Radiation hardness studies with combined irradiated MAPS

1

Radiation hardness studies with Radiation hardness studies with combined irradiated MAPScombined irradiated MAPS

Dennis Doering*1, Samir Amar-Youcef 1,3,Michael Deveaux1, Melissa Domachowski1, Ingo Fröhlich1, Christian Müntz1, Sarah Ottersbach1, Joachim Stroth1, Franz M Wagner2

1 Goethe University Frankfurt am Main, 2 TU München, Forschungsquelle Heinz Maier-Leipnitz (FRM II), 3 Helmholtz Research School, Frankfurt

Outline- MAPS and combined radiation- Influence on leakage current, CCE and noise- RTS as a fake hit source- Fake hit rate after combined radiation- Conclusion

*[email protected]

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Dennis DoeringDennis DoeringCBM-Collaboration Meeting CBM-Collaboration Meeting

Split 2009Split 2009

Radiation hardness studies with combined irradiated MAPSRadiation hardness studies with combined irradiated MAPS

2Expected radiation dose @MVDExpected radiation dose @MVD

The CBM-experiment (at FAIR)

The CBMMicro Vertex Detectorbased on MAPS

Expected radiation dose per CBM running-year:

How does a sensor chip react on such radiation doses?

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3ClassesClasses of radiation damageof radiation damage

To be investigated and improved: Radiation hardness against…

… ionizing radiation:• Energy deposited into the electron cloud• Can ionize atoms and destroy molecules• Caused by charged particles and photons

… non-ionizing radiation:•Energy deposited into the crystal lattice•Atoms are displaced•Caused by heavy (fast leptons, hadrons),charged and neutral particles

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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4Operation principle of MAPSOperation principle of MAPS

Reset+3.3V+3.3V

Output

SiO2 SiO2 SiO2

N++ N++N+ P+

P-

P+

Diode

Epitaxial Layer

P-Well

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5Operation principle of 3T-Pixel preamplifierOperation principle of 3T-Pixel preamplifier

C

Reset-Transistor

3.3V

Time

UK

K

IReset

ILeakage

particle

ISignal 0

1

2

3

Time

CDS=UK1- UK2

2

UK1

UK2

UK1

UK2

UK1

UK2

Threshold

Hit identified!

Measurementof leakage currentVariation: Noise

Joachim Stroth

Das CDS ist lokal in der Zeit. Die Grafik ist meines Erachtens irreführend. Auch ist laut Grafik das CDS mit Signal kleiner als ohne! Warum ist der Ladestrom "exponentiell" und der Leckstron "linear"?Erklärung dauert wahrscheinlich lange!SONST SEHR SCHÖN

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6Radiation tolerance against non-ionizing radiationRadiation tolerance against non-ionizing radiation

Reset+3.3V+3.3V

Output

SiO2

N++ N++N+ P+

P-

P+

SiO2

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7Leakage current due to non-ionizing radiationLeakage current due to non-ionizing radiation

Reset+3.3V+3.3V

Output

SiO2

N++ N++N+ P+

P-

P+

SiO2

Leakage current due to defects of non-ionizing radiation

immobile

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8Radiation tolerance against ionizing radiationRadiation tolerance against ionizing radiation

Reset+3.3V+3.3V

Output

SiO2

N++ N++N+ P+

P-

P+

SiO2Positive Charge

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9Leakage current due to ionizing radiationLeakage current due to ionizing radiation

Reset+3.3V+3.3V

Output

SiO2

N++ N++N+ P+

P-

P+

SiO2Positive Charge

Leakage current due to ionizing radiation

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10Radiation tolerance against combined radiationRadiation tolerance against combined radiation

Reset+3.3V+3.3V

Output

SiO2

N++ N++N+ P+

P-

P+

SiO2Positive Charge

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11Combined radiation: Possible additional leakage currentCombined radiation: Possible additional leakage current

Reset+3.3V+3.3V

Output

SiO2

N++ N++N+ P+

P-

P+

SiO2Positive Charge

Possible additional leakage current due to combined radiation:- produced by defects of nonionizing radiation- transported by fields of ionizing radiation

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12The measurement procedureThe measurement procedure

Goal: distinguish leakage current caused by different damagesStrategy: measure systematically leakage current of differently irradiated chips

1) Not irradiated => Reference

2) Irradiated with X-rays => Leakage current due to ionizing radiation3) Irradiated with neutrons => Leakage current due to non-ionizing radiation

4) Irradiated with X-rays + neutrons => Leakage current due to combined radiation

Working assumption:

additional current = (4) - (2) - (3) + (1)

Joachim Stroth

Hier sollten die bestrahlungsdosen angegeben werden. Auch details ueber die Bestrahlung!

