Bolometer Group
description
Transcript of Bolometer Group
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
Attowatt NEP in dc experimentsAttowatt NEP in dc experiments
Both, Quasiparticle multiplier, 1987 Both et al., Quasiparticle transistor, 1999
Cascade Quasiparticle Amplifier Cascade Quasiparticle Amplifier and CEBand CEB
A
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