/
Basic Detection Techniques Basic Detection Techniques

Basic Detection Techniques - PowerPoint Presentation

marina-yarberry
marina-yarberry . @marina-yarberry
Follow
363 views
Uploaded On 2018-11-07

Basic Detection Techniques - PPT Presentation

Frontend Detectors for the Submm Andrey Baryshev Lecture on 17 Oct 2011 Basic Detection Techniques Submm receivers Part 3 2 Outline Direct detectors principle Photodetectors ID: 720319

detection tes basic submm tes detection submm basic techniques part receivers noise detector nep detectors power signal thermometer high

Share:

Link:

Embed:

Download Presentation from below link

Download Presentation The PPT/PDF document "Basic Detection Techniques" is the property of its rightful owner. Permission is granted to download and print the materials on this web site for personal, non-commercial use only, and to display it on your personal computer provided you do not modify the materials and that you retain all copyright notices contained in the materials. By downloading content from our website, you accept the terms of this agreement.


Presentation Transcript

Slide1

Basic Detection TechniquesFront-end Detectors for the Submm

Andrey

Baryshev

Lecture on

17 Oct 2011Slide2

Basic Detection Techniques – Submm receivers (Part 3)

2

Outline

Direct

detectors (principle)

Photo-detectors

Bolometers

Other types (pyro-detectors,

Golay

cell)

Noise in direct detectors

NEP -- noise equivalent power

Photon noise

Electronics noise

Low noise detectors in

submm

THz region

Transition edge sensors

Kinetic inductance detectors

SIS junction as direct

detector

TES bolometer

Practical measurement of NEPSlide3

Basic Detection Techniques – Submm receivers (Part 3)

3

Direct detector principles

Direct detector gives signal proportional to the power of incoming radiation or amount of photons.

Usually detector pixel is much simpler than heterodyne counterpart, so large arrays are possible

Photo detector (electronic)

Bolometric principle

(thermal

detectors)

Coherent detectors (diode)

Other principlesSlide4

Basic Detection Techniques – Submm receivers (Part 3)

4

Parameters of direct detectors

Quantum efficiency

Noise

Linearity

Dynamic range

Number and size of pixels

Time response

Spectral response

Spectral bandwidthSlide5

Basic Detection Techniques – Submm receivers (Part 3)

5

NEP

NEP is

power

at the input of the detector to produce

SNR=1

One can add the contributions of different noise sources

in square

fashion

as in the formula

above

for optics noise

contributionSlide6

Basic Detection Techniques – Submm receivers (Part 3)

6

Photon noise and Johnson noise

Detector is limited by statistics of incoming photons

2hc(kT)

1/2

ηλ

qGR

1/2

NEP =

Detector is limited by Johnson noise (thermal fluctuations)

2hc(1/t)

1/2

λ

η

1/2

NEP =Slide7

Basic Detection Techniques – Submm receivers (Part 3)

7

Black body facts

Photon occupation numbers

Uncertainty in

photon numbers

Photon NEP

Stefan-Boltzmann law

M =

σ

T

4

Φ

= 4

π

R

2

L

L= e (2 h f

3

)/(c/n)

2

/(

Exp

(

hf

/(

kT

))-1)Slide8

Basic Detection Techniques – Submm receivers (Part 3)

8

Photo detectors

Arriving photon generate/modify free charge carriers distribution

Classical semiconductor (utilizing band gap)

It has a lower frequency limit

hF

>

E

gap

Typical semiconductor work in IR region

By applying stress to the crystal, it is possible to decrease

E

gap

Like in stressed germanium

SIS junction

No low frequency limit (effective band gap modified by bias point)

High frequency limit due to gap structureKinetic inductance detectors

Photons break Cupper pairsIt has low frequency limit

hF > Egap

ESlide9

Basic Detection Techniques – Submm receivers (Part 3)

9

Example

Detectors PACS instrument on Herschel,

Stressed

germanium bolometersSlide10

Basic Detection Techniques – Submm receivers (Part 3)

