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[en] The FRONTier RADiography (FRONTRAD) collaboration is developing a digital system for mammography at the Elettra Synchrotron Light Source in Trieste. The system is based on a silicon microstrip detector array. The ASIC FROST (FRONTRAD Read Out sySTem) was developed as a collaboration between INFN Trieste and Aurelia Microelettronica and is designed to operate in single photon counting mode. FROST provides low-noise and high-gain performances and is able to work at incident photon rates higher than 100 kHz with almost 100% efficiency. The ASIC has been tested and the first images of mammographic test objects will be shown. The acquisition time per breast image should be of about 10 s
[en] The SYRMEP beam line is currently in the upgrading phase for mammographic examinations on patients at Elettra in Trieste. At the same time, a digital detection system, suitable for in -vivo breast imaging, is under development; it consists of a silicon laminar detector array operating in single photon counting mode. The duration of a clinical examination should not exceed a few seconds. Fast read out electronics is therefore necessary with the aim of avoiding losses in image contrast in presence of high counting rates. A custom ASIC working with 100% efficiency for rates up to 100 kHz per pixel has been designed and tested, and other solutions based on commercially available ASICs are currently under test. Several detector prototypes have been assembled, and images of mammographic test objects have been acquired. Image quality, efficiency and contrast losses have been evaluated in all cases as a function of the counting rate
[en] The SYRMEP/FRONTRAD experiment, active at the synchrotron radiation facility ELETTRA in Trieste, is developing a system for digital mammography with synchrotron radiation. Images of test-objects and of in vitro breast tissue samples have been acquired with both a custom developed linear array Si pixel detector and conventional film-screen systems. The beamline is currently being upgraded for in vivo experimentation. The X-ray beams used for the SYRMEP experiment are monochromatic and laminar, and images are acquired by scanning the sample through the beam. Thus, it is not possible to use the instrumentation and dosimetric protocols used in conventional mammography, in which polychromatic cone beams are used. In this paper, we describe the protocols under development for in vivo breast imaging
[en] The wiggler X-ray source of the Materials Science beamline at the Swiss Light Source has been replaced with a 14 mm-period cryogenically cooled in-vacuum undulator. In order to best exploit the increased brilliance of this new source, the entire front-end and optics have been redesigned. The Materials Science beamline at the Swiss Light Source has been operational since 2001. In late 2010, the original wiggler source was replaced with a novel insertion device, which allows unprecedented access to high photon energies from an undulator installed in a medium-energy storage ring. In order to best exploit the increased brilliance of this new source, the entire front-end and optics had to be redesigned. In this work, the upgrade of the beamline is described in detail. The tone is didactic, from which it is hoped the reader can adapt the concepts and ideas to his or her needs
[en] Synchrotron radiation applications require detectors with a high sensitivity and a large dynamic range in order to study both the strong and weak features of the samples. Moreover, a high spatial resolution is necessary for imaging and diffraction studies. The photon counting technique is currently the best solution to these requirements but it presents some limitations which can only be partially overcome by technological improvements i.e. the count loss at high impinging intensities, due to the readout electronics shaping time, and the restrictions on the minimum pixel size, due to the charge diffusion in the sensor. In order to overcome both these limitations a new generation of charge integrating hybrid detectors with single photon sensitivity is being developed. These preserve the advantages of counting detectors and at the same time allow a processing of the analog information in order to enhance the spatial resolution and perform some spectral analysis. A comparison between purely counting and analog readout for 50 and 25μm pitch microstrip detectors is presented in terms of spectral reconstruction capability and spatial resolution.
[en] 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.
