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