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Search Results: 1 - 10 of 461886 matches for " A. Zoglauer "
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Submillimeter nuclear medical imaging with a Compton Camera using triple coincidences of collinear β+ annihilation photons and γ-rays
C. Lang,D. Habs,P. G. Thirolf,A. Zoglauer
Physics , 2012,
Abstract: Modern PET systems reach a spatial resolution of 3-10 mm. A disadvantage of this technique is the diffusion of the positron before its decay with a typical range of ca. 1 mm (depending on its energy). This motion and Compton scattering of the 511 keV photons within the patient limit the performance of PET. We present a nuclear medical imaging technique, able to reach submillimeter spatial resolution in 3 dimensions with a reduced activity application compared to conventional PET. This 'gamma-PET' technique draws on specific positron sources simultaneously emitting an additional photon with the \beta+ decay. Exploiting the triple coincidence between the positron annihilation and the third photon, it is possible to separate the reconstructed 'true' events from background. In order to test the feasibility of this technique, Monte-Carlo simulations and image reconstruction has been performed. The spatial resolution amounts to 0.2 mm (FWHM) in each direction, surpassing the performance of conventional PET by about an order of magnitude. The simulated detector geometry exhibits a coincidence detection efficiency of 1.92e-7 per decay. Starting with only 0.7 MBq of source activity (ca. 200-500 times less compared to conventional PET) an exposure time of 450 s is sufficient for source reconstruction.
Recent Developments on PIXE Simulation with Geant4
M. G. Pia,G. Weidenspointner,M. Augelli,L. Quintieri,P. Saracco,M. Sudhakar,A. Zoglauer
Physics , 2009,
Abstract: Particle induced X-ray emission (PIXE) is an important physical effect that is not yet adequately modelled in Geant4. This paper provides a critical analysis of the problem domain associated with PIXE simulation and describes a set of software developments to improve PIXE simulation with Geant4. The capabilities of the developed software prototype are illustrated and applied to a study of the passive shielding of the X-ray detectors of the German eROSITA telescope on the upcoming Russian Spectrum-X-Gamma space mission.
New models for PIXE simulation with Geant4
M. G. Pia,G. Weidenspointner,M. Augelli,L. Quintieri,P. Saracco,M. Sudhakar,A. Zoglauer
Physics , 2010, DOI: 10.1088/1742-6596/219/3/032018
Abstract: Particle induced X-ray emission (PIXE) is a physical effect that is not yet adequately modelled in Geant4. The current status as in Geant4 9.2 release is reviewed and new developments are described. The capabilities of the software prototype are illustrated in application to the shielding of the X-ray detectors of the eROSITA telescope on the upcoming Spectrum-X-Gamma space mission.
Development of Silicon Strip Detectors for a Medium Energy Gamma-ray Telescope
P. F. Bloser,F. Schopper,R. Andritschke,G. Kanbach,A. Zoglauer,P. Lechner
Physics , 2003, DOI: 10.1016/S0168-9002(03)01897-7
Abstract: We report on the design, production, and testing of advanced double-sided silicon strip detectors under development at the Max-Planck-Institute as part of the Medium Energy Gamma-ray Astronomy (MEGA) project. The detectors are designed to form a stack, the "tracker," with the goal of recording the paths of energetic electrons produced by Compton-scatter and pair-production interactions. Each layer of the tracker is composed of a 3 x 3 array of 500 micron thick silicon wafers, each 6 cm x 6 cm and fitted with 128 orthogonal p and n strips on opposite sides (470 micron pitch). The strips are biased using the punch-through principle and AC-coupled via metal strips separated from the strip implant by an insulating oxide/nitride layer. The strips from adjacent wafers in the 3 x 3 array are wire-bonded in series and read out by 128-channel TA1.1 ASICs, creating a total 19 cm x 19 cm position-sensitive area. At 20 degrees C a typical energy resolution of 15-20 keV FWHM, a position resolution of 290 microns, and a time resolution of ~1 microsec is observed.
The MEGA Advanced Compton Telescope Project
P. F. Bloser,R. Andritschke,G. Kanbach,V. Schoenfelder,F. Schopper,A. Zoglauer,for the MEGA Collaboration
Physics , 2001, DOI: 10.1016/S1387-6473(02)00209-9
Abstract: The goal of the Medium Energy Gamma-ray Astronomy (MEGA) telescope is to improve sensitivity at medium gamma-ray energies (0.4-50 MeV) by at least an order of magnitude over that of COMPTEL. This will be achieved with a new compact design that allows for a very wide field of view, permitting a sensitive all-sky survey and the monitoring of transient and variable sources. The key science objectives for MEGA include the investigation of cosmic high-energy particle accelerators, studies of nucleosynthesis sites using gamma-ray lines, and determination of the large-scale structure of galactic and cosmic diffuse background emission. MEGA records and images gamma-ray events by completely tracking both Compton and pair creation interactions in a tracker of double-sided silicon strip detectors and a calorimeter of CsI crystals able to resolve in three dimensions. We present initial laboratory calibration results from a small prototype MEGA telescope.
