Aging Studies On Layer 00

Italian Summer Internship Report

Sept,23th 2011

Luca Somaschini Università degli Studi di Milano

Silicon Detectors

DEPLETION VOLTAGE:

The external voltage

(BIAS) required to extend the Electric

field across the whole bulk (i.e. to collect all the charges produced by ionizing particles)

9/23/11 Luca Somaschini 2  

Radiation Damages

BULK DAMAGES: Besides

ionization, Hadrons can

DISPLACE lattice atoms;

9/23/11

Interstitial and vacancy defect creation.

exiting particle

incident particle

interstitial vacancy

Frenkel pair

OVERALL EFFECT: changes in the depletion voltage

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Evolution of Dep. Volt.

9/23/11 Luca Somaschini 4  

Signal Bias Scan

Procedure to measure the silicon sensor depletion voltage Fit => Depletion voltage: 95% of charge is collected

9/23/11

Bias voltage (V)0 20 40 60 80 100 120 140 160 180 200

Clu

ster

Cha

rge

(AD

C c

ount

s)

0

5

10

15

20

25

30

35

40

effic

ienc

y

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1Fit Parameters 0.735± p0 = 19.647

0.004± p1 = 0.061 1.229± p2 = 48.898 2.686± p3 = 91.203

Extremal Charges 0.19±Charge Max = 28.01 0.19±Charge Min = 10.70

Ladder: f843_0

Luca Somaschini 5  

Radiation Dose

9/23/11

What is the relation between Absorbed Dose and Delivered

Luminosity?

If |z| < 50 cm

Measured using 916 dosimeters placed in the detector

* Tesarek, R. J.; D'Auria, S.; Hocker, A.; Kordas, K.; McGimpsey, S.; Worm, S. NIM A 514 p. 188

Luca Somaschini 6  

Layer 00

9/23/11

We will restrict our analysis to Layer 00: • It’s the closest layer to the beampipe • It recieves highest radiation doses • The radiation dose received by L00 is sensitive to changes in beam position;

• Only good runs data will be considere; • Good Run List: goodrun_qcd_si.list

Luca Somaschini 7  

Layer 00

9/23/11

Y-Z PLANE

2 Barrels of three segment each 94 cm long

72 Ladders Wides: Hamamatsu - Narrows: SGS

Thompson - Narrows Oxygenated: Micron

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Layer 00

9/23/11

X-Y PLANE

•  6 Wedges •  12 Ladders

•  6 Wides •  6 Narrows

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Approximation 0

9/23/11

• All the ladders are in the same position

• The beam is in the center of the beam-pipe

1.62 cm

1.62 cmLUMINOSITY ó DOSE (i.e. no differences between a DepVolt vs

Luminosity plot and a DepVoltage vs Dose )

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9/23/11

Approximation 0

Luminosity (pb-1)0 2000 4000 6000 8000 10000 12000

Dep

Vol

tage

(V)

50

100

150

200

250

f843_0 / ndf 2r 17 / 25

Prob 0.8817p0 3.425± 26.86 p1 0.0006835± 0.01816

/ ndf 2r 17 / 25Prob 0.8817p0 3.425± 26.86 p1 0.0006835± 0.01816

f843_0

Good Fits: low chi-square per

degree of freedom

Luca Somaschini 11  

9/23/11

Approximation 0

Luminosity (pb-1)0 2000 4000 6000 8000 10000 12000

Dep

Vol

tage

(V)

50

100

150

200

250

300

f823_1 / ndf 2r 135.7 / 19

Prob 1.229e-19p0 4.893± 41.39 p1 0.0008957± 0.0181

/ ndf 2r 135.7 / 19Prob 1.229e-19p0 4.893± 41.39 p1 0.0008957± 0.0181

f823_1

Bad Fits: very high chi-

square per degree of freedom

Luca Somaschini 12  

9/23/11

ChiSquareEntries 72Mean 3.052RMS 1.83

0 2 4 6 8 100

5

10

15

20

25

ChiSquareEntries 72Mean 3.052RMS 1.83

ChiSquare

Radiation Dose

We will work only on ladders with chi-squre per deg. of

freedom <3;

Selection of: 42 of 72

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Luminosity (pb-1)0 2000 4000 6000 8000 10000

Dep

Vol

tage

(V)

50

100

150

200

250

All Together

Expected Corrections

9/23/11

Two different behavior before inversion point

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Approximation 1

9/23/11

• Wide and Narrow Ladders have different radii

• The beam is in the center of the beam-pipe

1.35 cm1.62 cm

Conversion of Scan Luminosity to dose

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Dose (Krad)0 1000 2000 3000 4000 5000 6000 7000 8000

Dep

Vol

tage

(V)