10

2

1

CPW Through line

CPW ¼

Resonator

Coupler

Antenna

substrate

Central conductor

100

m

L= 5 mm @ 6 GHz

Al ground plane

Readout signal ~GHz

2

1

KID arrays for Astronomy

Principle of Kinetic Inductance Detection

Pair breaking detector

Superconductor ~ L

KIN

at T<Tc/3

L

KIN

~ N

qp

~ power absorbed

Use L

KIN

to measure absorbed power

KID

a SC material in resonance circuit

read out at F

0

~ 4 GHz

resonance feature is function of N

qp

signal in S

21

or R and

θSlide11

Basic Detection Techniques – Submm receivers (Part 3)

11

KID arrays

KID radiation coupling

Antenna in focus of Si lens

Herschell band 5 & 6

Radiation from sky F

RF

>>2

Δ

/h

-> increases N

qp

-> change in S

21

or R and

θ

F

0

<< F

RF

antenna << resonator

F

0

<< 2Δ/h No qp creation due to readout

Radiation

Si Lens

2

1

CPW Through line

CPW ¼

Resonator

Coupler

Antenna

substrate

Central conductor

100

m

L= 5 mm @ 6 GHz

Al ground plane

Most sensitive area

Readout signal ~GHz

2

1Slide12

Basic Detection Techniques – Submm receivers (Part 3)

12

KID arrays

Principle of KID arrays

Resonances @ F

0

F

0

set by geometry (length)

Intrinsic FDMSlide13

Basic Detection Techniques – Submm receivers (Part 3)

13

KID arrays for astronomy

General idea for the FP

Optical Interface

flies eye array of Si lenses, size 20

F

λ

/2.

90.6% packing efficiency in hexoganal

Array

Detectors printed on back Si lens array

Readout

4 SMA coax connectors

2 full chains -> redundancy

~5000 pixel

0.48 mmSlide14

Basic Detection Techniques – Submm receivers (Part 3)

14

KID focal plane for NIKA

400 pixel test array for 2 mm

antenna

KID

Through lineSlide15

Basic Detection Techniques – Submm receivers (Part 3)

15

Pair breaking detector: fundamental sensitivity limit

DOS

e-p coupling

# quasiparticles

quasiparticle lifetime

1 sec

Pmax/NEP>10.000Slide16

Basic Detection Techniques – Submm receivers (Part 3)

16

Measuring Dark NEP

~

IQ

Synthesizer

Quadrature mixer

Re

Im

ADC

analyses

Superconductor

Shorted end

Open end,

coupler

1

2

Cryostat

LNA

Measure bare resonators

Measure all ingredienst of NEP

Quasiparticle lifetime 

qp

noise S

x

Quasiparticle response

δ

x/

δ

N

qp

For R and

θ

Noise Signal qp roll-off

θ

or RSlide17

Basic Detection Techniques – Submm receivers (Part 3)

17

SIS photon detector

17

photon

Δ

E

E

F

qV

High sensitive in far-IR – sub-mm region

q

: elementary charge

h:

plank constant

ν

:frequency

I

sg

: subgap current

η

:

quantum efficiency

Superconductor

Bias voltage,

V

Insulator

Superconductor

@ 600 GHz

Our goal:

Current status: 10

-16

10

-17

W/

Hz

SIS junction

Density of statesSlide18

Basic Detection Techniques – Submm receivers (Part 3)

18

Comparison with theoretical value

(1)

10/17/2011

18

4.2 K

1.6 K

Bias voltage [ V ]

Current [ A ]

D(E)

:density of states,

F(E)

: Fermi function, Δ: gap energy

Nb

/Al-

AlN

/

Nb

junction

Tinkham

(1975)

Theoretical curvesSlide19

Direct

Detection

of

Radiation

Best

Sensitivity

direct

Detection

&

low

Temperatures

Bandpass

Filter (Absorber,

Antenna)

Detector Amplifier

Signal

Filter

Output

Noise:

Noise

Equivalent

Power

(

NEP

)  T

Energy

Resolution:

2

1

0

2

1

2

ln

2

2

-

¥

÷

÷

ø

ö

ç

ç

è

æ

×

=

D

ò

df

NEP

ESlide20

Spectral Bandwidth

:

Absorber and Coupling to Thermometer

very high:

l

~ 10

-3

m...10

-12

m

E

Ph

~ meV...MeV

Thermal Conductance G to bath T

Bath

= const.

