Ändra sökning
Avgränsa sökresultatet
1 - 21 av 21
RefereraExporteraLänk till träfflistan
Permanent länk
Referera
Referensformat
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Annat format
Fler format
Språk
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Annat språk
Fler språk
Utmatningsformat
  • html
  • text
  • asciidoc
  • rtf
Träffar per sida
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sortering
  • Standard (Relevans)
  • Författare A-Ö
  • Författare Ö-A
  • Titel A-Ö
  • Titel Ö-A
  • Publikationstyp A-Ö
  • Publikationstyp Ö-A
  • Äldst först
  • Nyast först
  • Skapad (Äldst först)
  • Skapad (Nyast först)
  • Senast uppdaterad (Äldst först)
  • Senast uppdaterad (Nyast först)
  • Disputationsdatum (tidigaste först)
  • Disputationsdatum (senaste först)
  • Standard (Relevans)
  • Författare A-Ö
  • Författare Ö-A
  • Titel A-Ö
  • Titel Ö-A
  • Publikationstyp A-Ö
  • Publikationstyp Ö-A
  • Äldst först
  • Nyast först
  • Skapad (Äldst först)
  • Skapad (Nyast först)
  • Senast uppdaterad (Äldst först)
  • Senast uppdaterad (Nyast först)
  • Disputationsdatum (tidigaste först)
  • Disputationsdatum (senaste först)
Markera
Maxantalet träffar du kan exportera från sökgränssnittet är 250. Vid större uttag använd dig av utsökningar.
  • 1. Aykac, M.
    et al.
    Bauer, F.
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Williams, C.W.
    Loope, M.
    Schmand, M.
    Timing performance of Hi-Rez detector for time-of-flight (TOF) PET2006Ingår i: IEEE Transactions on Nuclear Science, ISSN 0018-9499, E-ISSN 1558-1578, Vol. 53, nr 3, s. 1084-1089Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Positron emission tomography (PET)-based on time-of-flight (TOF) is desired to enhance the image quality by improving the noise variance in the reconstruction. This benchtop study evaluates the timing performance of the current Hi-Rez detector which is based on a 13/spl times/13 LSO array of 4 mm/spl times/4 mm/spl times/20 mm crystals and not optimized for TOF PET applications. A Hamamatsu R9779, fast, 51-mm-diameter PMT was used for some experiments in this study as a reference PMT and its time resolution was measured to be 160 ps with a plastic scintillator. The average crystal time resolution of two Hi-Rez detectors, coupled to a 2/spl times/2 array of Hamamatsu 25-mm-diameter R8619 PMTs at +1050 V, in coincidence was measured to be 733 ps. The average crystal energy resolutions for two detectors were measured 13.1% and 13.2%. The average crystal time resolution of two Hi-Rez detectors improved from 733 ps to 642 ps when the PMT voltage was increased to +1300 V. The Hi-Rez detector was originally optimized for good energy resolution to reduce scatter and high packing fraction to obtain high sensitivity and improved spatial resolution for clinical PET.

  • 2.
    Bauer, F.
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Aykac, M.
    Loope, M.
    Williams, C. W.
    Eriksson, L.
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Schmand, M.
    Performance Study of the New Hamamatsu R9779 and Photonis XP20D0 Fast 2" Photomultipliers2007Ingår i: IEEE Transactions on Nuclear Science, ISSN 0018-9499, E-ISSN 1558-1578, Vol. 54, nr 3, s. 422-426Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The focus of this paper is the evaluation of the new fast 51 mm-diameter, 8-stage Hamamatsu R9779 photomultipliers (PMTs) with an acceleration-ring at the front-end and the Photonis XP20D0 PMTs with a screening grid in front of the anode. The following performance characteristics are presented: Timing resolution, anode-scan-uniformity and transit-time spread. The unfolded timing resolution for two R9779 was 192 ps and 210 ps using plastic scintillators. The individual timing resolutions for two XP20D0 using plastic scintillators are 181 ps and 154 ps, respectively. The variation in time resolution across the windows of the two R9779 ranged between 117 ps and 171 ps, and 79 ps and 73 ps for the two XP20D0 PMTs.