50

100

150

200

250

All Together

Expected Corrections

9/23/11

Still two different behavior before inversion point

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Narrow Ladders

9/23/11

0 2000 4000 6000 8000 10000

50

100

150

200

250

300

350

400

450

500

NARROWs

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Wide Ladders

9/23/11

Dose (Krad)0 1000 2000 3000 4000 5000 6000 7000 8000

Dep

Vol

tage

(V)

50

100

150

200

250

WIDEs

The observed split is due to Wides

behaving differently to Narrows

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Approximation 2

9/23/11

• Use the real position of the ladders

• Consider the real position of the beam

E!ec

tive

dist

ance

Changes in the beam-ladders distance means changes in the absorbed

dose Luca Somaschini 19  

Beam Position

9/23/11

The DepVoltage depends on the absorbed dose.

The absorbed dose depends on the beam position between two scans.

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Beam Position

9/23/11

Store Number1000 2000 3000 4000 5000 6000 7000 8000 9000

Y Be

am P

ositi

on (c

m)

0

0.1

0.2

0.3

0.4

0.5

0.6

Y Beam Position

Movement is about 0.5cm

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Beam Position

9/23/11

Store Number1000 2000 3000 4000 5000 6000 7000 8000 9000

Y Be

am P

ositi

on (c

m)

0

0.1

0.2

0.3

0.4

0.5

0.6

Y Beam Position

Simple Correction: divide into three

region with similar beam position

Luca Somaschini 22  

9/23/11

Store Number0 2000 4000 6000 8000

Y Be

am P

ositio

n

0

0.1

0.2

0.3

0.4

0.5

0.6

Y Beam Position

Store0 1000 2000 3000 4000 5000 6000 7000 8000 9000

)-1

Lum

inos

ity (

nb

0

2000

4000

6000

8000

10000

12000

Luminosity Per Store

Store0 1000 2000 3000 4000 5000 6000 7000 8000 9000

)-1

Tota

l Lum

inos

ity (p

b

0

2000

4000

6000

8000

10000

12000

LuminosityLuminosity

Large beam offset had negligible contribution

Luca Somaschini 23  

9/23/11

Plot @ a fixed dose of 6000 krad;

Phi Dependence

The Phi dependence is smaller after the correction. Note the difference of Chi-Square per deg. of freedom

/ ndf 2r 197 / 11p0 0.9± 141.4

)° (q-150 -100 -50 0 50 100 150

Dep

Vol

tage

(V)

0

20

40

60

80

100

120

140

160

180

/ ndf 2r 197 / 11p0 0.9± 141.4

/ ndf 2r 197 / 11p0 0.9± 141.4

Per Wedge Gruping

/ ndf 2r 49.41 / 11p0 0.9± 143.4

()q-150 -100 -50 0 50 100 150

Dep

Vol

tage

(V)

0

20

40

60

80

100

120

140

160

/ ndf 2r 49.41 / 11p0 0.9± 143.4

/ ndf 2r 49.41 / 11p0 0.9± 143.4

Per Wedge Grouping

Luca Somaschini 24  

Dose (Krad)0 1000 2000 3000 4000 5000 6000 7000 8000

Dep

Volta

ge (V

)

40

60

80

100

120

140

160

180

200

220

All Together

Results

9/23/11

Reduction of point spread at low luminosity; no effect at high luminosities.

Luca Somaschini 25  

Results

9/23/11

Dose (Krad)0 1000 2000 3000 4000 5000 6000 7000 8000

Dep

Vol

tage

(V)

40

60

80

100

120

140

160

180

200

220

All Together

Dose (Krad)0 1000 2000 3000 4000 5000 6000 7000 8000

Dep

Vol

tage

(V)

40

60

80

100

120

140

160

180

200

220

All Together

Non Corrected – Corrected

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Results

9/23/11

The increase of integrated luminosity has a larger effect compared to changes of beam

position

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Manufacturer

9/23/11

An important difference appears in the behaviour of ladders of different

manufacturer

Luca Somaschini 28  

Dose (Krad)0 2000 4000 6000 8000 10000 12000

Dep

Volta

ge (V

)

0

50

100

150

200

250

300

SGS Thompson- Hamamatsu - MicronSGS Thompson- Hamamatsu - Micron

Manufacturer

9/23/11

Hamamatsu (Wide) SGS Thompson (Narrow)

Micron (Narrow Oxygenated)

Beam Position Corrected

Luca Somaschini 29  

Manufacturer

9/23/11

Oxygenated ladders: •  Inversion point at higer dose

•  Smaller slope •  Live ≈ twice as long as Hamamatsu

SLOPES (10-2 V/KRad):