Radioactive decay simulation with Geant4: experimental benchmarks and developments for X-ray astronomy applications
S. Hauf,M. Kuster,Dieter H. H. Hoffmann,Z. W. Bell,M. G. Pia,Georg Weidenspointner,A. Zoglauer
Physics , 2010,
Abstract: We present {\gamma} spectroscopy validation measurements for the Geant4 radioactive decay simulation for a selected range of isotopes using a simple experimental setup. Using these results we point out problems in the decay simulation and where they may originate from.
Polarization studies with NuSTAR
Simone Lotti,Lorenzo Natalucci,Paolo Giommi,B. Grefenstette,Fiona A. Harrison,Kristin K. Madsen,Matteo Perri,Simonetta Puccetti,Andreas Zoglauer
Physics , 2012, DOI: 10.1117/12.925989
Abstract: The capability of NuSTAR to detect polarization in the Compton scattering regime (>50 keV) has been investigated. The NuSTAR mission, flown on June 2012 a Low Earth Orbit (LEO), provides a unique possibility to confirm the findings of INTEGRAL on the polarization of cosmic sources in the hard X-rays. Each of the two focal plane detectors are high resolution pixellated CZT arrays, sensitive in the energy range ~ 3 - 80 keV. These units have intrinsic polarization capabilities when the proper information on the double events is transmitted on ground. In this case it will be possible to detect polarization from bright sources on timescales of the order of 10^5s
Research in Geant4 electromagnetic physics design, and its effects on computational performance and quality assurance
M. Augelli,M. Begalli,S. Hauf,C. H. Kim,M. Kuster,M. G. Pia,P. Queiroz Filho,L. Quintieri,P. Saracco,D. Souza Santos,G. Weidenspointner,A. Zoglauer
Physics , 2009,
Abstract: The Geant4 toolkit offers a rich variety of electromagnetic physics models; so far the evaluation of this Geant4 domain has been mostly focused on its physics functionality, while the features of its design and their impact on simulation accuracy, computational performance and facilities for verification and validation have not been the object of comparable attention yet, despite the critical role they play in many experimental applications. A new project is in progress to study the application of new design concepts and software techniques in Geant4 electromagnetic physics, and to evaluate how they can improve on the current simulation capabilities. The application of a policy-based class design is investigated as a means to achieve the objective of granular decomposition of processes; this design technique offers various advantages in terms of flexibility of configuration and computational performance. The current Geant4 physics models have been re-implemented according to the new design as a pilot project. The main features of the new design and first results of performance improvement and testing simplification are presented; they are relevant to many Geant4 applications, where computational speed and the containment of resources invested in simulation production and quality assurance play a critical role.
Inter-Comparison and Validation of Geant4 Photon Interaction Models
M. Augelli,M. Begalli,M. G. Pia,P. P. Queiroz,L. Quintieri,D. Souza-Santos,M. Sudhakar,P. Saracco,G. Weidenspointner,A. Zoglauer
Physics , 2009,
Abstract: A R&D project, named Nano5, has been recently launched to study an architectural design in view of addressing new experimental issues related to particle transport in high energy physics and other related physics disciplines with Geant4. In this frame, the first step has involved the redesign of the photon interaction models currently available in Geant4; this task has motivated a thorough investigation of the physics and computational features of these models, whose first results are presented here.
Quantifying the unknown: issues in simulation validation and their experimental impact
M. G. Pia,M. Batic,G. Hoff,P. Saracco,M. Begalli,M. Han,C. H Kim,H. Seo,S. Hauf,M. Kuster,L. Quintieri,G. Weidenspointner,A. Zoglauer
Physics , 2011,
Abstract: The assessment of the reliability of Monte Carlo simulations is discussed, with emphasis on uncertainty quantification and the related impact on experimental results. Methods and techniques to account for epistemic uncertainties, i.e. for intrinsic knowledge gaps in physics modeling, are discussed with the support of applications to concrete experimental scenarios. Ongoing projects regarding the investigation of epistemic uncertainties in the Geant4 simulation toolkit are reported.
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