Transcript No Slide Title

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)
 Comparison with TES
 NEP with background load
 General Ultimate NEP formula
 Experiments
 Possible developments
 Conclusions

Detector requrements
for future space telescopes
SPIRIT, 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 !?
Cold-Electron Bolometer (CEB) with Capacitive Coupling and
Thermal Isolation by Tunnel Junctions
CEB with Electrothermal Feedback (ETF)
Current responsivity:
I
I / T
I / T
L
Si 


,
P Gcool  Ge  ph  iC
Gcool ( L  1)1  i 
L  Gcool Ge  ph  1
   0 ( L  1)
 0  C Ge  ph
- ETF gain
- effective time constant ( ~10 ns)
- e-ph time constant (~ 10 ms at 100 mK)
CEB. Cooling Thermal Conductance
12
10
8
P = 0 .1 p W
0
6
Te
4
2
Te
P =0
0
0
0
0 .0 5
0.1
0 .1 5
0 .2
0 .2 5
Tph Temperature (K)
0 .3
0 .3 5
0 .4
Output Power
1.5
Ps = Pcool + Pe-ph
Pe-ph
TES
Ptot=Pbias+Ps
Output
power
-Pbiasz Ps
1
Saturation Power
Psat > 100 pW
(corresponds to
Tc=1.2 K)
Pbias0
0.5
CEB
Saturation Power
Output
Psat = 1 pW
power
Pcool z Ps
0
0
0.5
1
Signal Power, Ps (pW)
1.5
TES and CEB. Operating Temperature
0.6
TES - "Tc -detector"
Tc
0.5
dc bias
heating
0.4
NEP
2
e-ph
0.3
0.2
2
= 4kT G
e
CEB - "0 -detector"
T
bath
0.1
cooling
0
0
0.5
1
Signal Power, P (pW)
1.5
Turning Point from ”Heating” to ”Cooling
Transition Edge Sensor (TES)
Te could be decreased by
direct electron cooling (!) :
Te should be even more increased by
dc bias heating (!) :
P0
Ptotal = P0 + Pbias ,
- removed by SIN junctions
Te heat > Te = 230 mK
Te cool << Te = 230 mK
time
time
?
Te cool
0
P bias = Pmax signal
100 mK
Tph
Pbias - heating!
?
P0
Te heat
P0
230 mK
Te
0
100 mK
Tph
230 mK
Te
Electron-Phonon Noise
Equilibrium case:
NEPe-ph2 = 4 kBT2 Ge-ph = 20 kB SV T6
V- volume
Nonequilibrium case:
(Jochum et al. – 1998)
5
Te = (Tph + P )1/5
SV
NEPe-ph2 = 10 kB SV (Tph6 + Te6)
Direct electron cooling
SIN junction noise
2
NEPSIN

I
2
SI
2
Shot noise
2
P I
SI
 P
Correlation term
For strong electron cooling:
2
Heat flow
noise
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
General Ultimate NEP Formula
General NEPshot - dominates
Kuzmin, Madrid - 2003
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
NEP e-ph. Normal metal and Superconducting absorbers
Limit 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, TD = 2 K (Al, D200 meV)
NEPshot = 7*10 –19 W/Hz1/2
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
Electron Cooling and NEP measurements
I. Agulo, L. Kuzmin and M. Tarasov
Strip width  0.2 mm
Attowatt NEP in dc experiments


Both, Quasiparticle multiplier, 1987
Both et al., Quasiparticle transistor, 1999
Cascade Quasiparticle Amplifier
and CEB
A
Conclusions:
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 Bolometer with
Strong Electrothermal Feedback