Hamamatsu: 2.49 ± 0.01 SGS – Thompson: 1.78 ± 0.01

Micron (Oxygenated): 1.366 ± 0.006

Oxygenateds have a longer life!! Luca Somaschini 30  

Conclusions

9/23/11

•  BeamLine – Detector distance, for aging effects, is relevant only at low doses

•  At higher doses the trend is driven by luminosity

•  X-Y Slope and beam width are not relevant •  Great differences come from manufacturers •  Oxygenated ladders introduce great

improvements

Luca Somaschini 31  

Further Investigations

9/23/11

•  Influence of dose derived from beam losses and quenches

•  Influence of temperature changes

Luca Somaschini 32  

Thanks to

Mentor: Ankush Mitra

Institute of Physics - Academia Sinica

Supervisor: Benedetto Di Ruzza

FNAL

Thanks to

Fermilab Staff for the opportunity of

this summer

Back Up

9/23/11 Luca Somaschini 35  

Silicon Detectors Particles traveling through a silicon

sensor can produce free charges.

P-N Junction creates an electric field

depleted from free charges.

Charges can be collected thanks to the

electric field. 9/23/11

Cathode

Luca Somaschini 36  

Silicon Detectors Without bias voltage only charges in dep. region are collected.

An Extenal Potential (BIAS) is applied to

extend this region into the bulk.

The higher voltage is the wider electric field

is. 9/23/11 Luca Somaschini 37  

Radiation Damages

HAMBURG MODEL: complex THE OVERALL EFFECT: changes in the depletion voltage

REMEMBER THAT: Radiation affects all

devices (detectors, chips …)

*Jeffery Wyss – Exposure to radiation damage: concepts, quantities, environments - http://agenda.infn.it/conferenceTimeTable.py?confId=3245

9/23/11 Luca Somaschini 38  

Signal Bias Scan

WHAT: Procedure to measure the silicon sensor depletion voltage;

WHEN: at CDF is performed about every 6

months;

HOW: measure the collected chage at different bias voltages

9/23/11 Luca Somaschini 39  

Signal Bias Scan

This gives one couple of values: DEPLETION VOLTAGE vs DELIVERED LUMINOSITY

For: •  Each Ladder •  Each Bias scan

9/23/11 Luca Somaschini 40  

Bias Scan Each Landau X Gauss Gives a point at a

different voltage;

9/23/11

Bias voltage (V)0 20 40 60 80 100 120 140 160 180 200

Clu

ster

Cha

rge

(AD

C c

ount

s)

0

5

10

15

20

25

30

35

40

effic

ienc

y

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1Fit Parameters 0.735± p0 = 19.647

0.004± p1 = 0.061 1.229± p2 = 48.898 2.686± p3 = 91.203

Extremal Charges 0.19±Charge Max = 28.01 0.19±Charge Min = 10.70

Ladder: f843_0

Luca Somaschini 41  

Dose Mapping

Distributio of Dose obtained

with 916 dosimeters

http://cdf-radmon.fnal.gov/

public/plots

9/23/11 Luca Somaschini 42  

Dosimeters Mapping

9/23/11

Dispalcement of the 916

dosimeters

Luca Somaschini 43  

Expected Corrections

9/23/11

Some error bars don’t cross the fitted line.

Is that systematics or is it caused by

our approximation?

Luca Somaschini 44  

Expected Corrections

9/23/11 Luminosity (pb-1)

0 2000 4000 6000 8000 10000 12000

Dep

Vol

tage

(V)

50

100

150

200

250

f843_0 / ndf 2r 17 / 25

Prob 0.8817p0 3.425± 26.86 p1 0.0006835± 0.01816

/ ndf 2r 17 / 25Prob 0.8817p0 3.425± 26.86 p1 0.0006835± 0.01816

f843_0

Luca Somaschini 45  

Luminosity (pb-1)0 2000 4000 6000 8000 10000

Dep

Vol

tage

(V)

50

100

150

200

250

All Together

Expected Corrections

9/23/11

Each ladder has a different behavior

Luca Somaschini 46  

Expected Corrections

9/23/11

Luminosity (pb-1)0 2000 4000 6000 8000 10000 12000

Dep

Vol

tage

(V)

50

100

150

200

250

f843_0 / ndf 2r 17 / 25

Prob 0.8817p0 3.425± 26.86 p1 0.0006835± 0.01816

/ ndf 2r 17 / 25Prob 0.8817p0 3.425± 26.86 p1 0.0006835± 0.01816

f843_0

Different Ladders fits have different slopes

Luca Somaschini 47  

Expected Corrections

9/23/11

Luminosity (pb-1)0 2000 4000 6000 8000 10000 12000

Dep

Vol

tage

(V)

50

100

150

200

250

f843_0 / ndf 2r 17 / 25

Prob 0.8817p0 3.425± 26.86 p1 0.0006835± 0.01816

/ ndf 2r 17 / 25Prob 0.8817p0 3.425± 26.86 p1 0.0006835± 0.01816

f843_0

Different Ladders fits could overlap

after the correction for the beam

position

Luca Somaschini 48  

Expected Corrections

9/23/11

Let’s check by starting to take into account some details, if we can, to

improve our fits.

