Dr. Alex Zehnder Profile

Dr. Alex Zehnder

at Paul Scherrer Institut

SPIE Involvement:

Author

Publications (21)

Proceedings Article | 25 July 2008 Paper

Paper

Cryogenic wheel mechanisms for the Mid-Infrared Instrument (MIRI) of the James Webb Space Telescope (JWST): detailed design and test results from the qualification program

O. Krause, S. Birkmann, T. Blümchen, A. Böhm, M. Ebert, U. Grözinger, Th. Henning, R. Hofferbert, A. Huber, D. Lemke, R.-R. Rohloff, S. Scheithauer, T. Gross, G. Luichtel, C. Stein, R. Stott, M. Übele, J. Amiaux, J.-L. Auguères, A. Glauser, A. Zehnder, M. Meijers, R. Jager, P. Parr-Burrman, G. Wright

Proceedings Volume 7018, 701824 (2008) https://doi.org/10.1117/12.789319

KEYWORDS: Interfaces, James Webb Space Telescope, Kinematics, Cryogenics, Position sensors, Sensors, Mid-IR, Magnetism, Spectroscopy, Optical filters

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Proceedings Article | 23 July 2008 Paper

Paper

A contamination control cover for the Mid Infrared Instrument of the James Webb Space Telescope

Adrian Glauser, Ulrich Langer, Alex Zehnder, Manuel Güdel

Proceedings Volume 7018, 70184L (2008) https://doi.org/10.1117/12.789467

KEYWORDS: Current controlled current source, James Webb Space Telescope, Actuators, Contamination control, Mid-IR, Coronagraphy, Temperature metrology, Shape memory alloys, Fermium, Frequency modulation

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Proceedings Article | 12 July 2008 Paper

Paper

Design and development of MIRI, the mid-IR instrument for JWST

G. Wright, G. Reike, P. Barella, T. Boeker, L. Colina, E. van Dishoeck, P. Driggers, G. Goodson, T. Greene, A. Heske, T. Henning, P.-O. Lagage, M. Meixner, H. Norgaard-Nielsen, G. Olofsson, T. Ray, M. Ressler, J. Thatcher, C. Waelkens, D. Wright, A. Zehnder

Proceedings Volume 7010, 70100T (2008) https://doi.org/10.1117/12.790101

KEYWORDS: James Webb Space Telescope, Spectroscopy, Imaging systems, Sensors, Coronagraphy, Calibration, Mid-IR, Instrument modeling, Data modeling, Observatories

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Proceedings Article | 18 July 2006 Paper

Paper

Wide field compact detector for hard x-ray polarization measurements

W. Hajdas, N. Produit, E. Suarez-Garcia, F. Barao, C. Casella, K. Deiters, S. Deluit, C. Leluc, A. Mchedlishvilli, M. Pohl, D. Rapin, Ch. Tao, J.-P. Vialle, R. Walter, C. Wigger, A. Zehnder

Proceedings Volume 6266, 62662W (2006) https://doi.org/10.1117/12.672067

KEYWORDS: Sensors, Polarization, Scintillators, Modulation, Gamma radiation, Polarimetry, Photon polarization, Compton scattering, X-rays, Monte Carlo methods

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Proceedings Article | 12 October 2004 Paper

Paper

The JWST MIRI instrument concept

Gillian Wright, George Rieke, Luis Colina, Ewine van Dishoeck, Greg Goodson, Tom Greene, Pierre-Olivier Lagage, Avinash Karnik, Scott Lambros, Dietrich Lemke, Margaret Meixner, Hans-Ulrich Norgaard, Goran Oloffson, Tom Ray, Michael Ressler, Christoffel Waelkens, David Wright, Alex Zhender

Proceedings Volume 5487, (2004) https://doi.org/10.1117/12.551717

KEYWORDS: Sensors, Spectroscopy, James Webb Space Telescope, Imaging systems, Imaging spectroscopy, Electronics, Thermography, Mirrors, Signal detection, Cryogenics

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Proceedings Article | 29 September 2004 Paper

Paper

Positioning of optical elements in the cryogenically cooled mid-infrared instrument MIRI for the James Webb Space Telescope

Dietrich Lemke, Ralph Hofferbert, Ulrich Grozinger, Ralf-Rainer Rohloff, Armin Bohm, Thomas Henning, Armin Huber, Stefan Mertin, Jose Ramos, Gillian Wright, Peter Hastings, Alex Zehnder, Sophie Salasca, Gabby Kroes, Christian Straubmeier, Andreas Eckart