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13Determination of the leakage currentDetermination of the leakage current

Bac

helo

r T

hesi

s S

arah

Ott

ersb

ach

-50 -40 -30 -20 -10 0 10 20 30

0,01

0,1

1

10

100L

ea

ka

ge

cu

rre

nt

[fA

]

Temperature [°C]

unirradiated component non-ionising component ionising component combined component

3T-Pixel/Mimosa19

Additional leakage current component identified for combined irradiation 27 % - 137% more than expected Combined radiation damage effects orders of magnitude higher than

single radiation are not found

27%

137%

Joachim Stroth

Was ist hier "expected". Hier sollten Angaben aus der Literatur kommen!Ist diese Ergebnis überraschend?

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14A short introduction into SB-PixelA short introduction into SB-Pixel

ResetTransistor

3T

Advantages: - no reset cycle/dead time necessary- Continuous read-out- usable as particle detector- leakage current compensation

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15

10

12

14

16

18

20

22

only neutron radiation additional 200kRad xray

No

ise

[e

]

T= - 20°C

Charge Collection Efficiency and Noise Charge Collection Efficiency and Noise

0,0

0,1

0,2

0,3

0,4

0,5

0,6

0,7

0,8

0,9

1,0

only neutron radiation additional 200kRad xray

Ch

arg

e C

oll

ec

tio

n E

ffic

ien

cy

T=-20°C

Decline of CCE, driven by non-ionizing radiationIncrease of (shot) noise driven by ionizing radiation

0 0.3 0.6 1.3 2.0

Radiation dose

0 0.3 0.6 1.3 2.0

Radiation dose

SB-Pixel/Mimosa18

Joachim Stroth

"Noise" sollte genauer spezifiziert sein!!

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16Fake Hit Rate and Random Telegraph SignalFake Hit Rate and Random Telegraph Signal

RTS is observed after irradiation with neutrons (non-ionizing radiation) Affected RTS pixels show excessive fake hit rates

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17

0,0 0,5 1,0 1,5 2,0

1E-9

1E-8

1E-7

1E-6

1E-5

1E-4

1E-3

0,01

fak

e h

it r

ate

radiation dose

SB -20°C SB 20°C 3T 20°C

Cooled irradiated SB-pixels show acceptable fake hit rate

Fake hit rate of 3T and SB-pixel at -20°C and 20°CFake hit rate of 3T and SB-pixel at -20°C and 20°Cfake hits / fram

e

400 k

40 k

4 k

0.4 k

…

Assume 400Mpixelin MVD

4 orders of magnitudeLower fake hit rate

Preliminary

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18Combined damage effects and fake hitsCombined damage effects and fake hits

Bac

helo

r T

hesi

s M

elis

sa D

omac

how

ski

0,0 0,5 1,0 1,5 2,0

1E-9

1E-8

1E-7

1E-6

1E-5

1E-4

1E-3

0,01

fak

e h

it r

ate

radiation dose

SB -20°C SB 20°C SB -20°C xray SB 20°C xrayC

BM

-Goa

l

fake hits / frame

400 k

40 k

4 k

0.4 k

…

• Fake hit rate seems dominated by ionizing dose• Reasonably low rate is reached after cooling• Expect better results in radiation hardened sensors

200 kRad ionizing radiation added to neutron irradiated sensors

Preliminary

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19SummarySummary

- Combined radiation damage effects in MAPS were evaluated for the first time.- Combined irradiated produces an additional leakage current- CCE degradation is driven by non-ionizing radiation while noise is increased

dominantly by ionizing radiation- Combined radiation damage effects orders of magnitude higher than single radiation

are not found- RTS can be an important source of fake hits- Cooled SB-pixels seem to be a good strategy to suppress fake hits- Increase of fake hit rate is mainly caused by ionizing radiation

Outlook- Annealing studies are under preparation- Irradiation with different neutron energies are planned- Tests with higher ionizing dose are proposed

Thank you for your attention

20

BackupBackup

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21

Limitation in the detection efficiency for SB-RTS-Limitation in the detection efficiency for SB-RTS-pixelspixels

10 20 30 40 50

1

2

3

4

IL

U2

I L

t

IC

ILU1

U2

I L

t

Constant threshold:=> Quantitative identification of RTS pixels is not reliable for SB-pixels=> Expect drop of identification efficiency with increasing leakage current

