Gasilov S., Dos Santos Rolo T., Mittone A., Polyakov S., Terentyev S., Farago T., Blank V., Bravin A., Baumbach T.

in Optics Express, 25 (2017) 25090-25097. DOI:10.1364/OE.25.025090

Abstract

© 2017 Optical Society of America. Quality of a refractive compound X-ray lens can be limited by imperfections in surfaces of unit lenses and stacking precision. In general case both the lens transmission and optical aberrations define properties of a beam in the lens exit plane; together they can be expressed in terms of the generalized pupil function. In this work we measure this function for a diamond single crystal compound refractive lens. Consequently, we apply the pupil function to evaluate the performance of the examined compound refractive X-ray lens. A number of practically important conclusions can be drawn from such analysis.

Aggleton R. et al.

in 2017 27th International Conference on Field Programmable Logic and Applications, FPL 2017 (2017), 8056825. DOI:10.23919/FPL.2017.8056825

Abstract

© 2017 Ghent University. The Compact Muon Solenoid (CMS) experiment at CERN is scheduled for a major upgrade in the next decade in order to meet the demands of the new High Luminosity Large Hadron Collider. Amongst others, a new tracking system is under development including an outer tracker capable of rejecting low transverse momentum particles by looking at the coincidences of hits (stubs) in two closely spaced sensor layers in the same tracker module. Accepted stubs are transmitted off-detector for further processing at 40 MHz. In order to maintain under the increased luminosity the Level-1 trigger rate at 750 kHz, tracker data need to be included in the decision making process. For this purpose, a system architecture has to be developed that will be able to identify particles with transverse momentum above 3 GeV/c by building tracks out of stubs, while achieving an overall processing latency of maximum 4us. Targeting these requirements the current paper presents an FPGA-based track finding architecture that identifies track candidates in real-time and bases its functionality on a fully time-multiplexed approach. As a proof of concept, a hardware system has been assembled targeting the MP7 MicroTCA processing card that features a Xilinx Virtex-7 FPGA, demonstrating a realistic slice of the track finder. The paper discusses the algorithms’ implementation and the efficient utilisation of the available FPGA resources, it outlines the system architecture, and presents some of the hardware demonstrator results.

Schmelzle S., Heethoff M., Heuveline V., Losel P., Becker J., Beckmann F., Schluenzen F., Hammel J.U., Kopmann A., Mexner W., Vogelgesang M., Jerome N.T., Betz O., Beutel R., Wipfler B., Blanke A., Harzsch S., Hornig M., Baumbach T., Van De Kamp T.

in Proceedings of SPIE – The International Society for Optical Engineering, 10391 (2017), 103910P. DOI:10.1117/12.2275959

Abstract

© 2017 SPIE. Beamtime and resulting SRμCT data are a valuable resource for researchers of a broad scientific community in life sciences. Most research groups, however, are only interested in a specific organ and use only a fraction of their data. The rest of the data usually remains untapped. By using a new collaborative approach, the NOVA project (Network for Online Visualization and synergistic Analysis of tomographic data) aims to demonstrate, that more efficient use of the valuable beam time is possible by coordinated research on different organ systems. The biological partners in the project cover different scientific aspects and thus serve as model community for the collaborative approach. As proof of principle, different aspects of insect head morphology will be investigated (e.g., biomechanics of the mouthparts, and neurobiology with the topology of sensory areas). This effort is accomplished by development of advanced analysis tools for the ever-increasing quantity of tomographic datasets. In the preceding project ASTOR, we already successfully demonstrated considerable progress in semi-automatic segmentation and classification of internal structures. Further improvement of these methods is essential for an efficient use of beam time and will be refined in the current NOVAproject. Significant enhancements are also planned at PETRA III beamline p05 to provide all possible contrast modalities in x-ray imaging optimized to biological samples, on the reconstruction algorithms, and the tools for subsequent analyses and management of the data. All improvements made on key technologies within this project will in the long-term be equally beneficial for all users of tomography instrumentations.

Karpov D., Liu Z., Rolo T.D.S., Harder R., Balachandran P.V., Xue D., Lookman T., Fohtung E.

in Nature Communications, 8 (2017), 280. DOI:10.1038/s41467-017-00318-9

Abstract

© 2017 The Author(s). Topological defects of spontaneous polarization are extensively studied as templates for unique physical phenomena and in the design of reconfigurable electronic devices. Experimental investigations of the complex topologies of polarization have been limited to surface phenomena, which has restricted the probing of the dynamic volumetric domain morphology in operando. Here, we utilize Bragg coherent diffractive imaging of a single BaTiO3 nanoparticle in a composite polymer/ferroelectric capacitor to study the behavior of a three-dimensional vortex formed due to competing interactions involving ferroelectric domains. Our investigation of the structural phase transitions under the influence of an external electric field shows a mobile vortex core exhibiting a reversible hysteretic transformation path. We also study the toroidal moment of the vortex under the action of the field. Our results open avenues for the study of the structure and evolution of polar vortices and other topological structures in operando in functional materials under cross field configurations.

