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Bolometric astronomical imaging at mm wavelengths

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Presentation on theme: "Bolometric astronomical imaging at mm wavelengths"— Presentation transcript:

1 Bolometric astronomical imaging at mm wavelengths
Stephen Yates CNRS-CRTBT Grenoble - Astrophysique et matière noire groupe: Alain Benoit, Philippe Camus, François-Xavier Désert and Samuel Leclercq. Talk to European network on cryodetectors, 23/4/2004 1CNRS, Centre de Recherche sur les Très Basses Températures, CEDEX 9, Grenoble, France

2 Bolometers projects at the CRTBT
Ground based bolometric camera observation at mm wavelengths Archeops: balloon based mm observation (2001/2) Planck: satellite space observation of cosmic microwave background (projected 2007) Edelweiss II, dark matter detection

3 Bolometric camera Current systems: Our goal: Ground based imaging
mainly 300mK, 100s of individual bolometers (e.g. MAMBO, lower figure) Our goal: Bolometric Integrated bolometer array of up to 1000 pixels

4 Bolometer electronic Readout
Capacitive current source Low temperature JFET Low noise measurements Modulated square wave excitation Reduces sensitivity to offset drift reduces amplifier 1/f and shifts to modulation frequency. Enables measurement of up to 30MW Automated data acquisition and control Triangle, generates square wave current through capacitor Low temperature JFET, enables amplifier noise~0.5nV/Hz1/2 bolometer Square wave reference

5 Multiplexing bolometer readout
For 1000 pixels, necessary to multiplex detectors to reduce electronics/complexity Low temperature operation Successfully built and tested a multiplexer to read 8 bolometers Testing HEMT Quantum Point Contact transistor network (shown), made by Y.Jin (IPN) Lower capacitance/dissipation I Transistor switches Vmeas Vref Quantum behaviour of QPC transistor

6 Microfabricated bolometer arrays
Thin film bolometers, based on a thin membrane, built and tested Characterisation using a low temperature black body source NbxSi1-x thermometer layer, fabricated at CSNSM Paris (L. Dumoulin) Bolometer, 5x5mm, 100nm membrane Black body source and optics

7 Bolometer arrays Array of 4 bolometers on chip
Tested thermal conductivity of membrane and resistivity of thermometer.

8 Further work Expanding bolometer arrays,
optimising fabrication of individual bolometers Antenna for bolometers (array shown) Fourier spectrometer Expanding/testing multiplexing Optics for camera, filters for low temperature operation, refrigerator


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