  • 3.
    Bauer, F.
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Corbeil, J.
    Schmand, M.
    Henseler, D.
    Measurements and Ray-Tracing Simulations of Light Spread in LSO Crystals2009Ingår i: IEEE Transactions on Nuclear Science, ISSN 0018-9499, E-ISSN 1558-1578, Vol. 56, nr 5, s. 2566-2573Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We report on measurements of the absolute light output from LSO crystals for irradiation with 511 keV gamma rays as a function of interaction position, reflector arrangement, detector coupling geometry and optical coupling to an adjacent crystal. The light output for this series of geometrical configurations is simulated with the ZEMAX ray-tracing software. By fine-tuning the optical parameters of the bulk and at the interfaces of the crystal, a model is obtained which yields good agreement with experimental data for all configurations. The resulting parameter set is applied to calculate the light distribution in a 12$,times,$ 12 crystal block detector. A comparison of measured and calculated block position profiles shows good agreement, demonstrating the potential of the simulation model to predict block detector performance data and provide guidelines for future array designs.

  • 4.
    Bauer, F.
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Zhang, N.
    Schmand, M.
    Loope, M.
    Eriksson, L.
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Aykac, M.
    Dynode-Timing Method for PET Block Detectors2008Ingår i: IEEE Transactions on Nuclear Science, ISSN 0018-9499, E-ISSN 1558-1578, Vol. 55, nr 1, s. 451-456Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The focus of this paper is the investigation of a new dynode-timing technique optimized for PET block detectors. This method allows utilization of dynode signals from single but especially multiple photo-multiplier tubes (PMTs), operated with negative high-voltage. The technique will provide an event-timing trigger without deteriorating the anode signal. A printed circuit board has been developed and built for this investigation. Benchmark measurements have been performed, comparing timing of the anode signal with timing of the inverted last-dynode signal and timing of the dynode signal extracted via a newly developed LVPECL-logic based board. Timing measurements were performed with plastic as well as LSO scintillators. From single PMT measurements we find a 30 ps improvement with the dynode-timing method compared to the standard anode timing with two Photonis XP2020Q PMTs with LSO (10 mmtimes10 mmtimes10 mm). For a quad-PMT block detector, assembled of four Hamamatsu R9800 with a Hi-Rez block, the timing-resolution improves ~10%, by 43 ps compared to the standard anode timing.

  • 5.
    Bauer, Florian
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Aykac, Mehmet
    Eriksson, Lars
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Schmand, Matthias
    Depth of interaction with a 3-dimensional checkerboard arrangement LSO-LSO block2010Ingår i: IEEE Transactions on Nuclear Science, ISSN 0018-9499, E-ISSN 1558-1578, Vol. 57, nr 3, s. 971-975Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In order to improve image quality in Positron Emission Tomography (PET) different routes are being pursued such as fast timing resolution for time-of-flight PET, higher spatial resolution by the use of smaller scintillator pixels and the use of depth-of-interaction information. The detection of the depth-of-interaction (DOI) of a gamma ray within a detector, deploying pulse shape discrimination (PSD), has been used to increase sensitivity and spatial resolution, especially at the edge of the field of view (FOV). The DOI information is used to reduce the parallax error; thus improving spatial resolution. Commonly, different scintillator materials with different decay times and light output and other differentiating factors, such as density, emission spectra, etc. are used for DOI detectors. We present a multi-layer phoswich detector comprised of LSO with different decay times in the range from 30 ns to 47 ns. The difference in decay times is achieved by co-doping LSO:Ce with Ca, resulting in short decay times of ~ 30 ns [1]. The use of a cut light guide allows the use of regular Photomultiplier tubes, giving the opportunity of a potential DOI detector replacement for current detectors. We were able to identify each pixel in the different detector layers

