Yang X., Jejkal T., Pasic H., Stotzka R., Streit A., Van Wezel J., Rolo T.D.S.

in Proceedings of the 2013 21st Euromicro International Conference on Parallel, Distributed, and Network-Based Processing, PDP 2013 (2013) 86-93, 6498537. DOI:10.1109/PDP.2013.21


In this paper, the method of data intensive computing is studied for large amounts of data in computed tomography (CT). An automatic workflow is built up to connect the tomography beamline of ANKA with the large scale data facility (LSDF), able to enhance the data storage and analysis efficiency. In this workflow, this paper focuses on the parallel computing of 3D computed tomography reconstruction. Different from the existing reconstruction system with filtered back-projection method, an algebraic reconstruction technique based on compressive sampling theory is presented to reconstruct the data from ultrafast computed tomography with fewer projections. Then the connected computing resources at the LSDF are used to implement the 3D CT reconstruction by distributing the whole job into multiple tasks executed in parallel. Promising reconstruction images and high computing performance are reported. For the 3D X-ray CT reconstruction, less than six minutes are actually required. LSDF is not only able to organize data efficiently, but also can provide reconstructed results to users in nearly instantaneous time. After integration into the workflow, this data intensive computing method will largely improve the data processing for ultrafast computed tomography at ANKA. © 2013 IEEE.

Mangold S., Steininger R., Rolo T.D.S., Gottlicher J.

in Journal of Physics: Conference Series, 430 (2013), 012130. DOI:10.1088/1742-6596/430/1/012130


Full field transmission spectroscopic imaging is a powerful method for screening complex and large systems to map the distribution of valence state and electronic configuration of elements. Here, we describe an optimized hardware set-up and data evaluation tool chain for spectroscopic X-ray imaging. We tested this system successful on a ferruginous quartz (SiO2) sample.

Giubilato P., Battaglia M., Bisello D., Caselle M., Chalmet P., Demaria L., Ikemoto Y., Kloukinas K., Mansuy S.C., Mattiazzo S., Marchioro A., Mugnier H., Pantano D., Potenza A., Rivetti A., Rousset J., Silvestrin L., Snoeys W.

in Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 731 (2013) 146-153. DOI:10.1016/j.nima.2013.04.042


The LePix projects aim realizing a new generation monolithic pixel detectors with improved performances at lesser cost with respect to both current state of the art monolithic and hybrid pixel sensors. The detector is built in a 90 nm CMOS process on a substrate of moderate resistivity. This allows charge collection by drift while maintaining the other advantages usually offered by MAPS, like having a single piece detector and using a standard CMOS production line. The collection by drift mechanism, coupled to the low capacitance design of the collecting node made possible by the monolithic approach, provides an excellent signal to noise ratio straight at the pixel cell together with a radiation tolerance far superior to conventional un-depleted MAPS. The excellent signal-to-noise performance is demonstrated by the device ability to separate the 6 keV 55Fe double peak at room temperature. To achieve high granularity (10-20 μm pitch pixels) over large detector areas maintaining high readout speed, a completely new compressing architecture has been devised. This architecture departs from the mainstream hybrid pixel sparsification approach, which uses in-pixel logic to reduce data, by using topological compression to minimize pixel area and power consumption. © 2013 Elsevier B.V.

Caselle M., Chilingaryan S., Herth A., Kopmann A., Stevanovic U., Vogelgesang M., Balzer M., Weber M.

in IEEE Transactions on Nuclear Science, 60 (2013) 3669-3677, 6510495. DOI:10.1109/TNS.2013.2252528


X-ray computer tomography is a powerful method for nondestructive investigations in many fields. Three-dimensional images of internal structure are reconstructed from a sequence of two-dimensional projections. The polychromatic high density photon flux of modern synchrotron light sources offer hard X-ray imaging with spatio-temporal resolution up to the micrometer and micrometers range. Existing indirect X-ray image detection systems can be adapted for fast image acquisition by high-speed visible-light cameras. In this paper, we present a platform for custom high-speed CMOS cameras with embedded field-programmable gate array (FPGA) processing. This modular system is characterized by a high-throughput PCI Express (PCIe) interface and efficient communication blocks. It has been used to develop a novel architecture for a self-event trigger that increases the effective image frame rate and reduces the amount of received data. Thanks to a low-noise design, high frame rates in the kilohertz range, and high-throughput data transfer, this camera is well suited for ultrafast synchrotron-based X-ray radiography and tomography. The camera setup is accomplished by high-throughput Linux drivers and a seamless integration in our GPU computing framework. © 2013 British Crown Copyright.

Zabler S., Ershov A., Rack A., Garcia-Moreno F., Baumbach T., Banhart J.

in Acta Materialia, 61 (2013) 1244-1253. DOI:10.1016/j.actamat.2012.10.047


Semi-solid melts exhibit a very unpredictable rheology and filling dynamics, when injected into thin-walled components. Optimization of the process requires an insight into the casting process during injection. For this purpose we injected semi-solid an Al-Ge alloy into two different thin channel geometries while recording high resolution radiographs at fast frame rates (up to 1000 images per s). Comparison of a bottleneck channel, which has previously been used for slower experiments, with a right-angle turn geometry reveals a significant influence of the channel shape on the flow behaviour of the particle-liquid mixture. While the bottleneck is quickly sealed with densified solid, turbulences in the right-angle turn apparently permit solid particles and clusters to move conjointly with the liquid and thus achieve a more complete filling. Single particle trajectories and rapid break-up of solid skeletons in such a system have been observed for the first time in situ. © 2012 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Moosmann J., Altapova V., Helfen L., Hanschke D., Hofmann R., Baumbach T.

in Journal of Physics: Conference Series, 425 (2013), 192003. DOI:10.1088/1742-6596/425/19/192003


Considering a pure and not necessarily weak phase object, we review a noniterative and nonlinear single-distance phase-retrieval algorithm. The latter exploits the fact that a well-known linear contrast-transfer function, which incorporates all orders in object-detector distance, can be modified to yield a quasiparticle dispersion. Accepting a small loss of information, this algorithm also retrieves the high-frequency parts of the phase in an artefact free way. We point out an extension of this highly resolving quasiparticle approach for mixed objects by assuming a global attenuation-phase duality. Tomographically reconstructing two developmental stages in Xenopus laevis, we compare our approach with a linear algorithm, based on the transport-of-intensity equation, which suppresses high-frequency information.

