TES Bolometer Array with SQUID readout for Apex

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TES Bolometer Array with SQUID readout for Apex

• V. Zakosarenko, T. May, R. Stolz, H.-G. Meyer,
  Institute for Physical High Technology, Jena
• E. Kreysa, W. Esch, Max Planck Institute for
  Radioastronomy, Bonn

The work is supported by the German BMBF under
the contract No. 05 AA2PC1/3.
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Laboca
Project purpose Large Bolometer Camera (Laboca)
with 300 pixel for sub-millimeter range for
Atacama Pathfinder Experiment (APEX) on array of
12m-telescopes in Chili , Atacama
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Bolometer Principles
Infrared power ?Peiwt ? dT ? dR ? dI
Thermistor transition edge sensor (TES)
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Electro Thermal Feedback
Transition edge sensor with voltage bias
Resistance
Working point
Rw
Temperature
T0
Tc
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Signal Response
Current response
Sharpness of the transition
Effective time constant
Open loop gain
Lgtgt1 wt ltlt 1
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TES Bilayer
Au-Pd (8 nm)
Proximity bilayer with TC 0.5K
Mo (60 nm)
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7-pixel Array
Si N membrane 1µm thick with Ti absorber film on
the back side
Si wafer
Au ring
Thermistor (TES)
7-pixel array chip mounted in the Cu holder plate
(1,5 cm x 1,5 cm)
Nb wiring
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SQUID current sensors
SQUID current sensor chip
µ-metal shield
SQUID holder with 4 mounted current sensors
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Measuring System
SQUID holder with 4 current sensors. The µ-metal
shield is not installed.
Superconducting bolometer chamber (Al)
with7-pixel horn array
3He stage with sorption pump (300mK)
1.5K pot of 4He cryostat
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First Light
30m - radiotelescope of IRAM on Pico Veleta in
Spain, Sierra Nevada.
Cryostat with TES bolometers in telescope cabin
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First Results
The whole system worked stable in the cabin.
But bad weather (snow) ?
Power calculated as IBIAS x RBIAS x Si
Response of the bolometers on the change of black
body temperature (77K ? 300K)
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Next Step
LABOCA Large Bolometer Camera 300 pixel on 4
inch wafer
Laboca should be ready in the middle of the year
2005!
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Multiplexing

• Two possibility
• parallel readout
• ? 300 current sensors each in separate
  packaging, 1250 wires to room temperature
  electronics, 300 FLL electronics.
• ? low risk (familiar way)
• ? mechanical complexity, thermal last, too
  expensive !
• b) multiplexing
• ? 300 SQUID integrated on the wafer with
  bolometers, 30 SQUID amplifier in separate
  packaging, 200 wires to room temperature, 30 FLL
  electronics, and digital controller .
• ? less expensive
• ? new development (challenge !)

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Time Domain MUX
TES bias
Digital control bias switches
Bias
Sinch
Amplifier SQUID
Active SQUID
RESET
FLL electronics,
Out
300K
0.3K
Feedback
1.5K
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Test of the MUX Electronics
Sampling frequency 5 kHz
Sampling frequency 100 kHz
6 separate SQUIDs, SQUID-array as amplifier,
the simplest FLL with two operational amplifiers
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Integrated Bolometer
First samples are fabricated. Tests in the
laboratory will be performed in the next weeks.
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Conclusions

• 7 pixel TES bolometer array with SQUID readout
  shows stable operation in real environment in
  telescope cabin.
• 7 pixel TES bolometer array with integrated
  SQUID is ready for test.
• Time domain multiplexing operates. Optimization
  of bandwidth and noise figure is in progress.
• Great challenge to perform the proposed schedule.