy-dispersive photon science is highlighted.