FrequencyDomain Readout Multiplexing of TransitionEdge Sensor Arrays

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Frequency-Domain Readout Multiplexing of
Transition-Edge Sensor Arrays
Trevor Lanting U.C. Berkeley Oct. 5, 2004 ASC
Jacksonville, FL
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Collaboration
UC Berkeley H.-M. Cho J. Clarke W. Holzapfel M.
Lueker A.T. Lee P.L. Richards NIST K. Irwin G.
Hilton M. Huber
Lawrence Berkeley National Lab M.A. Dobbs H.G.
Spieler Northrup Grumman A. Smith
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Outline

• Motivation for Multiplexed Readout
• Frequency-Domain MUX Design
• 8-Channel f-MUX Demonstration, Performance
• Summary

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Motivation for Multiplexed Readout

• Readout for large arrays of detectors (1000 for
  South Pole Telescope)
• Cold multiplexing reduces heat load from wiring,
  reduces readout complexity at low temperatures
• Reduces number of costly cold readout components
  (SQUID arrays, wiring)

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Current Summing f-MUX
300mK
4K
to demodulator

• Current summing MUX
• Row of sensors sinusoidally biased with comb
  of frequencies (0.3 MHz to 1 MHz)
• Only two wires from 300mK stage to read out 8
  channels

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SQUID Electronics
4.2 K

• Slew rate of over 107 F0/s at 1MHz (NIST series
  array SQUID)
• Single-pole roll-off controls stability of
  feedback
• 0.2 m wiring to 4K
• Shunt feedback lowers input impedance

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SQUID Arrays

• Fabricated at NIST
• 100 SQUIDs in series
• Maximum transresistance
• of 500O
• SQUID noise of lt 2 pA/Hz1/2
  referred input coil

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Tuned Filters
20 mm

• Niobium coil on niobium washer
• L 15.8 µH

2 mm

• ceramic NP0
• C 1 nF to 10 nF

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8-Channel f-MUX Readout Noise
T 1.8K
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8-Channel f-MUX Crosstalk
Optical crosstalk between adjacent mm-wave
bolometers 0.01 ( Design requirement
crosstalk lt 0.01 ) Measured adjacent channel
crosstalk lt 0.004
Demodulated Spectra of Channels 2, 3 (84Hz LED
signal)
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8-Channel f-MUX Sensor Noise
Demodulated Spectrum of Channel 2
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Summary

• Frequency domain readout multiplexing of 8
  channels demonstrated
• Crosstalk well below design requirements
• Multiplexed sensors show expected detector
  performance at frequencies down to 200 mHz.

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The Future

• Implement carrier nulling
• 8 channel f-MUX for South Pole Telescope
• Extend to more channels
• (Submitted to Appl. Phys. Lett.)