15 October 2003 Design and performances of a cryogenic Fabry-Perot for submillimeter astronomy
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Abstract
We present the Fabry-Perot designed for FIBRE and its evolution for its use in the SAFIRE imaging spectrometer for the SOFIA airborne telescope. The Fabry-Perot Interferometer Bolometer Research Experiment (FIBRE) is a broadband submillimeter spectrometer for the Caltech Submillimeter Observatory (CSO). FIBRE's detectors are superconducting transition edge sensor (TES) bolometers read out by SQUID multiplexers. During the first light of FIBRE in June 2001, we measured a spectral resolution of about 1200. The Fabry-Perot concept has its heritage in the ISO/LWS instrument, scaled and adapted to the submillimeter range. The semi-reflecting optics consist of a metallic meshe deposited on a lens and a wedged plate made of monocrystalline quartz. We use three voice coil actuators in the Fabry-Perot design to achieve a displacement of 600 microns of the moving plate. The use of NbTi superconducting wire for the coils allows operation at 1.5 K without any Joule dissipation. Capacitive sensors in line with each actuator and their AC readout provide three independant position measurements. These measurements are fed into a triple PID amplifier controlling the actuators. Because of the high level of vibrations present on an airborne instrument platform, it it necessary to reject the vibrations in the Fabry-Perot up to the resonance frequencies. We propose an original method to obtain a frequency response of the PID system up to 60 Hz. The updated Fabry-Perot will be used for the next FIBRE run in autumn 2003, aiming to detect the Doppler-broadened line emission from external galaxies.
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Francois P. Pajot, Francois P. Pajot, Bruno Maffei, Bruno Maffei, Dominic J. Benford, Dominic J. Benford, Dale J. Fixsen, Dale J. Fixsen, Sebastien Lefranc, Sebastien Lefranc, S. Harvey Moseley, S. Harvey Moseley, Cyrille Rioux, Cyrille Rioux, Rick A. Shafer, Rick A. Shafer, Gaurav J. Shah, Gaurav J. Shah, Johannes G. Staguhn, Johannes G. Staguhn, } "Design and performances of a cryogenic Fabry-Perot for submillimeter astronomy", Proc. SPIE 5172, Cryogenic Optical Systems and Instruments X, (15 October 2003); doi: 10.1117/12.506858; https://doi.org/10.1117/12.506858
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