Characterization of noise and transition shapes in superconducting transition-edge sensors using a...
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Characterization of noise and transition shapes in superconducting transition-edge sensors using a
pulsed laser diode
Dan SwetzQuantum Sensors Group NISTBoulder, CO
Joel UllomDoug BennettRandy DorieseGene HiltonKent IrwinCarl ReintsemaDan Schmidt
Goal: Develop a systematic way to combine TES measurements and optimally constrain TES models
Only when we understand out detectors can we predict their behavior and optimize their performance
How to Characterize TESs?
RSh GTES RN n TC CTES β α
M
ΔE
C2-BodyG2-Body
1-Body Model 2-Body Model
Complex Z Pulses NoiseIV vs Tbath
Power Law Fits
Parameters:
Measurements:
Models:
New Parameters:
1550 nm laser:• 0.8 eV/photon
(1 keV pulse = 1,200 photons)
• Computer controlled
Variable Attenuator
Vacuum Jacket
Laser
Fiber
3K Cold Attenuator
Ferrule Flange
Detector
50 mK box Collimator
The Diode Laser: A new tool for X-ray TES characterization
New Capabilities using Laser Pulses
•Pulses on demand•Many trigger options•Large range of possible energies •Reliable low energy pulses
Detector Linearity
10,000 averaged pulses
Time (ms)
Detector Response vs Pulse Energy
2 4 6 8 10 12 14 16
0 1 2 3 4 5
Log
Det
ecto
r Res
pons
e (V
)
-14
-12
-10
-8
Time (ms)
Pulse Response above TC
Det
ecto
r Res
pons
e (m
V)
0
10
30
20
0
10
30
20
40
Pul
se P
eak
(mV
)
Pulse Energy (keV)0 2 4 6 8 10 12 14
The Test Detector•350 μm square Mo/Cu bilayer
0.1 μm-thick Mo0.2 μm-thick Cu
•7 interdigitated normal Cu bars0.5 μm thick90% TES length
•bismuth film absorber1.5 μm thick
•600 μm SiN frame0.5 μm thick
•Overlapping perforations in SiN membrane to control GTES
350 m
600 m
perforations Interdigitated normal bars
Goal: An optimized TES for materials analysis at 7 keV*
* Doriese 1EX07
Cur
rent
TES Modeling and Characterization
Questions:1.Are TESs 1-body (simple) or 2-body (dangling) ?2.What are the effects on parameters?
3.Can the dangling body explain (part of) the unexplained excess high-frequency noise?
Hypothesis: SiN is adding a dangling 2nd body
Estimate from geometry*: Cdangling ~ 0.1 pJ/K, ~ 5% of CTES
* K. Rostem, et. al, Proc. SPIE, 7020, 70200L (2008)
Simple TES
Dangling TES
Parameter Extraction Methodology
SC Noise IV vs Tbath
Power Law FitsPulses
above Tc
RSh 260 uΩ
GTES 118 pW/K
RN 10.7 mΩ
n3.3
TC 109 mK
CTES 1.7 pJ/K
RSh
GTES
RN
n
TC
CTES
β
α
M
ΔE
Cdangling
Gdangling
Parameter Extraction Methodology
SC Noise IV vs Tbath
Power Law FitsPulses
above Tc
RSh 260 uΩ
GTES 118 pW/K
RN 10.7 mΩ
n3.3
TC 109 mK
CTES 1.7 pJ/K
RSh
GTES
RN
n
TC
CTES
Measurements at 10—80 % bias of Rnormal in steps of 10%
Complex Z Pulsesβ Noise
α
M
ΔE
Cdangling
Gdangling
β
Parameter Extraction Methodology
SC Noise IV vs Tbath
Power Law FitsPulses
above Tc
RSh 260 uΩ
GTES 118 pW/K
RN 10.7 mΩ
n3.3
TC 109 mK
CTES 1.7 pJ/K
RSh
GTES
RN
n
TC