Proceedings Volume 5495, (2004) https://doi.org/10.1117/12.550398

KEYWORDS: James Webb Space Telescope, Spectroscopy, Mirrors, Sensors, Electronics, Imaging systems, Optical components, Mid-IR, Optical filters, Picture Archiving and Communication System

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Proceedings Article | 4 February 2004 Paper

Paper

The Reuven Ramaty High-Energy Solar Spectroscopic Imager (RHESSI) mission

Robert Lin, Brian Dennis, Gordon Hurford, David Smith, Alex Zehnder

Proceedings Volume 5171, (2004) https://doi.org/10.1117/12.506649

KEYWORDS: Electrons, Solar energy, Gamma radiation, Imaging spectroscopy, Hard x-rays, Solar processes, X-rays, Ions, Sun, Curium

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Proceedings Article | 11 March 2003 Paper

Paper

Nonsolar astronomy with the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI)

David Smith, Robert Lin, Kevin Hurley, Wayne Coburn, Gordon Hurford, Claudia Wigger, W. Hajdas, Alex Zehnder, Mark McConnell

Proceedings Volume 4851, (2003) https://doi.org/10.1117/12.461415

KEYWORDS: Sensors, Solar energy, Photons, Imaging systems, Gamma radiation, Spectroscopy, Space operations, Modulation, Imaging spectroscopy, Magnetism

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Proceedings Article | 11 February 2003 Paper

Paper

RHESSI imager and aspect systems

Alex Zehnder, Jacek Bialkowski, F. Burri, Martin Fivian, Reinhold Henneck, A. Mchedlishvili, P. Ming, J. Welte, Knud Thomsen, David Clark, Brian Dennis, Gordon Hurford, David Curtis, Peter Harvey, David Pankow

Proceedings Volume 4853, (2003) https://doi.org/10.1117/12.460290

KEYWORDS: Charge-coupled devices, Imaging systems, Stars, Space operations, Sun, Electronics, Interference (communication), CCD image sensors, Lenses, Sensors

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Proceedings Article | 11 February 2003 Paper

Paper

RHESSI aspect system and in-flight calibration

Martin Fivian, Reinhold Henneck, Alex Zehnder

Proceedings Volume 4853, (2003) https://doi.org/10.1117/12.460365

KEYWORDS: Charge-coupled devices, Stars, Calibration, Sun, Imaging systems, Sensors, Space operations, Interference (communication), Telescopes, Space telescopes

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Proceedings Article | 13 December 2000 Paper

Paper

In-flight calibration of the XMM-Newton reflection grating spectrometers

Christian Erd, M. Audard, Antonius den Boggende, Graziella Branduardi-Raymont, A. Brinkman, Jean Cottam, Luc Dubbeldam, Manuel Guedel, Jan-Willem den Herder, Jelle Kaastra, Steven Kahn, Rolf Mewe, Frits Paerels, John Peterson, Andrew Rasmussen, Irini Sakelliou, Joshua Spodek, Knud Thomsen, Cor de Vries, Alex Zehnder

Proceedings Volume 4140, (2000) https://doi.org/10.1117/12.409112

KEYWORDS: Calibration, Charge-coupled devices, Roentgenium, Dispersion, Cameras, Spectrometers, Diffraction gratings, Spectral resolution, Mirrors, Diffraction

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Proceedings Article | 18 July 2000 Paper

Paper

Calibrating the aspect systems of the high-energy solar spectroscopic imager (HESSI)

Martin Fivian, Jacek Bialkowski, W. Hajdas, Reinhold Henneck, A. Mchedlishvili, P. Ming, Knud Thomsen, Alex Zehnder, Gordon Hurford, David Curtis, David Pankow, Brian Dennis

Proceedings Volume 4012, (2000) https://doi.org/10.1117/12.391587

KEYWORDS: Charge-coupled devices, Stars, Sun, Imaging systems, Calibration, Solar energy, Space operations, CCD image sensors, Spatial resolution, Imaging spectroscopy

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Proceedings Article | 18 July 2000 Paper

Paper

Calibrating the imaging system of the high-energy solar spectroscopic imager (HESSI)

Knud Thomsen, Jacek Bialkowski, F. Burri, Martin Fivian, W. Hajdas, A. Mchedlishvili, P. Ming, J. Welte, Alex Zehnder