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22The measurement procedureThe measurement procedure

Lnon-irr. Lnonirr.+ionizing

Lnonirr.+non-ionizingLnonirr.+non-ionizing+ionizing

neutrons

xrays

xrays

- Feasibility to extract the leakage current contributions in detail- Feasibility to identify anomalous leakage current contribution due to combined irradiation

Leakage current measurements Lx

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23

50 100 150 200 250 300 350 400 450 500charge collectedADC

0.5

1

1.5

2

2.5

seirtne

nimargo

tsihmron

50 100 150 200 250 300 350 400 450 500


0.5

1

1.5

2

2.5

seirtne

nimargo

tsihmron

50 100 150 200 250 300 350 400 450 500

4 Pixel

1 Pixel

(EpiHit)

(DiodeHit)

Fe-SpectrumFe-Spectrum

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24

50 100 150 200 250 300 350 400 450 500 550 600 650 700 750charge collectedADC

0.5

1

1.5

2

2.5

seirtne

nimarg

otsihmron

50 100 150 200 250 300 350 400 450 500 550 600 650 700


0.5

1

1.5

2

2.5

seirtne

nimarg

otsihmron

50 100 150 200 250 300 350 400 450 500 550 600 650 700

Cd-SpectrumCd-Spectrum

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25Comparison Fe and CdComparison Fe and Cd


0.5

1

1.5

2

2.5

seirtneni

margotsihmron

50 100 150 200 250 300 350 400 450 500


0.5

1

1.5

2

2.5

seirtneni

margotsihmron

50 100 150 200 250 300 350 400 450 500


0.5

1

1.5

2

2.5

seirtne

ni

margotsihmron

50 100 150 200 250 300 350 400 450 500 550 600 650 700


0.5

1

1.5

2

2.5

seirtne

ni

margotsihmron

50 100 150 200 250 300 350 400 450 500 550 600 650 700

Three times as many electrons

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26Tolerance against non-ionizingg radiationTolerance against non-ionizingg radiation+3.3V

Output

SiO2 SiO2

N++

N+SiO2 SiO2

P++ P++ P++

GND GND

+3.3V

Bulk damage

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27

Tolerance against non-ionizing radiationTolerance against non-ionizing radiation+3.3V

Output

SiO2 SiO2

N++

N+SiO2 SiO2

P++ P++ P++

GND GND

+3.3V

Signal lost due to rekombination

Additional leakage current due to defects

Not movable

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28Radiation tolerance against ionizing radiationRadiation tolerance against ionizing radiation

Reset+3.3V+3.3V

Output

SiO2

N++ N++N+ P+

P-

P+

SiO2Positive Charge

Additional leakage by electrons from SiO2

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29Signal to Noise at T=-20°CSignal to Noise at T=-20°C

0 2 4 6 8 10

12

16

20

24

28

32

36

40

44

3T-Pixel Fe SB-Pixel Fe 3T Slow Fe 3T Cd

Sig

na

l to

No

ise

X Axis Title

0 0.3 0.6 1 2.0 0.6 1 200kRad200kRad

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30RTS of combined irradiated sensorsRTS of combined irradiated sensors

Unexpected: RTS-amplitude goes down by 47 ADC after irradiation with ionizing dose

0 2000 4000 6000 8000 10000Time@framesD10k=10Min

300

400

500

600

700

SDClangiS@CDAD

Xray + neutrons

Only neutrons

Same

pixel

Peak not discussed here

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31RTS in SB-pixel RTS in SB-pixel

The pixel output (CDS) show only a few fake hits, which coincide with the RTS driven change in the absolute potential (F1)

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32Fake hit rate of 3T and SB-pixel at 0°C and 20°CFake hit rate of 3T and SB-pixel at 0°C and 20°C

Cooled SB-pixels show a satisfactory low fake hit rate

Assuming 400 Million pixel:400 000 fake hit per frame expected

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33

0,0 0,5 1,0 1,5 2,0

1E-9

1E-8

1E-7

1E-6

1E-5

1E-4

1E-3

0,01

fak

e h

it r

ate

radiation dose

SB 0°C SB 20°C 3T 20°C

Fake hit rate of 3T and SB-pixel at 0°C and 20°CFake hit rate of 3T and SB-pixel at 0°C and 20°C

Cooled SB-pixels show a satisfactory low fake hit rate

Assuming 400 Million pixel:400 000 fake hit per frame expected

CB

M-G

oal

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34

0,0 0,5 1,0 1,5 2,0

1E-9

1E-8

1E-7

1E-6

1E-5

1E-4

1E-3

0,01

fak

e h

it r

ate

radiation dose

SB 0°C SB 20°C 3T 20°C

Adding 200kRad ionizing radiation…Adding 200kRad ionizing radiation…

Bac

helo

r T

hesi

s M

elis

sa D

omac

how

ski

Fake hit rate is dominated by ionizing radiation

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35

Sensors with improved charge collection Sensors with improved charge collection efficiencyefficiency

How to escapehere?