Rota, Lorenzo

PhD thesis, Faculty of Electrical Engineering and Information Technology, Karlsruhe Institute of Technology, 2017.

Abstract

In modern particle accelerators, a precise control of the particle beam is essential for the correct operation of the facility. The experimental observation of the beam behavior relies on dedicated techniques, which are often described by the term “beam diagnostics”. Cutting-edge beam diagnostics systems, in particular several experimental setups currently installed at KIT’s synchrotron light source ANKA, employ line scan detectors to characterize and monitor the beam parameters precisely. Up to now, the experimental resolution of these setups has been limited by the line rate of existing detectors, which is limited to a few hundreds of kHz.

This thesis addresses this limitation with the development a novel line scan detector system named KALYPSO – KArlsruhe Linear arraY detector for MHz rePetition-rate SpectrOscopy. The goal is to provide scientists at ANKA with a complete detector system which will enable real-time measurements at MHz repetition rates. The design of both front-end and back-end electronics suitable for beam diagnostic experiments is a challenging task, because the detector must achieve low-noise performance at high repetition rates and with a large number of channels. Moreover, the detector system must sustain continuous data taking and introduce low-latency. To meet these stringent requirements, several novel components have been developed by the author of this thesis, such as a novel readout ASIC and a high-performance DAQ system.

The front-end ASIC has been designed to readout different types of microstrip sensors for the detection of visible and near-infrared light. The ASIC is composed of 128 analog channels which are operated in parallel, plus additional mixed-signal stages which interface external devices. Each channel consists of a Charge Sensitive Amplifier (CSA), a Correlated Double Sampling (CDS) stage and a channel buffer. Moreover, a high-speed output driver has been implemented to interface directly an off-chip ADC. The first version of the ASIC with a reduced number of channels has been produced in a 110 nm CMOS technology. The chip is fully functional and achieves a line rate of 12 MHz with an equivalent noise charge of 417 electrons when connected to a detector capacitance of 1.3 pF.

Moreover, a dedicated DAQ system has been developed to connect directly FPGA readout cards and GPU computing nodes. The data transfer is handled by a novel DMA engine implemented on FPGA. The performance of the DMA engine compares favorably with the current state-of-the-art, achieving a throughput of more than 7 GB/s and latencies as low as 2 us. The high-throughput and low-latency performance of the DAQ system enables real-time data processing on GPUs, as it has been demonstrated with extensive measurements. The DAQ system is currently integrated with KALYPSO and with other detector systems developed at the Institute for Data Processing and Electronics (IPE).

In parallel with the development of the ASIC, a first version of the KALYPSO detector system has been produced. This version is based on a Si or InGaAs microstrip sensor with 256 channels and on the GOTTHARD chip. A line rate of 2.7 MHz has been achieved, and experimental measurements have established KALYPSO as a powerful line scan detector operating at high line rates. The final version of the KALYPSO detector system, which will achieve a line rate of 10 MHz, is anticipated for early 2018.

Finally, KALYPSO has been installed at two different experimental setups at ANKA during several commissioning campaigns. The KALYPSO detector system allowed scientists to observe the beam behavior with unprecedented experimental resolution. First exciting and widely recognized scientific results were obtained at ANKA and at the European XFEL, demonstrating the benefits brought by the KALYPSO detector system in modern beam diagnostics.

 

First assessor: Prof. Dr. M. Weber
Second assessor: Prof. Dr.-Ing. Dr. h.c. J. Becker

Adam W. et al.

in Journal of Instrumentation, 12 (2017), P06018. DOI:10.1088/1748-0221/12/06/P06018

Abstract

© 2017 CERN for the benefit of the CMS collaboration.The upgrade of the LHC to the High-Luminosity LHC (HL-LHC) is expected to increase the LHC design luminosity by an order of magnitude. This will require silicon tracking detectors with a significantly higher radiation hardness. The CMS Tracker Collaboration has conducted an irradiation and measurement campaign to identify suitable silicon sensor materials and strip designs for the future outer tracker at the CMS experiment. Based on these results, the collaboration has chosen to use n-in-p type silicon sensors and focus further investigations on the optimization of that sensor type. This paper describes the main measurement results and conclusions that motivated this decision.

Gentsos C., Fedi G., Magazzu G., Magalotti D., Modak A., Storchi L., Palla F., Bilei G.M., Biesuz N., Chowdhury S.R., Crescioli F., Checcucci B., Tcherniakhovski D., Galbit G.C., Baulieu G., Balzer M.N., Sander O., Viret S., Servoli L., Nikolaidis S.

in 2017 6th International Conference on Modern Circuits and Systems Technologies, MOCAST 2017 (2017), 7937676. DOI:10.1109/MOCAST.2017.7937676

Abstract

© 2017 IEEE. The increase of the luminosity in the High Luminosity upgrade of the CERN Large Hadron Collider (HL-LHC) will require the use of Tracker information in the evaluation of the Level-1 trigger in order to keep the trigger rate acceptable (i.e.: <1MHz). In order to extract the track information within the latency constraints (<5μs), a custom real-time system is necessary. We developed a prototype of the main building block of this system, the Pattern Recognition Mezzanine (PRM) that combines custom Associative Memory ASICs with modern FPGA devices. The architecture, functionality and test results of the PRM are described in the present work.