  • 6.
    Bohm, Christian
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Hellman, Sten
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Hidvegi, Attila
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Silverstein, Samuel
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    ATLAS Level-1 Calorimeter Trigger: Subsystem Tests of a Jet/Energy-sum Processor Module2004Ingår i: IEEE Transactions on Nuclear Science, ISSN 0018-9499, E-ISSN 1558-1578, Vol. 51, nr 5, s. 2356-2361Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The ATLAS Level-1 Calorimeter Trigger consists of a Preprocessor, a Cluster Processor (CP), and a Jet/Energy-sum Processor (JEP). The CP and JEP receive digitized trigger-tower data from the Preprocessor and produce trigger multiplicities and total and missing energy for the final trigger decision. The trigger also provides region-of-interest information for the Level-2 trigger and intermediate results of the data acquisition system for monitoring and diagnostics by using Readout Driver modules. The JEP identifies and localizes jets, and sums total and missing transverse energy information from the trigger data. The Jet/Energy Module (JEM) is the main module of the JEP. The JEM prototype is designed to be functionally identical to the final production module for ATLAS and to have the full number of channels. Three JEM prototypes have been built and successfully tested. Various test vector patterns were used to test the energy summation and the jet algorithms. Data communication between adjacent JEMs and all other relevant modules of the JEP has been tested. Recent test results using the JEM prototypes are discussed.

  • 7.
    Bohm, Christian
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Hellman, Sten
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Hidvegi, Attila
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Silverstein, Samuel
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Pre-Production Validation of the ATLAS Level-1 Calorimeter Trigger System2006Ingår i: IEEE Transactions on Nuclear Science, ISSN 0018-9499, E-ISSN 1558-1578, Vol. 53, nr 3, s. 859-863Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The Level-1 Calorimeter Trigger is a major part of the first stage of event selection for the ATLAS experiment at the LHC. It is a digital, pipelined system with several stages of processing, largely based on FPGAs, which perform programmable algorithms in parallel with a fixed latency to process about 300 Gbyte/s of input data. The real-time output consists of counts of different types of trigger objects and energy sums. Prototypes of all module types have been undergoing intensive testing before final production during 2005. Verification of their correct operation has been performed stand-alone and in the ATLAS test-beam at CERN. Results from these investigations will be presented, along with a description of the methodology used to perform the tests.

  • 8.
    Bohm, Christian
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Hellman, Sten
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Hidvegi, Attila
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Silverstein, Samuel
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    The ATLAS Level-1 Calorimeter Trigger Architecture2004Ingår i: IEEE Transactions on Nuclear Science, ISSN 0018-9499, E-ISSN 1558-1578, Vol. 51, nr 3, s. 356-360Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The architecture of the ATLAS Level-1 Calorimeter Trigger system (L1Calo) is presented. Common approaches have been adopted for data distribution, result merging, readout, and slow control across the three different subsystems. A significant amount of common hardware is utilized, yielding substantial savings in cost, spares, and development effort. A custom, high-density backplane has been developed with data paths suitable for both the em/τ cluster processor (CP) and jet/energy-summation processor (JEP) subsystems. Common modules also provide interfaces to VME, CANbus and the LHC timing, trigger and control system (TTC). A common data merger module (CMM) uses field-programmable gate arrays (FPGAs) with multiple configurations for summing electron/photon and τ/hadron cluster multiplicities, jet multiplicities, or total and missing transverse energy. The CMM performs both crate- and system-level merging. A common, FPGA-based readout driver (ROD) is used by all of the subsystems to send input, intermediate and output data to the data acquisition (DAQ) system, and region-of-interest (RoI) data to the level-2 triggers. Extensive use of FPGAs throughout the system makes the trigger flexible and upgradable, and several architectural choices have been made to reduce the number of intercrate links and make the hardware more robust.

  • 9.
    Bousselham, Abdel Kader
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Bohm, Christian
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Sampling pulses for optimal timing2007Ingår i: IEEE Transactions on Nuclear Science, ISSN 0018-9499, E-ISSN 1558-1578, Vol. 54, nr 2, s. 320-326Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    When extracting unknown band-limited pulses from sampled data, the Nyquist criterion defines the minimum sampling frequency. With well-defined pulse shapes and a stationary noise environment one can use matched filters to recover time and amplitude, but this is usually not the case with scintillation detectors. If the noise is not stationary other methods must be used. Our study investigates different timing strategies and how the timing precision depends on ADC resolution and sample rate. It also compares the timing precision with data obtained from an analogue setup. Pulses from an LSO crystal with photomultiplier readout are studied experimentally. Our best method gives in this case a 10% improvement in timing compared to a matched filter approach. Some simulation results are also reported