Thermometer

Absorber with Heat

Capacitance C

D

T =

f

( C, G, E

Ph

,

F

Ph

)

t

Th

=

f

( C, G,… )

Incident Radiation

E

Ph

,

F

Ph

,

t

Ph

C (

T/

t) + G (T

TES

- T

Bath

) = P

Abs

(t) + P

Meas

(t)

Slide21

t

Th



t

Ph

:

“Quantum Calorimeter“

Thermal Conductance G to bath T

Bath

= const.

Thermometer

Absorber with Heat

Capacitance C

D

T =

f

( C, G, E

Ph

,

F

Ph

)

t

Th

=

f

( C, G,… )

Incident Radiation

E

Ph

,

F

Ph

,

t

Ph

t

Th



t

Ph

:

“Bolometer“

C (

T/

t) + G (T

TES

- T

Bath

) = P

Abs

(t) + P

Meas

(t)

Slide22

Operation at low Temperatures

4.2 K

for high signal & fast detector for low noise power:

D

T

 ,

t

Th

C

NEP

= 4 k

B

T

2

G

G 

C , G

 T

n

, n > 1

Quantum Calorimeter

Bolometer

D

T

=

(

E

Ph

/

C

)

1/(1 - i

/

w

t

Th

)

D

T

=

(

F

Ph

/

G

)

1/(1 + i

w

t

Th

)

Energy dispersive detection of Power sensitive detection

rapid temperature change of quasi-dc photon flux Slide23

Thermometer:

high sensitivity & high dynamic range

compatible with T

4.2 K

& low power dissipation

transducer temperature

electrical signal

Superconducting Phase Transition Thermometer

Transition Edge Sensor (TES)

TES Thermometer

Thermometer

Absorber C

T

Bath

Low-

Tc

Superconductors

Nb

 9K

Al

1K

Mo

0.92 K

Ti

 0.4 K

Ir

 150 mK

W

15 mK...150mK

Slide24

TES Thermometer

TES Thermometers:

high & positive

a

sensitive temperature-to-resistance transducers

low ohmic, i.e., voltage bias & current readout

negative

Electro-Thermal-Feedback

Resistive Thermometers

R = R

0

T

n

a

= (T/R)

R

/

T = n

T < 4.2K:

TES:

a

10...1000

Normal Metals:

a

0.001

Semiconductor:

a

-0.1..-1Slide25

TES Thermometer with ETF

Negative Electro-Thermal Feedback

Linearized

TES response:

D

P

ABS

=

-

D

P

Joule

(for very strong n-ETF)

Faster

TES response:

t

Th

ETF

3 (C/G) /

a

(Calorimeter count rate )

„Voltage Bias“

R

TES

V

TES

=const.

I

TES

T

TES

P

Joule

/

T

< 0

negative

ETF

in transition region:

D

P

ABS

D

T

D

R

TES

P

Joule

= - I

TES

V

TES

a

T

/

T

TES

C (

T/

t)

+

G (T

TES

- T

Bath

) =

P

ABS (t)

+ PJoule (t) Slide26

TES readout with SQUIDs

R

TES

I

Bias

R

Bias

D

I

TES

SQUIDs

:

current

sensor for TESs

low temperature compatible,

low power dissipation

(<1nW)

highly sensitive

(

pA

resolution)

& high bandwidth

(dc – MHz)

Elektrisches

Signal

@ 300K

<4K

Voltage Bias: R

Bias

<< R

TES

R

TES

1m

W

…100m

W

(Cryogenic) current sensor: Z

Noise

R

TESSlide27

Basic Detection Techniques – Submm receivers (Part 3)

27

Transition edge sensor principle

Thin superconducting film as thermometer

Square law power detector

thermal time constant t = C/G

C: thermal capacitance

G: thermal conductivitySlide28

LABOCA (as example)Basic Detection Techniques – Submm receivers (Part 3)

28Slide29

Space TES detectors (SPICA, SAFARI)Basic Detection Techniques – Submm receivers (Part 3)

29

Low G TES

High G TESSlide30

Basic Detection Techniques – Submm receivers (Part 3)

30

Procedure of an NEP measurement

Determine the signal power

It is given by Planck formula

Need temperature of calibrator black-bodies

Frequency coverage of the detector (measured by FTS)

Knowledge of solid angle of antenna beam pattern

Determine the responsively

Measure response from hot/cold radiators

Calibrate detector output in input power units

Determine the background noise

Block connect the detector beam to as little background –possible

Measure time trace and using responsively and integration time express it in NEP Wt/Hz

1/2