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Bolometer Group

Through the thorns to the stars! Igenom törnen mot stjärnorna! Через тернии к звездам !. Bolometer Group. Chalmers University of Technology. Ultimate Cold-Electron Bolometer with Strong Electrothermal Feedback. Leonid Kuzmin. Björkliden - 2004. Outline. Cold-Electron Bolometer (CEB)

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Bolometer Group

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  1. Through the thorns to the stars! Igenom törnen mot stjärnorna! Через тернии к звездам! Bolometer Group Chalmers University of Technology Ultimate Cold-Electron Bolometer with Strong Electrothermal Feedback Leonid Kuzmin Björkliden - 2004

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

  3. 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 !?

  4. Cold-Electron Bolometer (CEB) withCapacitive Coupling and Thermal Isolation by Tunnel Junctions

  5. CEB with Electrothermal Feedback (ETF) Current responsivity: - ETF gain - effective time constant  ( ~10 ns) - e-ph time constant (~ 10 ms at 100 mK)

  6. CEB. Cooling Thermal Conductance

  7. Output Power

  8. TES and CEB. Operating Temperature

  9. Turning Point from ”Heating” to ”Cooling

  10. 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 Electron-Phonon Noise S

  11. SIN junction noise Shot noise Correlation term Heat flow noise For strong electron cooling:Pcool >> Pe-ph NEPshot= ( 2 P0 kB Te )1/2 P0 – background power load For P0 = 0.1 pW, Te = 50 mK, NEPshot= 4*10 –19 W/Hz1/2

  12. General Ultimate NEP Formula Kuzmin, Madrid - 2003 General NEPshot- dominates NEPshot= ( 2 P0Equant)1/2 P0 – background power load Equant– energy level of P0 quantization Equant = kB Te- normal metal absorber Equant = D- superconducting absorber

  13. NEP e-ph.Normal metal and Superconducting absorbers

  14. Limit NEP for different bolometers NEPshot= ( 2 P0Equant)1/2 CEB:P0 = 10 fW, Te = 50 mK, NEPshot= 1*10 –19 W/Hz1/2 TES:P0 = 10 fW, Te = 500 mK, NEPshot= 4*10 –19 W/Hz1/2 Kinetic Ind. Det: P0 = 10 fW, TD= 2 K (Al, D=200 meV)NEPshot= 7*10 –19 W/Hz1/2

  15. 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), • … General Limit NEP formula NEPshot= 2 P0Equant • 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 P0Equant

  16. Electron Cooling and NEP measurementsI. Agulo, L. Kuzmin and M. Tarasov Strip width = 0.2 mm

  17. Attowatt NEP in dc experiments

  18. Both, Quasiparticle multiplier, 1987 • Both et al., Quasiparticle transistor, 1999

  19. Cascade Quasiparticle Amplifier and CEB A

  20. We propose the --simplest --smallest (< 2 mm) --coldest (Te < Tph) --fastest(~ 10 ns) - --most sensitive (under real background Po) --not saturated (up to Tc of electrodes, >100 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 Bolometerwith Strong Electrothermal Feedback Conclusions:

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