  • 10. Conti, Maurizio
    et al.
    Eriksson, Lars
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Westerwoudt, Victor
    Estimating Image Quality for Future Generations of TOF PET Scanners2013Ingår i: IEEE Transactions on Nuclear Science, ISSN 0018-9499, E-ISSN 1558-1578, Vol. 60, nr 1, s. 87-94Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Images taken with time-of-flight (TOF) positron emission tomography (PET) scanners are of improved quality compared to equivalent non-TOF images. This improvement is dependent on the scanner time resolution. The present generation of commercial TOF scanners has a time resolution in the range of 500-600 ps full width half maximum. In this work we investigate how the image characteristics will improve for future generations of TOF PET. We performed a Geant4 simulation of a 30-cm uniform cylinder containing hot spheres, with time resolution ranging from 600 to 200 ps. Data were reconstructed using TOF filtered back projection (FBP) and TOF ordered subsets expectation maximization (OSEM), with nonTOF reconstruction as a reference. Images were compared in terms of contrast recovery and variance in the image. The TOF gain was evaluated for both reconstruction methods. The TOF gain was also evaluated vs. counts in the scan, in order to understand the behavior of such gain at very low statistics. Using TOF FBP, it was shown that the TOF gain can be used as a sensitivity amplifier, reducing (according to the expected TOF gain) the number of counts necessary to produce an image of the same characteristics. Some limitations in the TOF gain were observed at very low counts, particularly if using iterative methods.

  • 11.
    Eriksson, Lars
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Conti, M.
    Melcher, C. L.
    Townsend, D. W.
    Eriksson, M.
    Rothfuss, H.
    Casey, M. E.
    Bendriem, B.
    Towards Sub-Minute PET Examination Times2011Ingår i: IEEE Transactions on Nuclear Science, ISSN 0018-9499, E-ISSN 1558-1578, Vol. 58, nr 1, s. 76-81Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The main performance parameters in positron camera system design are sensitivity and spatial resolution. This paper concerns sensitivity, which is a function of the scintillation material, the solid angle subtended by the detector array, and the scintillator packing fraction. The solid angle can be increased by extending the axial extent of cylindrical detector systems. Most commercial positron camera systems are based on rings of detector blocks with lutetium oxyorthosilicate, LSO:Ce or LYSO:Ce, as the scintillator of choice. By adding more rings, the solid angle and thus the absolute sensitivity increases while the singles detection efficiency remains fairly constant assuming the same crystal thickness. It has been shown that Ca co-doping of LSO:Ce reduces the scintillation decay time to similar to 30 ns with a light output over 30000 ph/MeV. This improvement may give a time-of-flight (TOF) advantage with time resolution of 500 ps or less. If the count rate sensitivity of a large axial field-of-view (AFOV) system is combined with the TOF sensitivity increase, we have the means to create examination times in the sub-minute range with no compromise in image quality. In the present study we have compared the existing Siemens molecular CT (mCT) systems to future 6, 8, 12, 20 and higher block ring systems with and without TOF. The mCT 4 block ring system has been used as a reference. The time for acceptable image quality with this system is then extrapolated to other systems based on planar sensitivity. However, the planar sensitivity is related to the solid angle, and reaches saturation for large AFOVs. This implies that there is an upper count rate sensitivity limit. A 20 block ring system may cover a 70 cm examination range at a certain planar count rate and could provide acceptable quality images in approximately 10 seconds by combining the high planar sensitivity count rate provided by the multi-ring feature, the high stopping power of LSO and the TOF gain due to the improved timing resolution. The increased sensitivity may be used to reduce patient dose.

  • 12.
    Eriksson, Lars
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Conti, M.
    Melcher, C. L.
    Zhuravleva, M.
    Eriksson, M.
    Rothfuss, H.
    LuYAP/LSO Phoswich Detectors for High Resolution Positron Emission Tomography2013Ingår i: IEEE Transactions on Nuclear Science, ISSN 0018-9499, E-ISSN 1558-1578, Vol. 60, nr 1, s. 194-196Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The spatial resolution in positron emission tomography (PET) can be improved by the addition of depth-of-interaction (DOI) information. This can be achieved by using the phoswich approach in which depth identification relies on differences in scintillation decay time and pulse shape discrimination techniques. In this paper we have looked at a special phoswich combination LuAP/LSO or LuYAP/LSO. This combination of scintillators is especially interesting since LuAP and LuYAP have emission in the excitation band of LSO, which may have an impact on the timing resolution of the detector. As will be shown in this paper, the phoswich concept based on these two scintillators can be utilized, however, with some limitations. This paper is an extension of our previous phoswich investigation [3].

