bolometric astronomical imaging at mm wavelengths stephen yates cnrs-crtbt grenoble - astrophysique...

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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 1 CNRS, Centre de Recherche sur les Très Basses Températures, 38042 CEDEX 9, Grenoble, France

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Page 1: Bolometric astronomical imaging at mm wavelengths Stephen Yates CNRS-CRTBT Grenoble - Astrophysique et matière noire groupe: Alain Benoit, Philippe Camus,

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, 38042 CEDEX 9, Grenoble, France

Page 2: Bolometric astronomical imaging at mm wavelengths Stephen Yates CNRS-CRTBT Grenoble - Astrophysique et matière noire groupe: Alain Benoit, Philippe Camus,

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

Page 3: Bolometric astronomical imaging at mm wavelengths Stephen Yates CNRS-CRTBT Grenoble - Astrophysique et matière noire groupe: Alain Benoit, Philippe Camus,

Bolometric camera

• Ground based imaging

Current systems:• mainly 300mK, 100s of

individual bolometers (e.g. MAMBO, lower figure)

Our goal:• Bolometric camera @100mK

• Integrated bolometer array of up to 1000 pixels

Page 4: Bolometric astronomical imaging at mm wavelengths Stephen Yates CNRS-CRTBT Grenoble - Astrophysique et matière noire groupe: Alain Benoit, Philippe Camus,

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 30M

• Automated data acquisition and control

Triangle, generates square wave current through capacitor

Square wave reference

bolometer

Low temperature JFET, enables amplifier noise~0.5nV/Hz1/2

Page 5: Bolometric astronomical imaging at mm wavelengths Stephen Yates CNRS-CRTBT Grenoble - Astrophysique et matière noire groupe: Alain Benoit, Philippe Camus,

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

Vref

I

Vmeas

Transistor switches

Quantum behaviour of QPC transistor

Page 6: Bolometric astronomical imaging at mm wavelengths Stephen Yates CNRS-CRTBT Grenoble - Astrophysique et matière noire groupe: Alain Benoit, Philippe Camus,

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)

Black body source and optics

Bolometer, 5x5mm, 100nm membrane

Page 7: Bolometric astronomical imaging at mm wavelengths Stephen Yates CNRS-CRTBT Grenoble - Astrophysique et matière noire groupe: Alain Benoit, Philippe Camus,

Bolometer arrays

• Array of 4 bolometers on chip

• Tested thermal conductivity of membrane and resistivity of thermometer.

Page 8: Bolometric astronomical imaging at mm wavelengths Stephen Yates CNRS-CRTBT Grenoble - Astrophysique et matière noire groupe: Alain Benoit, Philippe Camus,

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