Superconducting Kinetic Inductance Detectors with Microwave Readout

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Superconducting Kinetic Inductance Detectors with
Microwave Readout
Peter Day, Rick LeDuc Jet Propulsion
Laboratory Jonas Zmuidzinas, Ben Mazin, Tasos
Vayonakis Caltech
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Kinetic Inductance Effect

• For AC fields
• Finite kinetic energy stored in supercurrent
  (motion of Cooper pairs)
• Must apply electric field to change supercurrent
• kinetic inductance effect surface reactance
  Xs iwm0leff

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Change in Xs with nqp
For T ltlt Tc
Variation of K.I. With Nqp is roughly constant at
low temperature.
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Measurement of Kinetic Inductance with a
Microwave Resonator
l/2
l/4
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Readout noise
Q
Compare to amplifier phase noise
I
For TN20K, P1pW 10-5 rad/hz1/2
Readout noise (Qs50,000 V5000mm3) 3
q.p./ hz1/2
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A Test Device
0.22mm aluminum on sapphire 3mm 10 Ghz
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X-Ray Events
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Thermal Calibration of Sensitivity

• Measure response to temperature changes
• thermally excited quasiparticles

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Noise Measurements
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Multiplexing
Frequency domain muliplexing Excite with a
comb Can use single cryogenic amplifier Nmult
Q/20
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Quasiparticle Trapping
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An X-ray Detector
Tantalum absorber with aluminum
detectors. Multiplexed (2 chan.) readout.
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Some Preliminary Results
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Conclusions

• Understand detector responsivity
• Demonstrated multiplexed readout
• Demonstrated useful coupling of radiation
  into the detector
• Not yet at projected sensitivity
• but not very far from S.O.A.

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Energy Spectrum
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Decay Times
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A Small Array
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Readout Circuit