  • 13.
    Eriksson, Lars
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för oorganisk kemi och strukturkemi.
    Melcher, Charles L.
    Eriksson, Marita
    Rothfuss, Harold
    Grazioso, Ron
    Aykac, Mehmet
    Design Considerations of Phoswich Detectors for High Resolution Positron Emission Tomography2009Ingår i: IEEE Transactions on Nuclear Science, ISSN 0018-9499, E-ISSN 1558-1578, Vol. 56, nr 1, s. 182-188Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A way to improve the spatial resolution in positron emission tomography (PET) is to determine the depth-of-interaction (DOI) in the detector. A way to achieve this is to use the phoswich approach, a detector with two or more layers of different scintitlators. The layer identification is done by using differences in scintillation decay time and pulse shape discrimination techniques. The advantages of the concept have been demonstrated in the HRRT high resolution PET system using a LSO/LYSO combination giving a high spatial resolution uniformity of around 2.5 mm within a larger part of the imaged volume. A phoswich combination that lately has received attention is LuAP/LSO or LuYAP/LSO. The suggestions come from the Crystal Clear Collaboration and there is a patent application for its use in PET. This particular combination of phoswich may, however, have a complication since both LuAP and LuYAP emit in the excitation band of LSO, thus making the functionality more complex. In the present paper we have looked into this and suggested different ways to overcome potential drawbacks.

  • 14. Hanson, Kael
    et al.
    Robson, Clyde
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Extending the IceCube DAQ System by Integration of the Generic High-Speed Sorter Module TESS2013Ingår i: IEEE Transactions on Nuclear Science, ISSN 0018-9499, E-ISSN 1558-1578, Vol. 60, nr 5, s. 3742-3745Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In the extreme environment of Antarctica at the South Pole, the IceCube experiment, the world's first kilometer-scale neutrino telescope, collects cosmic ray events. IceCube consists of over 5000 digital optical sensor modules (DOMs) deployed on 86 instrumentation lines each extending 2.5 km deep in the antarctic ice. The array of optical modules monitors the Cherenkov light emitted by passing radiation, which, when digitized and timestamped to nanosecond precision, is used as input to sophisticated reconstruction algorithms that determine the direction, energy, and type of the incident cosmic ray event. In order to achieve this goal, the IceCube data acquisition system merges the digital data streams from each photodetector into a single time-ordered list which is presented to online triggers that determine, in realtime, whether or not a given pattern of hits is noise or signal. At the present time, the data provided to the triggers is limited by the performance of sorting and merging algorithms: the 500 Hz raw data rate from each sensor (2.5 MHz array aggregate rate) is beyond the capability of the central sort and merge. The current solution adopted by the IceCube detector is to impose a hardware-based pretrigger coincidence on hits emanating from the DOMs which reduces the rate by a factor of 20. While this pretrigger coincidence has negligible impact on the detector sensitivity for the principal goal of high-energy neutrinos from galactic or extragalactic sources, other low-energy physics searches are affected. This presentation details work done to develop and implement a system, TESS, which is capable of merging the full raw data stream being produced by the IceCube DOMs. TESS is designed as a pipelined architecture with three major modules: server, selector and the client glued together by circular buffers. The three modules runs in only three threads and since the architecture is self synchronizing and uses no data copying maximum performance can be achieved for global sorting of payloads. The TESS sorting architecture was originally designed to provide a globally sorted data stream for triggers targeting low-energy events from annihilation of hypothesized dark-matter particles, however its utility is generalizable to any IceCube trigger which requires inspection of the full data stream. The IceCube online supernova detection system is a notable example. Moreover, the algorithm is generic to any system involving multiple, independently sorted data streams which must be merged into a single sorted data stream.