CTES
β
α
M
ΔE
Cdangling
Gdangling
Complex Za Pulsesbβ
Measurements at 10—80 % bias of Rnormal in steps of 10%
αpulseαCZGoF
pulseGoFCZ
Cdangling Gdangling
Dangling Model
a) Bennett et. al., Proc. AIP, vol. 1185. pp 737-40, (2009) b) Bennett et. al., APL submitted (2010)
FGoodness of Fit
Phase Space
Parameter Extraction Methodology
SC Noise IV vs Tbath
Power Law FitsPulses
above Tc
RSh 260 uΩ
GTES 118 pW/K
RN 10.7 mΩ
n3.3
TC 109 mK
CTES 1.7 pJ/K
RSh
GTES
RN
n
TC
CTES
β
α
M
ΔE
Cdangling
Gdangling
Complex Za Pulsesbβ
Measurements at 10—80 % bias of Rnormal in steps of 10%
αpulseαCZGoF
pulseGoFCZ
Cdangling Gdangling
Dangling Model
FNoise
GoFnoise
M
Goodness of FitPhase Space
a) Bennett et. al., Proc. AIP, vol. 1185. pp 737-40, (2009) b) Bennett et. al., APL submitted (2010)
Parameter Extraction Methodology
SC Noise IV vs Tbath
Power Law FitsPulses
above Tc
RSh 260 uΩ
GTES 118 pW/K
RN 10.7 mΩ
n3.3
TC 109 mK
CTES 1.7 pJ/K
RSh
GTES
RN
n
TC
CTES
β
α
M
ΔE
Cdangling
Gdangling
Complex Za Pulsesbβ
Measurements at 10—80 % bias of Rnormal in steps of 10%
αpulseαCZGoF
pulseGoFCZ
Cdangling Gdangling
Dangling Model
Noise
GoFnoise
M ΔEa) Bennett et. al., Proc. AIP, vol. 1185. pp 737-40, (2009) b) Bennett et. al., APL submitted (2010)
Goodness of FitPhase Space
Pulse Fits
•Simple model GoF = 1.58•Dangling model achieves GoF = 14•High Cdang, Gdang excluded
Why 2d GoF phase space?Exclude local minimaPoor estimate of error on data
Good Fit
Bad Fit
Departure from simple model at 1.5 ms
Goodness of Fit: CZ and Noise
•Simple model noise GoF = 11.3•Dangling model achieves GoF =24
Good Fit
Bad Fit
Good Fit
Bad Fit
•Simple model CZ GoF = 4.5•Dangling model achieves GoF = 6.4
Large parameter space excluded, particularly high Cdang, Gdang regions. Reasonable constraints on both Cdangling and Gdangling
α and M are largely unaffected by dangling parameters
1-body model predicts αpulse = 310, αCZ = 314 and M = 1.52Conclusion: Can estimate using simple model
α M
Nearly identical values from CZ fits
Dangling Body Affects Noise and Energy Resolution
Dangling noise explains increased mid-frequency noise at ~100-1000 Hz
2.28 eV = Simple model energy resolution 2.34 eV = Simple model with CTES + Cdangling
2.5—3.1eV = Dangling model energy resolution
M-noise
Dangling noise degrades resolution by ~ 10--30%
ΔE
bad fit region
Conclusions and Future Plans
• Diode laser is a useful tool for device characterization
• Device is described by a dangling two-body model
• Dangling parameters have minimal affect on alpha and excess noise
• Dangling body significantly degrades energy resolution
• Repeat analysis on more devices
Similar 9-bar deviceΔEFWHM = 3.64 eV
Very preliminary spectrum of Mn Kα
Fin
Energy Resolution vs Gdangling
Gdangling
Pulse FitsEvidence for
dangling models •Dangling model fits data well•Requires High S/N – 4000 pulses averaged
Simple model:• overshoots data at early times• undershoots data at late times