Share Email Print
cover

Journal of Astronomical Telescopes, Instruments, and Systems • Open Access • new

Complex spectral line profiles resulting from cryogenic deformation of the SINFONI/SPIFFI diffraction gratings
Author(s): Elizabeth M. George; Dominik Gräff; Michael Hartl; Heinrich Huber; Frank Eisenhauer; Helmut Feuchtgruber

Paper Abstract

The integral field spectrograph, spectrometer for infrared faint field imaging (SPIFFI), has complex line profile shapes that vary with wavelength and pixel scale, the origins of which have been sought since the instrument construction. SPIFFI is currently operational as part of SINFONI at the Very Large Telescope (VLT) and will be upgraded and incorporated into the VLT instrument enhanced resolution imager and spectrograph (ERIS). We conducted an investigation of the line profiles based on the measurements we could take with the instrument calibration unit, as well as laboratory measurements of spare SPIFFI optical components. Cryogenic measurements of a spare SPIFFI diffraction grating showed significant periodic deformation. These measurements match the cryogenic deformation expected from bimetallic bending stress based on a finite element analysis of the lightweighted grating blank. The periodic deformation of the grating surface gives rise to satellite peaks in the diffraction pattern of the grating. An optical simulation including the cryogenic grating deformation reproduces the behavior of the SPIFFI line profiles with both wavelength and pixel scale as measured with the instrument calibration unit. The conclusion is that cryogenic deformation of the diffraction gratings is responsible for the nonideal line profiles, and that the diffraction gratings should be replaced during the upgrade for optimal instrument performance.

Paper Details

Date Published: 27 July 2017
PDF: 16 pages
J. Ast. Inst. Sys. 3(3) 035002 doi: 10.1117/1.JATIS.3.3.035002
Published in: Journal of Astronomical Telescopes, Instruments, and Systems Volume 3, Issue 3
Show Author Affiliations
Elizabeth M. George, Max Planck Institut für Extraterrestrische Physik (Germany)
European Southern Observatory (Germany)
Dominik Gräff, Max Planck Institut für Extraterrestrische Physik (Germany)
ETH Zürich Laboratory of Hydraulics, Hydrology and Glaciology (Switzerland)
Michael Hartl, Max Planck Institut für Extraterrestrische Physik (Germany)
Heinrich Huber, Max Planck Institut für Extraterrestrische Physik (Germany)
Frank Eisenhauer, Max Planck Institut für Extraterrestrische Physik (Germany)
Helmut Feuchtgruber, Max Planck Institut für Extraterrestrische Physik (Germany)


© SPIE. Terms of Use
Back to Top