Ultimate Cold-Electron Bolometer

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Bolometer Group
Through the thorns to the stars! Igenom törnen
mot stjärnorna! ????? ?????? ? ???????!
Chalmers University of Technology

• Ultimate Cold-Electron Bolometer
• with Strong Electrothermal Feedback

Leonid Kuzmin
Björkliden - 2004
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Outline

• Cold-Electron Bolometer (CEB)
• Comparison with TES
• NEP with background load
• General Ultimate NEP formula
• Experiments
• Possible developments
• Conclusions

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Detector requrements for future space
telescopesSPIRIT, SPECS,

• Noise Equivalent power less than 10-20 W/Hz1/2 !?
• Wavelengths submillimeter/infrared bands 40-500
  mm.
• 100x100 pixel detector arrays !?
• Readout electronics with multiplexing (SQUID?)
• Ideal detector counting individual photons and
  providing some energy discrimination !?

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Cold-Electron Bolometer (CEB) with Capacitive
Coupling and Thermal Isolation by Tunnel Junctions
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CEB with Electrothermal Feedback (ETF)
 
Current responsivity  
- ETF gain
- effective time constant  ( 10 ns)
- e-ph time constant ( 10 ms at 100 mK)
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CEB. Cooling Thermal Conductance
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Output Power
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TES and CEB. Operating Temperature
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Turning Point from Heating to Cooling
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Electron-Phonon Noise
Equilibrium case    NEPe-ph2 4 kBT2 Ge-ph
20 kB SV T6 V- volume  Nonequilibrium
case (Jochum et al. 1998)
  NEPe-ph2 10 kB SV (Tph6 Te6)
Direct electron cooling
S
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SIN junction noise
Shot noise Correlation term Heat flow noise
For strong electron cooling Pcool gtgt
Pe-ph   NEPshot ( 2 P0 kB Te )1/2 P0
background power load For P0 0.1 pW, Te 50
mK, NEPshot 410 19 W/Hz1/2
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General Ultimate NEP Formula
Kuzmin, Madrid - 2003
General NEPshot - dominates
NEPshot ( 2 P0 Equant )1/2
P0 background power load Equant energy level
of P0 quantization Equant
kB Te - normal metal absorber Equant D
- superconducting absorber
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NEP e-ph. Normal metal and Superconducting
absorbers
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Limit NEP for different bolometers
NEPshot ( 2 P0 Equant )1/2 CEB P0 10 fW,
Te 50 mK, NEPshot 110 19 W/Hz1/2 TES
P0 10 fW, Te 500 mK, NEPshot 410 19
W/Hz1/2 Kinetic Ind. Det P0 10 fW, TD 2 K
(Al, D200 meV) NEPshot 710 19 W/Hz1/2
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General Limit NEP formula

• Systems with linear on T thermal conductance
• Spider-web TES with conductance through the
  legs
• CEB with cooling through SIN tunnel junctions
  (weak dependence on T G T1/2),

NEPshot 2 P0 Equant

• Systems with dominant e-ph thermal conductance
• (strong nonlinearity on T Ge-ph T4 )
• all bolometers on plane substrates with e-ph
  conductance
• antenna-coupled TES on chip,
• NHEB with Andreev mirrors

NEPshot e-ph 10 P0 Equant
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Electron Cooling and NEP measurements I. Agulo,
L. Kuzmin and M. Tarasov
Strip width 0.2 mm
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Attowatt NEP in dc experiments
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• Both, Quasiparticle multiplier, 1987
• Both et al., Quasiparticle transistor, 1999

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Cascade Quasiparticle Amplifier and CEB
A
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Conclusions
We propose the -- simplest -- smallest (lt 2 mm)
-- coldest (Te lt Tph) -- fastest( 10 ns) - --
most sensitive (under real background Po) -- not
saturated (up to Tc of electrodes, gt100 pW) --
ideal 0-detector (could not be better!) --
easy multiplied on plane substrate (for large
arrays) -- easy amplified by Cascade
Quasiparticle Amplifier -- easy multiplexed by
SQUIDs -- easy fit in any experiment (from submm
to near-IR) Cold-Electron Bolometer with
Strong Electrothermal Feedback