Proceedings Volume 4012, (2000) https://doi.org/10.1117/12.391588

KEYWORDS: Imaging systems, Imaging spectroscopy, Calibration, Solar energy, Solar processes, Modulation, Space operations, Spectroscopy, Spatial resolution, Hard x-rays

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Proceedings Article | 22 October 1999 Paper

Paper

Solar Aspect System (SAS) for the High-Energy Solar Spectroscopic Imager (HESSI)

Reinhold Henneck, Jacek Bialkowski, F. Burri, Martin Fivian, W. Hajdas, A. Mchedlishvili, P. Ming, Knud Thomsen, J. Welte, Alex Zehnder, Brian Dennis, Gordon Hurford, David Curtis, David Pankow

Proceedings Volume 3765, (1999) https://doi.org/10.1117/12.366560

KEYWORDS: Charge-coupled devices, Sun, Imaging systems, Space operations, Solar energy, Fermium, Frequency modulation, Data processing, Light emitting diodes, Imaging spectroscopy

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Proceedings Article | 22 October 1999 Paper

Paper

Roll Angle System (RAS) for the High-Energy Solar Spectroscopic Imager HESSI

Reinhold Henneck, Jacek Bialkowski, F. Burri, Martin Fivian, W. Hajdas, A. Mchedlishvili, P. Ming, Knud Thomsen, J. Welte, Alex Zehnder, M. Dettwyler, F. Buerki, Gordon Hurford, David Curtis, David Pankow

Proceedings Volume 3765, (1999) https://doi.org/10.1117/12.366530

KEYWORDS: Stars, Charge-coupled devices, Sun, Imaging systems, Satellites, Reflectivity, Imaging spectroscopy, Spectroscopy, Space operations, Scanners

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Proceedings Article | 2 November 1998 Paper

Paper

High-Energy Solar Spectroscopic Imager (HESSI) Small Explorer mission for the next (2000) solar maximum

Robert Lin, Gordon Hurford, Norman Madden, Brian Dennis, Carol Crannell, Gordon Holman, Reuven Ramaty, Tycho von Rosenvinge, Alex Zehnder, H. Frank van Beek, Patricia Bornmann, Richard Canfield, A. Gordon Emslie, Hugh Hudson, Arnold Benz, John Brown, Shinzo Enome, Takeo Kosugi, Nicole Vilmer, David Smith, Jim McTiernan, Isabel Hawkins, Said Slassi-Sennou, Andre Csillaghy, George Fisher, Chris Johns-Krull, Richard Schwartz, Larry Orwig, Dominic Zarro, Ed Schmahl, Markus Aschwanden, Peter Harvey, David Curtis, David Pankow, David Clark, Robert Boyle, Reinhold Henneck, Akilo Michedlishvili, Knud Thomsen, Jeff Preble, Frank Snow

Proceedings Volume 3442, (1998) https://doi.org/10.1117/12.330245

KEYWORDS: Electrons, Imaging spectroscopy, Solar energy, X-rays, Spatial resolution, Space operations, Sensors, Hard x-rays, Ions, Sun

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Proceedings Article | 31 October 1996 Paper

Paper

Reflection Grating Spectrometer on board XMM

A. Brinkman, Henry Aarts, Antonius den Boggende, T. Bootsma, Luc Dubbeldam, Jan-Willem den Herder, Jelle Kaastra, Piet de Korte, Boris van Leeuwen, Rolf Mewe, E. van Zwet, Todd Decker, Charles Hailey, Steven Kahn, Frits Paerels, Steven Pratuch, Andrew Rasmussen, Graziella Branduardi-Raymont, Phil Guttridge, Jay Bixler, Knud Thomsen, Alex Zehnder, Christian Erd

Proceedings Volume 2808, (1996) https://doi.org/10.1117/12.256019

KEYWORDS: Charge-coupled devices, Roentgenium, Sensors, X-rays, Diffraction gratings, Telescopes, Calibration, Spectroscopy, Spectral resolution, CCD cameras

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Proceedings Article | 18 October 1996 Paper

Paper

Imager onboard INTEGRAL

Pietro Ubertini, Guido Di Cocco, Francois Lebrun, L. Bassani, Angela Bazzano, Antony Bird, Kjell Broenstad, Ezio Caroli, M. Denis, Andrea Goldwurm, Claudio Labanti, Phillipe Laurent, Giuseppe Malaguti, I. Mirabel, Lorenzo Natalucci, M. Quadrini, Brian Ramsey, Victor Reglero, L. Sabau, Bruno Sacco, Ruediger Staubert, Laurent Vigroux, Martin Weisskopf, A. Zdziarski, Alex Zehnder