  • 15.
    Hidvegi, Attila
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Gessler, Patrick
    Deutsches Elektronen-Synchrotron (DESY).
    Rehlich, Kay
    Deutsches Elektronen-Synchrotron (DESY),.
    Bohm, Christian
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Timing and Triggering System Prototype for the XFEL Project2010Ingår i: IEEE Transactions on Nuclear Science, ISSN 0018-9499, E-ISSN 1558-1578, Vol. 58, nr 4, s. 1852-1856Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The European X-ray Free Electron Laser (XFEL) [1] at DESY in Hamburg will begin operating in the next few years, enabling new, ground-breaking research opportunities. The entire system requires very precise clock and trigger distribution, synchronous with the 1.3 GHz system RF-frequency, over distances of more than 3.4 km. The new experiment demanded features that other commercial solutions could not yet provide. Researchers at Stockholm University and DESY have developed a prototype for the timing system of XFEL. It has been decided that XFEL will use modern ATCA and Micro-TCA systems because of their advanced features and reliability. The timing system has been adapted to the Micro-TCA bus standard and also follows the new upcoming xTCA for physics standard. The prototype is fully functional and complete. It will serve as a platform for future development of the whole timing system. This paper describes the hardware design and some test results using the prototype board.

  • 16.
    Kavianipour, Hossein
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Muschter, Steffen
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Bohm, Christian
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    High Performance FPGA-Based DMA Interface for PCIe2014Ingår i: IEEE Transactions on Nuclear Science, ISSN 0018-9499, E-ISSN 1558-1578, Vol. 61, nr 2, s. 745-749Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We present a data communication suite developed for use in the Track Engine Trigger for the IceCube Neutrino Observatory at the South Pole. The suite is applicable to any bidirectional Direct Memory Access (DMA) transfer between FPGA logic and system memory on a host PC via PCIe. The suite contains a DMA controller firmware, test benches, a Linux driver and a user application for DMA and Peripheral Input/Output transfers (PIO) into on-FPGA memory modules and FIFOs. The DMA which is based on the Xilinx' bus master DMA, produces measured transfer speeds up to 748 MB/s (read) and 784 MB/s (write) using the Xilinx VC707 Virtex-7 board. The hardware part of the suite has been verified on different circuit boards with different FPGAs.

  • 17. Szczesniak, T.
    et al.
    Moszynski, M.
    Swiderski, L.
    Nassalski, A.
    Syntfeld-Kazuch, A.
    Ojala, P.
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Bohm, Christian
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    A Time Resolution Study of a Continuous Crystal Detector for TOF PET2010Ingår i: IEEE Transactions on Nuclear Science, ISSN 0018-9499, E-ISSN 1558-1578, Vol. 57, nr 1, s. 40-47Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The majority of current Positron Emission Tomography (PET) systems are based on block-detectors consisting of many scintillating pixels read by a smaller number of photomultipliers (PMTs). An improvement of the time resolution, using a common light readout from a cluster of PMTs, was proposed by Kuhn et al., and tested by us earlier with LSO crystals. This, triggered an idea to design a new PET detector optimized for Time of Flight (TOF) systems, based on continuous crystals. In the present work, we report on optimization of timing with a 20 x 20 x 20 mm(3) LYSO crystal coupled to a 16-channel photomultiplier H8711-200MOD from Hamamatsu. First, measurements were performed of the transit time jitter, the number of photoelectrons and the time resolution using a small 10 x 10 x 5 mm(3) LSO crystal coupled to a H8711-200MOD PMT. Results were compared with data collected from fast timing photomultipliers like Photonis XP1020, XP3060, XP20D0 or Hamamatsu R9800. In the second part of the study, the time resolution measurements and the optimization of the system were made with a continuous LYSO crystal. The final results are discussed in terms of the measured photoelectron number and the requirements for the TOF-PET scanners.

  • 18. Tang, F.
    et al.
    Åkerstedt, Henrik
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Anderson, K.
    Bohm, Christian
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Hildebrand, K.
    Muschter, Steffen
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Oreglia, M.
    Upgrade Analog Readout and Digitizing System for ATLAS TileCal Demonstrator2015Ingår i: IEEE Transactions on Nuclear Science, ISSN 0018-9499, E-ISSN 1558-1578, Vol. 62, nr 3, s. 1045-1049Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The TileCal Demonstrator is a prototype for the future upgrade of the ATLAS hadron calorimeter when the Large Hadron Collider increases luminosity in year 2023 (HL-LHC). It will be used for functionality and performance tests. The Demonstrator has 48 channels of upgraded readout and digitizing electronics and a new digital trigger capability, but is backwards-compatible with the present detector system insofar as it also provides analog trigger signals and can communicate as the present system. The on-detector part of the Demonstrator is comprised of 4 identical mechanical mini-drawers, each equipped with up to 12 photomultipliers (PMTs). The on-detector electronics includes 45 Analog Front-End Boards, each serving an individual PMT; 4 Main Boards, each to control and digitize up to 12 PMT signals, and 4 corresponding high-speed Daughter Boards serving as data hubs between on-detector and off-detector electronics. It is fully compatible with the present system, accepting ATLAS triggers, timing and slow control commands for the data acquisition, detector control, and detector operation monitoring. We plan to insert one fully functional Demonstrator module into the present ATLAS TileCal detector for the LHC RUN 2 in Christmas shutdown in 2015 or 2016.

