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29 results on '"Stefanescu, Alexander"'

1. Background Simulations of the Wide Field Imager of the ATHENA X-Ray Observatory

Author

Hauf, Steffen, Kuster, Markus, Pia, Maria Grazia, Hoffmann, Dieter H. H., Lang, Philipp, Neff, Stephan, Stefanescu, Alexander, and Strüder, Lothar

Subjects
Astrophysics - Instrumentation and Methods for Astrophysics, Astrophysics - High Energy Astrophysical Phenomena
Abstract

The ATHENA X-ray Observatory-IXO is a planned multinational orbiting X-ray observatory with a focal length of 11.5m. ATHENA aims to perform pointed observations in an energy range from 0.1 keV to 15 keV with high sensitivity. For high spatial and timing resolution imaging and spectroscopic observations the 640x640 pixel^2 large DePFET-technology based Wide field Imager (WFI) focal plane detector, providing a field of view of 18 arcsec will be the main detector. Based on the actual mechanics, thermal and shielding design we present estimates for the WFI cosmic ray induced background obtained by the use of Monte-Carlo simulations and possible background reduction measures., Comment: IEEE NSS MIC Conference 2011, Valencia, Spain

Published
2011
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2. Optical polarisation of the Crab pulsar: precision measurements and comparison to the radio emission

Author

Słowikowska, Agnieszka, Kanbach, Gottfried, Kramer, Michael, and Stefanescu, Alexander

Subjects
Astrophysics - Solar and Stellar Astrophysics
Abstract

The linear polarisation of the Crab pulsar and its close environment was derived from observations with the high-speed photo-polarimeter OPTIMA at the 2.56-m Nordic Optical Telescope in the optical spectral range (400 - 750 nm). Time resolution as short as 11 microseconds, which corresponds to a phase interval of 1/3000 of the pulsar rotation, and high statistics allow the derivation of polarisation details never achieved before. The degree of optical polarisation and the position angle correlate in surprising details with the light curves at optical wavelengths and at radio frequencies of 610 and 1400 MHz. Our observations show that there exists a subtle connection between presumed non-coherent (optical) and coherent (radio) emissions. This finding supports previously detected correlations between the optical intensity of the Crab and the occurrence of giant radio pulses. Interpretation of our observations require more elaborate theoretical models than those currently available in the literature., Comment: 21 pages, 13 figures, uses AMS.sty, mn2e.cls, mn2e.bst and natbib.sty, submitted to MNRAS

Published
2009
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3. ATHENA reference telescope design and recent mission level consolidation

Author

Ferreira, Ivo, primary, Bavdaz, Marcos, additional, Ayre, Mark, additional, Fransen, Sebastiaan, additional, Pacros, Anne, additional, Linder, Martin, additional, Stefanescu, Alexander, additional, Branco, Moritz, additional, Guainazzi, Matteo, additional, Ness, Jan-Uwe, additional, Oosterbroek, Tim, additional, and Willingale, Richard, additional

Published
2021
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6. Contactless suspension for cryogenic applications

Author

NAVARRO ZAFRA, J., VALIENTE-BLANCO, I., SANCHEZ-GARCIA-CASARRUBIOS, J., RODRIGUEZ-CELIS, F., RUIZ-LUCINI, R., PEREZ-DEL-ALAMO, J.L., CRISTACHE, C., ESNOZ-LARRAYA, J., PEREZ-DIAZ, J.L., STEFANESCU, Alexander, and ZALTRON, Paolo

Subjects
Astrophysics::Instrumentation and Methods for Astrophysics, MATERIALS, AEROSPACE SYSTEMS
Abstract

Traditional cryogenic vibration isolators require elements in contact to isolate the suspended mass. Potential creep, plasticity or permanent elongation issues limit the number of times that these systems can be rebooted thermally. In addition, conducted heat coming from ground compromises the performance of suspended optic and electronic devices. To provide passive vibration isolation and to eliminate heat conducted between the external interface and the suspended mass, a Superconducting Magnetic Suspension (SMS) has been developed by a consortium led by MAG SOAR. The lack of contact makes conduction of heat to be zero. An additional advantage of the SMS is that the energy is dissipated on ground and consequently does not influence the suspended mass. Individual test results have shown that the technology is a promising candidate to future cryogenic space instruments [1]. Based on the lessons learn during the component design, four components have been designed and manufactured at MAG SOAR facilities to support a 12 kg Focal Plane Array (FPA) in cryogenic space-based instruments. An example of a mission utilizing a cryogenic FPA would be the planned X-ray observatory ATHENA. The vibration isolator and thermal disconnect can be scale up and re-design depending of the desired suspended mass.