Onelli O.D., Kamp T.V.D., Skepper J.N., Powell J., Rolo T.D.S., Baumbach T., Vignolini S.

in Scientific Reports, 7 (2017), 1373. DOI:10.1038/s41598-017-01496-8

Abstract

© 2017 The Author(s). Structural colours in living organisms have been observed and analysed in a large number of species, however the study of how the micro- A nd nano-scopic natural structures responsible of such colourations develop has been largely ignored. Understanding the interplay between chemical composition, structural morphology on multiple length scales, and mechanical constraints requires a range of investigation tools able to capture the different aspects of natural hierarchical architectures. Here, we report a developmental study of the most widespread strategy for structural colouration in nature: The cuticular multilayer. In particular, we focus on the exoskeletal growth of the dock leaf beetle Gastrophysa viridula, capturing all aspects of its formation: The macroscopic growth is tracked via synchrotron microtomography, while the submicron features are revealed by electron microscopy and light spectroscopy combined with numerical modelling. In particular, we observe that the two main factors driving the formation of the colour-producing multilayers are the polymerization of melanin during the ecdysis and the change in the layer spacing during the sclerotisation of the cuticle. Our understanding of the exoskeleton formation provides a unique insight into the different processes involved during metamorphosis.

Mohr H., Dritschler T., Ardila L.E., Balzer M., Caselle M., Chilingaryan S., Kopmann A., Rota L., Schuh T., Vogelgesang M., Weber M.

in Journal of Instrumentation, 12 (2017), C04019. DOI:10.1088/1748-0221/12/04/C04019

Abstract

© 2017 IOP Publishing Ltd and Sissa Medialab srl. In this work, we investigate the use of GPUs as a way of realizing a low-latency, high-throughput track trigger, using CMS as a showcase example. The CMS detector at the Large Hadron Collider (LHC) will undergo a major upgrade after the long shutdown from 2024 to 2026 when it will enter the high luminosity era. During this upgrade, the silicon tracker will have to be completely replaced. In the High Luminosity operation mode, luminosities of 5-7 × 1034 cm-2s-1 and pileups averaging at 140 events, with a maximum of up to 200 events, will be reached. These changes will require a major update of the triggering system. The demonstrated systems rely on dedicated hardware such as associative memory ASICs and FPGAs. We investigate the use of GPUs as an alternative way of realizing the requirements of the L1 track trigger. To this end we implemeted a Hough transformation track finding step on GPUs and established a low-latency RDMA connection using the PCIe bus. To showcase the benefits of floating point operations, made possible by the use of GPUs, we present a modified algorithm. It uses hexagonal bins for the parameter space and leads to a more truthful representation of the possible track parameters of the individual hits in Hough space. This leads to fewer duplicate candidates and reduces fake track candidates compared to the regular approach. With data-transfer latencies of 2 μs and processing times for the Hough transformation as low as 3.6 μs, we can show that latencies are not as critical as expected. However, computing throughput proves to be challenging due to hardware limitations.

Kaever P., Balzer M., Kopmann A., Zimmer M., Rongen H.

in Journal of Instrumentation, 12 (2017), C04004. DOI:10.1088/1748-0221/12/04/C04004

Abstract

© 2017 IOP Publishing Ltd and Sissa Medialab srl. Various centres of the German Helmholtz Association (HGF) started in 2012 to develop a modular data acquisition (DAQ) platform, covering the entire range from detector readout to data transfer into parallel computing environments. This platform integrates generic hardware components like the multi-purpose HGF-Advanced Mezzanine Card or a smart scientific camera framework, adding user value with Linux drivers and board support packages. Technically the scope comprises the DAQ-chain from FPGA-modules to computing servers, notably frontend-electronics-interfaces, microcontrollers and GPUs with their software plus high-performance data transmission links. The core idea is a generic and component-based approach, enabling the implementation of specific experiment requirements with low effort. This so called DTS-platform will support standards like MTCA.4 in hard- and software to ensure compatibility with commercial components. Its capability to deploy on other crate standards or FPGA-boards with PCI express or Ethernet interfaces remains an essential feature. Competences of the participating centres are coordinated in order to provide a solid technological basis for both research topics in the Helmholtz Programme “Matter and Technology”: “Detector Technology and Systems” and “Accelerator Research and Development”. The DTS-platform aims at reducing costs and development time and will ensure access to latest technologies for the collaboration. Due to its flexible approach, it has the potential to be applied in other scientific programs.