[en] MÖNCH is a 25 μm pitch hybrid silicon pixel detector with a charge integrating analog read-out front-end in each pixel. The small pixel size brings new challenges in bump-bonding, power consumption and chip design. The MÖNCH02 prototype ASIC, manufactured in UMC 110 nm technology with a field of view of 4×4 mm"2 and 160×160 pixels, has been characterized in the single photon regime, i.e. with less than one photon acquired per frame on average on a 3×3 pixel cluster. The low noise and small pixel size allow spatial interpolation with high resolution. Understanding charge sharing as a function of the photon absorption depth and sensor bias is a key for optimal processing of single photon data for high resolution imaging. To characterize the charge collection of the detector, the sensor was illuminated with a 20 keV photon beam in edge-on configuration at the SYRMEP beamline of Elettra. By slicing the beam by means of a 5 μm slit and scanning through the 320 μm silicon sensor depth, the charge collection is characterized as a function of the photon absorption depth for different sensor bias voltages
[en] EIGER is a single photon counting hybrid pixel detector being developed at Paul Scherrer Institute (PSI), Switzerland, for applications at synchrotron light sources in an energy range from a few to 25 keV. EIGER is characterized by a small pixel size (75 × 75 μm"2), a frame rate up to 22 kHz and a small dead time between frames (4 μs). An EIGER module is a hybrid detector composed of a ≈ 8 × 4 cm"2 monolithic silicon sensor bump bonded to 4 × 2 readout chips, for a total of 500 kpixels. Each pixel has a configurable depth (up to 12 bits) counter and records the number of photons impinging. Custom designed module electronics reads out the bits in the pixel counter and processes the data in the module before transferring them to a PC. A large dynamic range (32 bits) for the pixel counter can be obtained through on-board image summation. Rate corrections can be applied on-board to compensate for inefficiencies when the pixel counting rates approach pile-up levels around a million counts per second. The EIGER modules are the building blocks of large area detectors: a 1.5 and a 9 Mpixel systems are under development for the cSAXS beamline at the Swiss Light Source (SLS) at PSI. The very high frame rate capabilities are equally fast for multi-module systems due to the fully parallel data processing.The module calibration will be discussed, with emphasis on the choice of the optimal operation settings as a function of photon energy. The performance regarding threshold dispersion and minimum achievable threshold will be presented. In addition, the progress towards the production of larger multi-module systems will be discussed
[en] The SLS detector group develops silicon hybrid detectors for X-ray applications used in synchrotron facilities all over the world. Both microstrip and pixel detectors with either single photon counting or charge integrating read out are being developed. Low noise charge integrating detectors can be operated in single photon regime, i.e. with low fluxes and high frame rates in order to detect on average less than one photon per cluster of 2×2 pixels. In this case, the analog signal read out for each single X-ray provides information about the energy of the photon. Moreover the signal from neighboring channels can be correlated in order to overcome or even take advantage of charge sharing. The linear charge collection model describing microstrip detectors and large pixels is unsuitable for the calibration of small pitch pixel detectors due to the large amount of charge sharing occurring also in the corner region. For this reason, the linear charge collection model is extended to the case of small pixels and tested with monochromatic X-ray data acquired using the 25 μm pitch MÖNCH and the 75 μm pitch JUNGFRAU detectors. The successful outcome of the calibration of the MÖNCH detector is proven by the high energy resolution of the spectrum obtained by accumulating the counts from more than 6000 channels after the correction of the gain mismatches using the proposed model
[en] The MYTHEN detector is a one-dimensional microstrip detector with single photon counting readout optimized for time resolved powder diffraction experiments at the Swiss Light Source (SLS). The system has been successfully tested for many different synchrotron radiation applications including phase contrast and tomographic imaging, small angle scattering, diffraction and time resolved pump and probe experiments for X-ray energies down to 5 keV and counting rate up to 3 MHz. The frontend electronics is designed in order to be coupled to 50 μm pitch microstrip sensors but some interest in enhancing the spatial resolution is arising for imaging and powder diffraction experiments. A test structure with strip pitches in the range 10-50 μm has been tested and the gain and noise on the readout electronics have been measured for the different strip pitches, observing no large difference down to 25 μm. Moreover, the effect of the charge sharing between neighboring strips on the spatial resolution has been quantified by measuring the Point Spread Function (PSF) of the system for the different pitches