Published
2019
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8. Design of the charged particle diverter for the ATHENA mission

Author

Ferreira, Ivo, primary, Ayre, Mark, primary, Bavdaz, Marcos, primary, Guainazzi, Matteo, primary, Stefanescu, Alexander, primary, Hynek, R., primary, Sobotka, P., primary, Pejchal, T., primary, Kalousek, R., primary, Bacovsky, J., primary, Zlámal, Jakub, primary, Komárek, Martin, primary, Valenta, Tomas, primary, Závodník, Martin, primary, Badin, V., primary, Horak, M., primary, Flajsman, L., primary, and Wojewoda, O., primary

Published
2018
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11. Design and Application of an Optical High Time Resolution Instrument for High-Energy Transients

Author

Stefanescu, Alexander, Greiner, Jochen (Priv.-Doz. Dr.), Oberauer, Lothar (Prof. Dr.), and Buras, Andrzej Jerzy (Prof. Dr.)

Subjects
Physik, OPTIMA, HTRA, High Time Resolution Astronomy, GRB, Magnetar, Transient, Robotic Observatory, ddc:530
Abstract

Compact astrophysical sources can generate bright outbursts, which show strong variability on short time-scales. Since outbursts of this kind can be readily observed in high-energy detectors, most observations are in the high-energy regime. High time-resolution observations in the optical allow complementary insights into the processes in these outbursts, however the short duration and unpredictable nature of the outbursts so far has precluded successful high time-resolution observations in the optical. In this work I present OPTIMA-Burst, an instrument I have developed for optical high time-resolution observations of high-energy transients. I report of the results of several long-duration observation campaigns, and describe the discovery of an unknown class of transient with extremely fast variability of very large amplitude. Kompakte astrophysikalische Objekte können heftige Strahlungsausbrüche erzeugen, die von starker Variabilität auf kurzen Zeitskalen geprägt sind. Da derartige Ausbrüche mit Hochenergie-Detektoren besonders auffällig sind, werden diese meist zu Ihrer Untersuchung eingesetzt. Zeitlich hochauflösende Beobachtungen im Optischen erlauben komplementäre Einblicke in die Prozesse im Inneren derartiger Ausbrüche, allerdings haben Unvorhersagbarkeit und kurze Dauer für die meisten Arten von Ausbrüchen eine erfolgreiche Beobachtung mit hoher Zeitauflösung im optischen bislang verhindert. In dieser Arbeit stelle ich OPTIMA-Burst vor, ein Instrument welches ich zur zeitlich hochauflösenden Beobachtung von Hochenergie-Transienten im Optischen entwickelt habe. Ich berichte von mehreren Beobachtungskampagnen und der Entdeckung einer unbekannten Klasse von Transient mit außerordentlich starker und schneller optischen Variabilität.

Published
2011

12. Design of the charged particle diverter for the ATHENA mission

Author

den Herder, Jan-Willem A., Nikzad, Shouleh, Nakazawa, Kazuhiro, Ferreira, Ivo, Ayre, Mark, Bavdaz, Marcos, Guainazzi, Matteo, Stefanescu, Alexander, Komárek, M., Valenta, T., Hynek, R., Závodník, M., Sobotka, P., Pejchal, T., Badin, V., Kalousek, R., Bačovský, J., Horák, M., Flajšman, L., Wojewoda, O., and Zlámal, J.

Published
2018
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13. DEPFET Macropixel Detectors for MIXS: Integration and Qualification of the Flight Detectors

Author

Majewski, Petra, primary, Andricek, Ladislav, additional, Bahr, Alexander, additional, De Vita, Giulio, additional, Gunther, Bettina, additional, Hermenau, Kathrin, additional, Hilchenbach, Martin, additional, Lauf, Thomas, additional, Lechner, Peter, additional, Lutz, Gerhard, additional, Miessner, Danilo, additional, Porro, Matteo, additional, Reiffers, Jonas, additional, Richter, Rainer, additional, Schaller, Gerhard, additional, Schnecke, Martina, additional, Schopper, Florian, additional, Soltau, Heike, additional, Stefanescu, Alexander, additional, Strecker, Rafael, additional, Struder, Lothar, additional, and Treis, Johannes, additional

Published
2012
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14. New simulation and measurement results on gateable DEPFET devices

Author

Bähr, Alexander, primary, Aschauer, Stefan, additional, Hermenau, Katrin, additional, Herrmann, Sven, additional, Lechner, Peter H., additional, Lutz, Gerhard, additional, Majewski, Petra, additional, Miessner, Danilo, additional, Porro, Matteo, additional, Richter, Rainer H., additional, Schaller, Gerhard, additional, Sandow, Christian, additional, Schnecke, Martina, additional, Schopper, Florian, additional, Stefanescu, Alexander, additional, Strüder, Lothar, additional, and Treis, Johannes, additional

Published
2012
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15. Integration and calibration of DEPFET macropixel detectors for MIXS

Author

Majewski, Petra, primary, Aschauer, Florian, additional, Bähr, Alexander, additional, de Vita, Giulio, additional, Günther, Bettina, additional, Hermenau, Kathrin, additional, Herrmann, Sven, additional, Hilchenbach, Martin, additional, Lauf, Thomas, additional, Lechner, Peter, additional, Lutz, Gerhard, additional, Miessner, Danilo, additional, Porro, Matteo, additional, Reiffers, Jonas, additional, Schaller, Gerhard, additional, Schopper, Florian, additional, Soltau, Heike, additional, Stefanescu, Alexander, additional, Strecker, Rafael, additional, Strüder, Lothar, additional, and Treis, Johannes, additional