  • 19. Westerwoudt, Victor
    et al.
    Conti, Maurizio
    Eriksson, Lars
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Advantages of Improved Time Resolution for TOF PET at Very Low Statistics2014Ingår i: IEEE Transactions on Nuclear Science, ISSN 0018-9499, E-ISSN 1558-1578, Vol. 61, nr 1, s. 126-133Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this paper, Monte Carlo generated data are used to simulate a time-of-flight (TOF) positron emission tomography (PET) scanner with improving time resolution, down to 200-ps time resolution. TOF and non-TOF ordered subsets expectation maximization (OSEM) reconstructions were compared in terms of contrast recovery and signal-to-noise ratio, with the purpose of characterizing the differences of TOF and non-TOF at very low counts. This study shows that there is a lower limit to the number of counts in a PET scan, in order to obtain a quantitative PET image. Below this limit, the reliability of the measurement is very poor. The use of TOF information has the beneficial effect of lowering this statistical limit, allowing for shorter reliable PET scans. Another interesting finding derives from the comparison with TOF filtered back projection (FBP) images: if time resolution can be improved, TOF FBP images become competitive with TOF MLEM and OSEM algorithms, not only in terms of contrast recovery but also in terms of reduced noise level.

  • 20. Yang, Kan
    et al.
    Melcher, Charles L.
    Rack, Philip D.
    Eriksson, Lars
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för oorganisk kemi och strukturkemi.
    Effects of Calcium Codoping on Charge Traps in LSO:Ce Crystals2009Ingår i: IEEE Transactions on Nuclear Science, ISSN 0018-9499, E-ISSN 1558-1578, Vol. 56, nr 5, s. 2960-2965Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Experimental studies of Lu2SiO5 : Ce (LSO:Ce) crystals codoped with various concentrations of Ca (0, 0.1, 0.2, 0.3, and 0.4 at% in the melt) are presented. The scintillation and optical properties including photoluminescence decay, emission, excitation, absorption, afterglow and thermoluminescence properties are investigated as a function of Ca concentration. Experimental data show Ca codoping significantly reduces the trapped charge population in the crystal matrix. Hence, the scintillation decay time of LSO:Ce is shortened and the afterglow is suppressed. Thermoluminescence studies show a strong correlation between the integrated thermoluminescence intensity and the Ca concentration.

  • 21.
    Åkerstedt, Henrik
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Muschter, Steffen
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Drake, Gary
    Anderson, Kelby
    Bohm, Christian
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Oreglia, Mark
    Tang, Fukun
    Reliable and Redundant FPGA Based Read-Out Design in the ATLAS TileCal Demonstrator2015Ingår i: IEEE Transactions on Nuclear Science, ISSN 0018-9499, E-ISSN 1558-1578, Vol. 62, nr 5, s. 2129-2133Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The current ATLAS Tile Calorimeter read-out system is scheduled for replacement around 2023 due to old age and higher performance needs. The new proposed system is designed to be radiation tolerant, modular, redundant and reconfigurable. To achieve full detector read-out, Kintex-7 FPGAs from Xilinx will be used, in addition to multiple 10 Gb/s optical read-out links. During 2015/2016, a hybrid demonstrator system including the new read-out system will be installed in one slice of the ATLAS Tile Calorimeter to evaluate the new design. This paper describes different firmware strategies along with their integration in the demonstrator in the context of high reliability protection against hardware malfunction and radiation induced errors.

1 - 21 av 21
RefereraExporteraLänk till träfflistan
Permanent länk
Referera
Referensformat
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Annat format
Fler format
Språk
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Annat språk
Fler språk
Utmatningsformat
  • html
  • text
  • asciidoc
  • rtf