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Ultimate Cold-Electron Bolometer
with Strong Electrothermal Feedback
Leonid Kuzmin
Chalmers University of TechnologyBolometer GroupBolometer Group
Björkliden - 2004
Through the thorns to the stars!
Igenom törnen mot stjärnorna!
Через тернии к звездам!
OutlineOutline
Cold-Electron Bolometer (CEB) Comparison with TESNEP with background loadGeneral Ultimate NEP formulaExperimentsPossible developmentsConclusions
Noise Equivalent power less than 10-20 W/Hz1/2 !?
Wavelengths: submillimeter/infrared bands: 40-500 m.
100x100 pixel detector arrays !?
Readout electronics with multiplexing (SQUID?)
Ideal detector: counting individual photons and providing some energy discrimination !?
Detector requrements Detector requrements for future space telescopesfor future space telescopes
SPIRIT, SPECS, …SPIRIT, SPECS, …
Cold-Electron Bolometer (CEB) Cold-Electron Bolometer (CEB) withwith Capacitive Coupling and Capacitive Coupling and Thermal Isolation by Tunnel JunctionsThermal Isolation by Tunnel Junctions
Current responsivity:
CEB with Electrothermal Feedback (ETF)CEB with Electrothermal Feedback (ETF)
[ ],1)1(
//
ωτω iL
L
G
TI
CiGG
TI
P
IS
coolphecooli ++
∂∂=
++
∂∂=
∂
∂=
Λ−
- effective time constant ( ~10 ns)
1>>= −phecool GGL - ETF gain
)1(0 += Lττ
- e-ph time constant (~ 10 s at 100 mK)pheGC −Λ=0τ
CEB. Cooling Thermal ConductanceCEB. Cooling Thermal Conductance
P0= 0
Tph
P0=0.1 pW
Te
0
2
4
6
8
10
12
0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4
Temperature(K)
Te
Output PowerOutput Power
0
0.5
1
1.5
0 0.5 1 1.5
Pcool z Ps
Outputpower
Pe-ph
Ps = Pcool + Pe-ph
Outputpower
Pbias0
Saturation Power Psat = 1 pW
Saturation Power Psat > 100 pW
(corresponds to Tc=1.2 K)
Signal Power, Ps (pW)
TES
CEB
Ptot=Pbias+Ps
-Pbiasz Ps
TES and CEB. Operating TemperatureTES and CEB. Operating Temperature
0
0.1
0.2
0.3
0.4
0.5
0.6
0 0.5 1 1.5
Signal Power, P (pW)
TES - "Tc -detector"
CEB - "0 -detector"
NEPe-ph
2 = 4kTe
2G
Tbath
dc bias heating
cooling
Tc
Turning Point from ”Heating” to ”CoolingTurning Point from ”Heating” to ”Cooling
Te could be decreased bydirect electron cooling (!) :
P0 - removed by SIN junctions
Te cool << Te = 230 mK
P0
Tph
Te100 mK 230 mK
time
Pbias - heating!
P0
TphTe100 mK 230 mK
time
Transition Edge Sensor (TES)
Te should be even more increased bydc bias heating (!) :
Ptotal = P0 +Pbias , Pbias = Pmax signalTe heat > Te = 230 mK
0 0
? ?Te heat
Te cool
Electron-Phonon NoiseElectron-Phonon NoiseEquilibrium case:
NEPe-ph2 = 4 kBT2 Ge-ph = 20 kBV T6
V- volume
Nonequilibrium case: (Jochum et al. – 1998)
NEPe-ph2 = 10 kBV (Tph
6 + Te6)
Direct electron cooling
Te = (Tph5 + P
V)1/5
SIN junction noiseSIN junction 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
22
22 2 ω
ωωω δδδδ PS
IPSINEP
IISIN +−=
Shot noise Correlation term Heat flow noise
General Ultimate NEP FormulaGeneral Ultimate NEP Formula
NEPshot = ( 2 P0 Equant )1/2
P0 – background power load
Equant – energy level of P0 quantization
Equant = kB Te - normal metal absorber
Equant = - superconducting absorber
Kuzmin, Madrid - 2003General NEPshot - dominates
NEP e-ph.NEP e-ph. Normal metalNormal metal and and SuperconductingSuperconducting absorbers absorbers
Limit NEP for different bolometersLimit NEP for different bolometers
NEPshot = ( 2 P0 Equant )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, = 2 K (Al,
00eV) NEPshot = 7*10 –19 W/Hz1/2
General Limit NEP formulaGeneral Limit NEP formulaSystems 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
Electron Cooling and NEP measurementsElectron Cooling and NEP measurements I. Agulo, L. Kuzmin and M. TarasovI. Agulo, L. Kuzmin and M. Tarasov
Strip width0m
Conclusions:Conclusions:We propose the
-- simplest-- smallest (< 2 m) -- 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 Bolometer with Strong Electrothermal Feedback