Published
2012
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17. Development and Characterization of New 256$\,\times\,$256 Pixel DEPFET Detectors for X-Ray Astronomy

Author

Meuris, Aline, primary, Aschauer, Florian, additional, De Vita, Giulio, additional, Guenther, Bettina, additional, Herrmann, Sven, additional, Lauf, Thomas, additional, Lechner, Peter, additional, Lutz, Gerhard, additional, Majewski, Petra, additional, Miessner, Danilo, additional, Porro, Matteo, additional, Reiffers, Jonas, additional, Stefanescu, Alexander, additional, Schopper, Florian, additional, Soltau, Heike, additional, Strueder, Lothar, additional, and Treis, Johannes, additional

Published
2011
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18. DEPFET Macropixel Detectors for MIXS: First Electrical Qualification Measurements

Author

Majewski, Petra, primary, Andricek, Ladislav, additional, Christensen, Ulrich, additional, Hilchenbach, Martin, additional, Lauf, Thomas, additional, Lechner, Peter, additional, Lutz, Gerhard, additional, Reiffers, Jonas, additional, Richter, Rainer, additional, Schaller, Gerhard, additional, Schnecke, Martina, additional, Schopper, Florian, additional, Soltau, Heike, additional, Stefanescu, Alexander, additional, Struder, Lothar, additional, and Treis, Johannes, additional

Published
2010
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19. The IXO wide-field imager

Author

Lechner, Peter, primary, Aschauer, Florian, additional, Bombelli, Luca, additional, Fiorini, Carlo, additional, Herrmann, Sven, additional, Lauf, Thomas, additional, Lutz, Gerhard, additional, Majewski, Petra, additional, Meuris, Aline, additional, Porro, Matteo, additional, Reiffers, Jonas, additional, Richter, Rainer, additional, Stefanescu, Alexander, additional, Strüder, Lothar, additional, Treis, Johannes, additional, and De Vita, Giulio, additional

Published
2010
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20. First results from electrical qualification measurements on DEPFET pixel detector

Author

Majewski, Petra, primary, Andricek, Ladislav, additional, Lauf, Thomas, additional, Lechner, Peter, additional, Lutz, Gerhard, additional, Reiffers, Jonas, additional, Richter, Rainer, additional, Schaller, Gerhard, additional, Schnecke, Martina, additional, Schopper, Florian, additional, Soltau, Heike, additional, Stefanescu, Alexander, additional, Strüder, Lothar, additional, and Treis, Johannes, additional

Published
2010
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21. The wide-field imager for IXO: status and future activities

Author

Strüder, Lothar, primary, Aschauer, Florian, additional, Bautz, Mark, additional, Bombelli, Luca, additional, Burrows, David, additional, Fiorini, Carlo, additional, Fraser, George, additional, Herrmann, Sven, additional, Kendziorra, Eckhard, additional, Kuster, Markus, additional, Lauf, Thomas, additional, Lechner, Peter, additional, Lutz, Gerhard, additional, Majewski, Petra, additional, Meuris, Aline, additional, Porro, Matteo, additional, Reiffers, Jonas, additional, Richter, Rainer, additional, Santangelo, Andrea, additional, Soltau, Heike, additional, Stefanescu, Alexander, additional, Tenzer, Chris, additional, Treis, Johannes, additional, Tsunemi, Hiroshi, additional, de Vita, Giulio, additional, and Wilms, Jörn, additional

Published
2010
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23. Optical test results of fast pnCCDs

Author

Ihle, Sebastian, primary, Hartmann, Robert, additional, Downing, Marc, additional, Struder, Lothar, additional, Deiries, Sebastian, additional, Gorke, Hubert, additional, Hermann, Sven, additional, Kanbach, Gottfried, additional, Papamasturakis, Janis, additional, Soltau, Heike, additional, and Stefanescu, Alexander, additional

Published
2008
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24. Results of a pnCCD detector system for high-speed optical imaging

Author

Hartmann, Robert, primary, Deires, Sebastian, additional, Downing, Mark, additional, Gorke, Hubert, additional, Herrmann, Sven, additional, Ihle, Sebastian, additional, Kanbach, Gottfried, additional, Papamastorakis, Janis, additional, Soltau, Heike, additional, Stefanescu, Alexander, additional, and Strüder, Lothar, additional

Published
2008
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27. pnCCDs for Ultra-Fast and Ultra-Sensitive Optical and NIR Imaging

Author

Holl, Peter, primary, Hartmann, Robert, additional, Ihle, Sebastian, additional, Kanbach, Gottfried, additional, Lutz, Gerhard, additional, Ordavo, Ivan, additional, Soltau, Heike, additional, Stefanescu, Alexander, additional, Strüder, Lothar, additional, Phelan, Don, additional, Ryan, Oliver, additional, and Shearer, Andrew, additional

Published
2008
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