Details

Autor(en) / Beteiligte

• Nones, C.
• Marnieros, S.
• Benoit, A.
• Bergé, L.
• Bideaud, A.
• Camus, P.
• Dumoulin, L.
• Monfardini, A.
• Rigaut, O.

Titel

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

Ist Teil von

• Astronomy and astrophysics (Berlin), 2012-12, Vol.548, p.A17

Ort / Verlag

EDP Sciences

Erscheinungsjahr

2012

Quelle

EZB Electronic Journals Library

Beschreibungen/Notizen

• 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 7×10-16 W/\hbox{$\!\sqrt{\rm Hz}$}Hz, which is highly encouraging given the scope for improvement in this type of detectors.