Bigger collection diodes may improve CCE => Tested with Mi-19

Diode 1 Diode 2

The radiation hardness of MAPS is improved by fast charge collection

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36Tolerance against non-ionizing radiationTolerance against non-ionizing radiation

Mi-9

Mi-9

Mi-15

Mi-18

Mi-1

9

Mi-18: 4 x 256 x 256 Pixels, standard diode (3 x 4 µm)Mi-19: 2 x 192 x 192 Pixels, L-shaped diode

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37ResultsResults

A. Büdenbender, Bachelor Thesis

Charge collection efficiency is indeed substantially increased

But the bigger collection diodes generate more noise

T= -20 °C

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38S/N of the sensorsS/N of the sensors

A. B

üden

bend

er, B

ache

lor

The

sis

Both MIMOSA-18 and MIMOSA-19 seem fairly radiation hardBig diodes have no advantages because of high noise

Insufficient S/N

Use beam test results fornon-irradiated chips.

Add information on CCE from Fe-55 tests.

Normalize collected charge according to CCE

Checked against beam test data with Mi15

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39ResultsResults

A. Büdenbender, Bachelor Thesis

Mi18 looses its advantage in noise after ~1013 neq/cm²

T= +20 °C

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40S/N of the sensorsS/N of the sensors

A. B

üden

bend

er, B

ache

lor

The

sis

At +20°C, the radiation hardness of Mi18 and Mi19 seems similar

Insufficient S/N

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41Leakage Current of Mimosa19, Diode 1Leakage Current of Mimosa19, Diode 1

0,0 5,0x1012 1,0x1013 1,5x1013 2,0x1013

0

10

20

30

40

50

60

70 T = 20°C T = -20°C

Leak

age

Cur

rent

[ fA

]

Radiation Dose [n/cm²]

The increase of leakage currents is not negligable

A. B

üden

bend

er, B

ache

lor

The

sis

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42CCE of Mimosa19, Diode 1CCE of Mimosa19, Diode 1

0,0 5,0x1012 1,0x1013 1,5x1013 2,0x10130,0

0,1

0,2

0,3

0,4

0,5

0,6

0,7

0,8

0,9

1,0

T = 20°C T = -20°C

Cha

rge

Col

lect

ion

Effi

cien

cy (

4 pi

xel)

%


The CCE depends on the temperature

A. B

üden

bend

er, B

ache

lor

The

sis

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43

The Munich – Ljubljana puzzle

We irradiated at the FRM-II reactor in Munich

We irradiated at the Ljubljana triga reactor

So what?

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44CCE of Mimosa18 Munich - LjubljanaCCE of Mimosa18 Munich - Ljubljana

0,0 4,0x1012 8,0x1012 1,2x1013 1,6x1013 2,0x10130,0

0,1

0,2

0,3

0,4

0,5

0,6

0,7

0,8

Munich, T = 20°C Munich, T = -20°C Ljubljana, T = 20°C Ljubljana, T = -20°CC

harg

e C

olle

ctio

n E

ffici

ency


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45CCE of Mimosa18 Munich - LjubljanaCCE of Mimosa18 Munich - Ljubljana

0,0 4,0x1012 8,0x1012 1,2x1013 1,6x1013 2,0x10130,0

0,1

0,2

0,3

0,4

0,5

0,6

0,7

0,8

Munich, T = 20°C Munich, T = -20°C Ljubljana, T = 20°C Ljubljana, T = -20°CC

harg

e C

olle

ctio

n E

ffici

ency


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46Noise of MIMOSA-18, Munich - LjubljanaNoise of MIMOSA-18, Munich - Ljubljana

0,0 5,0x1012 1,0x1013 1,5x1013 2,0x10130

5

10

15

20

25

30

35

40

45

50

55

Munich, T = 20°C Munich, T = -20°C Ljubljana, T = 20°C Ljubljana, T = -20°CN

oise

[ e_ ]


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47Signal over Noise of Mimosa18Signal over Noise of Mimosa18

0,0 5,0x1012 1,0x1013 1,5x1013 2,0x10130

5

10

15

20

25

30

35

40

45E

xpec

ted

S/N

(4

pixe

ls)

Neutron Fluence [neq

/cm²]

Munich Ljubljana

Insufficient S/N

Lines to guide the eyes

T=-20°C

Ljubljana neutrons seem roughly a factor 2 more damagingthan Munich neutrons. Why?