Myagotin A., Voropaev A., Helfen L., Hanschke D., Baumbach T.

in IEEE Transactions on Image Processing, 22 (2013) 5348-5361, 6631501. DOI:10.1109/TIP.2013.2285600


Computed laminography (CL) was developed to use X-rays from synchrotron sources for high-resolution imaging of the internal structure of a flat specimen from a series of 2-D projection images. The projections are acquired by irradiation of the sample under different rotation angles where the object rotation axis is inclined with respect to the beam direction. This yields for laterally extended objects a more uniform average transmitted intensity during sample rotation compared with computed tomography (CT). The reconstruction problem of CL cannot be reduced to a data-efficient 2-D case (as for parallelbeam CT) since each single slice perpendicular to the rotation axis requires a 2-D region on the detector as input data for all projection directions. This paper describes a computationally efficient reconstruction procedure based on filtered backprojection (FBP) adapted to the CL acquisition geometry. From the Fourier slice theorem, we derive a framework for analytic image reconstruction and outline implementation details of the generic FBP algorithm. Different approaches reducing the reconstruction time by means of parallel and distributed computations are considered and evaluated. © 2013 IEEE.

Potenza A., Bisello D., Caselle M., Costa M., Demaria N., Giubilato P., Ikemoto Y., Mansuy C., Marchioro A., Mattiazzo S., Moll M., Pacher L., Pacifico N., Pantano D., Rivetti A., Silvestrin L., Snoeys W.

in Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 718 (2013) 347-349. DOI:10.1016/j.nima.2012.10.020


The LePix project aims at developing monolithic pixel detectors in a 90 nm CMOS technology ported on moderate resistivity substrate. The radiation tolerance of the base material, which is an order of magnitude higher doped than standard high resistivity detectors, and which underwent the full advanced CMOS process, has been investigated. Diodes of about 1 mm2 and pixel matrices were irradiated with neutrons at fluences from 1012 n/cm2 to 2 × 1015 n/cm2 and characterized using CV and IV measurements. Matrices have also been irradiated with Xrays and withstand at least 10 Mrad. © 2012 Elsevier B.V. All rights reserved.

Mattiazzo S., Battaglia M., Bisello D., Caselle M., Chalmet P., Demaria N., Giubilato P., Ikemoto Y., Kloukinas K., Mansuy C., Marchioro A., Mugnier H., Pantano D., Potenza A., Rivetti A., Rousset J., Silvestrin L., Snoeys W., Wyss J.

in Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 718 (2013) 288-291. DOI:10.1016/j.nima.2012.10.098


We present a monolithic pixel sensor developed in the framework of the LePIX project aimed at tracking/triggering tasks where high granularity, low power consumption, material budget, radiation hardness and production costs are a concern. The detector is built in a 90 nm CMOS process on a substrate of moderate resistivity. This maintains the advantages usually offered by Monolithic Active Pixel Sensors (MAPS), like a low input capacitance, having a single piece detector and using a standard CMOS production line, but offers charge collection by drift from a depleted region and therefore an excellent signal to noise ratio and a radiation tolerance superior to conventional undepleted MAPS. Measurement results obtained with the first prototypes from laser, radioactive source and beam test experiments are described. The excellent signal-to-noise performance is demonstrated by the capability of the device to separate the peaks in the spectrum of a 55Fe source. We will also highlight the interaction between pixel cell design and architecture which points toward a very precise direction in the development of such depleted monolithic pixel devices for high energy physics. © 2012 Elsevier B.V. All rights reserved.

Alaribe L., Fauler A., Cecilia A., Santos Rolo T.D., Fiederle M., Burger A.

in International Journal of Microwave and Wireless Technologies, 1576 (2013). DOI:10.1557/opl.2013.1143


© Materials Research Society 2013. Much has been reported on the excellent performance of the Eu2+ activated SrI2-scintillator in spectroscopic applications, like the high light yield (97 660 ph/MeV) and good energy resolution (2.7% FWHM at 662 keV). The exploitation of these properties for other application fields is limited by the hygroscopic nature of the SrI2. Single crystal scintillating screens exhibit high spatial resolution, this combined with the high density, high effective atomic number, and the high light yield of the SrI2 could be used for high resolution X-ray imaging. Some of the questions we tried to answer in this work are the following: owing to the excellent performance of the SrI2-scintillator in spectroscopic applications, how would it perform in X-ray imaging applications. X-ray images are described based on their (spatial) resolution and contrast, how would they look like when recorded using the SrI2-scintillator detector. First a packaging technique was developed that protected the hygroscopic screens during the measurements. Our results show a high resolution of the images obtained with thin SrI2-scintillator screens both in 2D radiography and 3D tomography measurements. With these results, we think that the SrI2-scinitillator is not only a candidate for spectroscopic applications, but also for high resolution X-ray imaging purposes.