An introduction to radiation hard M onolithic A ctive P ixel S ensors Or :

1

An introduction to radiation hard

Monolithic Active Pixel Sensors Or:

A tool to measure Secondary Vertices

Dennis Doering*, Goethe University Frankfurt am Main

on behalf of the CBM-MVD-Collaboration

2

Outline- The challenge to measure Secondary Vertices- Operation principle of MAPS- Radiation damage effects- High Resistivity and radiation hardness- Conclusion

An introduction to radiation hard

Monolithic Active Pixel Sensors Or:

A tool to measure Secondary Vertices

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Task: Reconstruct Secondary Vertices

Dennis Doering: An introduction to MAPS Hades Summer School Prague Oct. 2011 3

Primary Beam: 25 AGeV Au Ions (up to 109/s)

Reconstruction concept for open charm

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Primaryvertex

Target(Gold)


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Primaryvertex

Target(Gold)


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Primaryvertex Secondary

vertexShort lived particle D0 (ct = ~ 120 µm)

Target(Gold)


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Detector 1Detector2Target

(Gold)

z


z= 5cm

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(Gold)

z= 5cm


1) Short life time:

- Good spatial resolution- low material budget (scattering)

2) Rare probe-> High statistics

- Fast - Radiation hard

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(Gold)

z


1) Short life time:




Is it possible to develop such a detector?Þ MAPS in CBM @ FAIR

z= 5cm

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Use digital cameras as particle detector






(Gold)

z


1) Short life time:





z= 5cm

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Use digital cameras as particle detector: MAPS






(Gold)

z


1) Short life time:





z= 5cm

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Operation principle


SiO2 SiO2 SiO2

N+ P+

P-

P+

Diode

Epitaxial Layer

P-Well

Substrate

e-

N+

e-

Particle

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Operation principle


SiO2 SiO2 SiO2

N+ P+

P-

P+

Diode

Epitaxial Layer

P-Well

Substrate

N+ 50µm

Thin and good spatial resolution

10-40µm => a few µm resolution

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Operation principle


SiO2 SiO2 SiO2

N+ P+

P-

P+

Diode

Epitaxial Layer

P-Well

Substrate

N+

10-40µm => a few µm resolution

50µm

Compare HADES MWPC:Drift cell „pitch“: few 1000µmResolution: few 100µm

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Radiation hardness?


Reconstruct up to 1000 tracks per collision and 1010 collisions per year

Fast readout and radiation hardness up to ~1013neq/cm² and ~1 MRad

Central Au + Au collision (25 AGeV)

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Classes of radiation damageTo be investigated and improved: Radiation hardness against…

… ionizing radiation:• Caused by charged particles and photons • Can ionize atoms and destroy molecules

… non-ionizing radiation:• Caused by heavy, charged and neutral,

particles• Atoms are displaced

Farnan I, HM Cho, WJ Weber, 2007. "Quantification of Actinide α-Radiation Damage in Minerals and Ceramics." Nature 445(7124):190-193.

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Non-ionizing radiation (Low Resistivity)


SiO2 SiO2

SiO2

N+ P+

P-

P+

Diode

Epitaxial Layer

P-Well

Substrate

N+

Defects generated by non-ionizing radiation.

e-

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The history of radiation hard MAPS


0 5 10 15 20 25 30 35 401011

1012

1013

1014

1015

Mimosa9 (2004)

Mimosa9 (2004)

Mimosa15 (2006)Mimosa18 (2008)

Low resistivity sensors Uncertainty range

Rad

iatio

n to

lera

nce

[neq

/cm

²]

Pixel pitch [µm]

Smaller pixel pitch => better radiation hardness

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High Resistivity


SiO2 SiO2

SiO2

N+ P+

P-

P+

Diode

Epitaxial Layer

P-Well

Substrate

N+

e-depletion

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Non-ionizing radiation (High resistivity)


SiO2 SiO2

SiO2

N+ P+

P-

P+

Diode

Epitaxial Layer

P-Well

Substrate

N+

depletion e-

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The history of radiation hard MAPS


0 5 10 15 20 25 30 35 401011

1012

1013

1014

1015

Mimosa9

Mimosa9

Mimosa15 (2006)Mimosa18 (2008)

Mimosa18 AHR (2011)

High resistivity sensors Low resistivity sensors Uncertainty range

Rad

iatio

n to

lera

nce

[neq

/cm

²]

Pixel pitch [µm]

Mimosa26 AHR (2010)

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Beam test @ CERN by IPHC Strasbourg


4 5 6 7 8 9 10 11 1293

94

95

96

97

98

99

100

Low Resistivity no irradiation High Resistivity no irradiation High Resistivity 1013n

eq/cm²E

ffici

ency

[%]

Threshold [mV]

Irradiated High Resistivity sensor: Better efficiency than unirradiated Low Resistivity sensor.

Threshold

Signal

Noise

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10

20

30

40

50

60

-34-27-15

Noi

se [e

]

Temperature [°C]-3

10

20

30

40

50

60

-34-27-15

Noi

se [e

]

Temperature [°C]-3

Noise increases

Sensor: - Mi-18 AHR, SB-Pixel, 10 µm pitch - Epitaxial layer: 400 W cm, 15 µm Irradiation: - fast reactor neutrons (Triga, Ljubljana) - Chip not powered during irradiation - Dose: 3 · 1014neq/cm² + O(3 MRad)

0 50 100 150 200 250 300 350 4000

1000200030004000500060007000

Ent

ries

[1 b

in=4

AD

C]

Charge collected [ADC]

<20% less entriesThinner active vol.?

CCE ok

Gain okFe-55 (X-rays)

0 500 1000 1500 2000 2500 3000 35000

500

1000

1500

2000

2500

3000

3500

Ent

ries

[1 b

in=4

AD

C]

Charge collected [e]

Ru-106 (b-rays)

99% det. eff.after irrad.

620e (MPV)

490e (MPV) <20% less signalThinner act. vol.?

Noise increases =>Compensate with cooling.

3 · 1014neq/cm² + O(3 MRad)Not irradiated

Limit of radiation hardness?

23Dennis Doering: An introduction to MAPS Hades Summer School Prague Oct. 2011 Preliminary conclusion: Sensor tolerates 3 · 1014neq/cm², to be confirmed in beam test

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- Forseen in ILC, STAR, CBM and ALICE- MAPS are the technology of choice for Open Charm in CBM- Requirements today not fully fulfilled, however ongoing research- Great improvements in the last few years and many ideas for future- Demonstrated excellent performance in beam test, even after 1013 neq/cm²- Sensor operational in laboratory even after 3·1014neq/cm²

Summary


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- Forseen in ILC, STAR, CBM and ALICE- MAPS are the technology of choice for Open Charm in CBM- Requirements today not fully fulfilled, however ongoing research- Great improvements in the last few years and many ideas for future- Demonstrated excellent performance in beam test, even after 1013 neq/cm²- Sensor operational in laboratory even after 3·1014neq/cm²

Summary


Conclusion: Monolithic Active Pixel Sensors A detector that YOU should know

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BACK-UP

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Column parallel sensors


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Column parallel sensors


Readout speed achieved: <100µsDesign goal for >2015: 30µsMaybe possible in future: <5µs

An introduction to radiation hard M onolithic A ctive P ixel S ensors Or :

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