Proceedings Volume 2806, (1996) https://doi.org/10.1117/12.253984

KEYWORDS: Imaging systems, Sensors, X-rays, Spatial resolution, Calibration, Image resolution, Stars, Gamma radiation, Galactic astronomy, Tungsten

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Proceedings Article | 13 September 1994 Paper

Paper

Reflection grating spectrometer onboard the ESA x-ray multi-mirror (XMM) mission

Jan-Willem den Herder, Henry Aarts, Marcel van den Berg, Jay Bixler, Antonius den Boggende, Graziella Branduardi-Raymont, A. Brinkman, Todd Decker, Luc Dubbeldam, Charles Hailey, Fred Jansen, Steven Kahn, Piet de Korte, C. Mauche, Richard Montesanti, Frits Paerels, Hugo Spruijt, Knud Thomsen, Peter Verhoeve, Alex Zehnder

Proceedings Volume 2209, (1994) https://doi.org/10.1117/12.185279

KEYWORDS: Mirrors, Charge-coupled devices, X-rays, Roentgenium, Cameras, X-ray telescopes, Back illuminated sensors, CCD cameras, Spectral resolution, Telescopes

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The Reflection Grating Spectrometer (RGS) onboard the ESA satellite XMM (X-ray Multi Mirror mission) combines a high resolving power (approximately 400 at 0.5 keV) with a large effective area (approximately 200 cm²). The spectral range selected for RGS (5 - 35 angstroms) contains the K shell transitions of N, O, Ne, Mg, Al, Si and S as well as the important L shell transitions of FE. The resolving power allows the study of a wide variety of challenging scientific questions. Detailed temperature diagnostics are feasible as the ionization balance is a unique function of the distribution of the electron temperature. Density diagnostics are provided by studying He-like triplets where the ratio of the forbidden to intercombination lines varies with density. Other fields of interest include the determination of elemental abundances, the study of optical depth effects, velocity diagnostics by measuring Doppler shifts and the estimate of magnetic fields through the observation of Zeeman splitting. The resolving power is obtained by an array of 240 gratings placed behind the mirrors of the telescope, dispersing about half of the X-rays in two spectroscopic orders. The X-rays are recorded by an array of 9 large format CCDs. These CCDs are operated in the frame transfer mode. They are back illuminated as the quantum efficiency of front illuminated devices is poor at low energies because of their poly-silicon gate structure. To suppress dark current the CCDs are passively cooled. In order to obtain the effective area of about 200 cm², grating arrays and CCD cameras are placed behind two of the three XMM telescopes. A model of RGS was tested last autumn ('93) at the Panter long beam X-ray facility in Munich. The model consisted of a subset of four mirrors, eight representative gratings covering a small section of the inner mirror shells and a CCD camera containing three CCDs. The purpose of these tests was to verify the resolution and sensitivity of the instrument as a function of X-ray energy. Extensive simulations, using a Monte Carlo raytracing code, are used to interpret these tests. Preliminary results of these tests will be discussed and compared to the calculated response.

Proceedings Article | 1 November 1990 Paper

Paper

Superconducting tunneling junction detectors

Alex Zehnder, C. Hagen, W. Rothmund

Proceedings Volume 1344, (1990) https://doi.org/10.1117/12.23256

KEYWORDS: Quasiparticles, Sensors, Superconductors, Phonons, X-rays, Tin, X-ray astronomy, Lead, Absorption, Extreme ultraviolet

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Proceedings Article | 1 November 1990 Paper

Paper

Extreme UV imaging telescope array on the spectrum X-G satellite

Alex Zehnder, Joerg Bialkowski, P. Buehler, E. Morenzoni, Nick Schlumpf, W. Schoeps, Knud Thomsen, T. Courvoisier, A. Orr, L. Chesalin, V. Dremin, D. Stepanov, Rashid Sunyaev, Oswald Siegmund, John Vallerga, Peter Vedder, Supriya Chakrabarti, John Warren, Giovanni Bonanno, Gordon Walker, K. Lund

Proceedings Volume 1344, (1990) https://doi.org/10.1117/12.23246

KEYWORDS: Sensors, Extreme ultraviolet, Telescopes, Space telescopes, X-rays, X-ray astronomy, Stars, Mirrors, Microchannel plates, Gamma radiation

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Showing 5 of 21 publications

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