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48

What means 10What means 101313 n neqeq/cm²? My current /cm²? My current

understandingunderstanding

1,1

Ljubljana ~0.9e13n~0.9e13n~1.8e13n

25%75%

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49

What means 10What means 101313 n neqeq/cm²? My current /cm²? My current

understandingunderstanding

1,0

Munich ~0.97e13~0.03e13

NIEL of both sources should be equal.

But Ljubljana applies four times more neutrons.

Mismatch could be caused by overlooked effectof slow neutrons. Neutron capture in boron doping?

97%3%

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50What means neutron capturingWhat means neutron capturing

slow n + 10B

Alpha

6Li

+2.31 MeV

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51Temperature effects on RTSTemperature effects on RTS

Hopkins et al.: Period and amplitude of RTS increases with temperature

Output signal of a selected MAPS pixel showing RTS

If RTS amplitude < threshold => no fake hitsHypothesis: Cooling => less RTS-Pixels? D

. Doe

ring

, Bac

helo

r T

hesi

s

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52RTS-pixels: How to identifyRTS-pixels: How to identifyt [a.u.]

UC

DS

Unambiguous RTS-pixel

1) Find the baseline of the pixel signal

2) Define a threshold

3) Scan output for segments of data above this threshold

4) If segment is found => RTS-pixel

D. D

oeri

ng, B

ache

lor

The

sis

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53

RTS-pixels: Parameters in the identification RTS-pixels: Parameters in the identification algorithmalgorithm t [a.u.]

UC

DS

Ambiguous RTS-pixel

Some pixels show a“maybe RTS with smallamplitude”. Choose good threshold

UC

DS

t [a.u.]This is not an RTS-pixel

Some pixels show too fast RTS for being detected.Minimum time of RTS signature plays a role.

Same data!

D. D

oeri

ng, B

ache

lor

The

sis

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54

RTS-pixels: Parameters in the identification RTS-pixels: Parameters in the identification algorithmalgorithm t [a.u.]

UC

DS


RTS- pixels might be not recognized because of insufficientobservation time.

Observation time: 4.5 min

UC

DS

D. D

oeri

ng, B

ache

lor

The

sis

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55Detected RTS-pixels over timeDetected RTS-pixels over time

Saturation value

Results presented today: ~ 5 min

Speculation:Are there two kinds of origins of RTS having different time constant?

D. D

oeri

ng, B

ache

lor

The

sis

/19




56RTS-pixels: How to identifyRTS-pixels: How to identifyt [a.u.]

UC

DS


1) Find the baseline of the pixel signal

2) Define a threshold:

3) Scan output for segments of data above this threshold

4) If segment is found => RTS-pixel

150 electrons reasonable threshold for detector operation

Segments of dt > 0.5 s are identified D. D

oeri

ng, B

ache

lor

The

sis

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57Identified RTS - pixels as function of temperatureIdentified RTS - pixels as function of temperature

Number of identified RTS - pixels is dramatically reduced by cooling

RTS pixel if signature with:

•Amplitude >150e ENC •Tmin = ~ 0.5s•Tmax= ~ 45 min

Preliminary

0,0 5,0x1012 1,0x1013 1,5x1013 2,0x1013

0,1

1

10

RT

S-P

ixel

s [%

]

Radiation dose

-20°C 0°C 20°C 40°C

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58

Chips with intrinsic leakage current compensation Chips with intrinsic leakage current compensation (SB-pixel)(SB-pixel)

IC

IL U1

U2

vdd (+3.3V)

IL

t

UCDS

t

IC, U2

t

RTS should only be visible in UCDS, if new equilibrium is being establishedSteps should be visible in U2

(Output)

Threshold

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59Spatial distribution of fake hitsSpatial distribution of fake hits

PixelNr

Pix

elN

r

low

medium

high

Fake hit rate

T=40°C

Run 18040FakeHitRateMimosa.nb

Fake hits are caused by randomly distributed hot pixels

D. D

oeri

ng, B

ache

lor

The

sis

Documents

Radiation hardness studies with combined irradiated MAPS