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High-impedance NbSi TES sensors for studying the cosmic microwave background radiation

C. Nones 1 S. Marnieros 1 Alain Benoit 2 L. Berge 3 A. Bideaud 2 P. Camus 4 L. Dumoulin 1 Alessandro Monfardini 2 O. Rigaut 1
CSNSM - Centre de Spectrométrie Nucléaire et de Spectrométrie de Masse, CSNSM - Centre de Sciences Nucléaires et de Sciences de la Matière
CSNSM - Centre de Spectrométrie Nucléaire et de Spectrométrie de Masse
Abstract : Precise measurements of the cosmic microwave background (CMB) are crucial in cosmology because any proposed model of the universe must account for the features of this radiation. The CMB has a thermal blackbody spectrum at a temperature of 2.725 K, i.e. the spectrum peaks in the microwave range frequency of 160.2 GHz, corresponding to a 1.9-mm wavelength. Of all CMB measurements that the scientific community has not yet been able to perform, the CMB B-mode polarization is probably the most challenging from the instrumental point of view. The signature of primordial gravitational waves, which give rise to a B-type polarization, is one of the goals in cosmology today and amongst the first objectives in the field. For this purpose, high-performance low-temperature bolometric cameras, made of thousands of pixels, are currently being developed by many groups, which will improve the sensitivity to B-mode CMB polarization by one or two orders of magnitude compared to the Planck satellite HFI detectors. We present here a new bolometer structure that is able to increase the pixel sensitivities and to simplify the fabrication procedure. This innovative device replaces delicate membrane-based structures and eliminates the mediation of phonons: the incoming energy is directly captured and measured in the electron bath of an appropriate sensor and the thermal decoupling is achieved via the intrinsic electron-phonon decoupling of the sensor at very low temperature. Reported results come from a 204-pixel array of NbxSi1-x transition edge sensors with a meander structure fabricated on a 2-inch silicon wafer using electron-beam co-evaporation and a cleanroom lithography process. To validate the application of this device to CMB measurements, we have performed an optical calibration of our sample in the focal plane of a dilution cryostat test bench. We have demonstrated a light absorption close to 20% and an optical noise equivalent power of about 7 x 10(-16) W/root Hz, which is highly encouraging given the scope for improvement in this type of detectors.
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Submitted on : Monday, January 14, 2013 - 11:57:50 AM
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C. Nones, S. Marnieros, Alain Benoit, L. Berge, A. Bideaud, et al.. High-impedance NbSi TES sensors for studying the cosmic microwave background radiation. Astronomy and Astrophysics - A&A, EDP Sciences, 2012, 548, pp.A17. ⟨10.1051/0004-6361/201218834⟩. ⟨in2p3-00773565⟩



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