Luca Somaschini 49  

Beam Position

9/23/11

X Beam Position (cm)-0.4 -0.35 -0.3 -0.25 -0.2 -0.15 -0.1 -0.05

Y Be

am P

ositi

on (c

m)

0

0.1

0.2

0.3

0.4

0.5

0.6

XY Beam PositionBeam Position

for all RunII stores

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Beam Position

9/23/11

Store Number1000 2000 3000 4000 5000 6000 7000 8000 9000

X Be

am P

ositi

on (c

m)

-0.4

-0.35

-0.3

-0.25

-0.2

-0.15

-0.1

-0.05

X Beam Position

Movement is about 0.1 cm

Luca Somaschini 51  

()q-150 -100 -50 0 50 100 150

Dep

Volta

ge (V

)

0

20

40

60

80

100

120

140

160

Per Wedge GroupingPer Wedge Grouping

9/23/11

Plot @ a fixed dose of 6000 krad;

With Correction Without Correction

Phi Dependence

Luca Somaschini 52  

Z (cm)-50 -40 -30 -20 -10 0 10 20 30 40 50

Dep

Volta

ge (V

)

0

20

40

60

80

100

120

140

160

Per Barrel Grouping - AllPer Barrel Grouping - All

9/23/11

Plot @ a fixed dose of 6000 krad;

With Correction Without Correction

Z Dependence

The z dependence is present but is small

Luca Somaschini 53  

Z (cm)-50 -40 -30 -20 -10 0 10 20 30 40 50

Dep

Vol

tage

(V)

0

20

40

60

80

100

120

140

160

Per Barrel Grouping - AllPer Barrel Grouping - All

9/23/11

Plot @ a fixed dose of 6000 krad;

With Correction Without Correction

Z Dependence

Luca Somaschini 54  

Z (cm)-50 -40 -30 -20 -10 0 10 20 30 40 50

Dep

Volta

ge (V

)

0

20

40

60

80

100

120

140

160

Per Barrel Grouping - AllPer Barrel Grouping - All

9/23/11

Plot @ a fixed dose of 6000 krad;

Z Dependence

Asymmetry: maybe influence of z beam

position

Luca Somaschini 55  

Store Number1000 2000 3000 4000 5000 6000 7000 8000 9000

Z Be

am P

ositi

on (c

m)

-15

-10

-5

0

5

10

15

Z Beam Position

Beam Position

9/23/11

It would require an extra investigstion

Luca Somaschini 56  

Other Corrections

9/23/11

Store Number0 1000 2000 3000 4000 5000

X Be

am W

itdh

(cm)

0

0.0005

0.001

0.0015

0.002

0.0025

0.003

0.0035

0.004

X Beam WidthX Beam WidthX BEAM WIDTH

IRRELEVANT: 2 order of magnitude smaller than

position effects

Luca Somaschini 57  

Other Corrections

9/23/11

Store Number0 1000 2000 3000 4000 5000

Y Be

am P

ositio

n (c

m)

0

0.0005

0.001

0.0015

0.002

0.0025

0.003

0.0035

0.004Y Beam WidthY Beam WidthY BEAM WIDTH

IRRELEVANT: 2 order of magnitude smaller than

position effects

Luca Somaschini 58  

Other Corrections

9/23/11

Store Number0 2000 4000 6000 8000

X Be

am S

lope (

mili-r

ad)

0.0002

0.0003

0.0004

0.0005

0.0006

0.0007

0.0008

0.0009

0.001

X Beam SlopeX Beam SlopeX BEAM SLOPE

Luca Somaschini 59  

Other Corrections

9/23/11

Store Number0 2000 4000 6000 8000

Y Be

am S

lope

(mili-

rad)

-0.3

-0.2

-0.1

0

0.1

0.2

0.3

0.4

-310×

Y Beam SlopeY Beam SlopeY BEAM SLOPE

Luca Somaschini 60  

Slope to Distance

9/23/11

   

R = tan(slope) * 94 cm ≈ 0.4 – 1 micron

IRRELEVANT: 3 order of magnitude smaller than

position effects

R

Luca Somaschini 61  

9/23/11

CDF Overview

Luca Somaschini 62  

9/23/11

CDF Overview

Luca Somaschini 63  

9/23/11

CDF Silicon Overview

Luca Somaschini 64  

9/23/11

Dose vs Radius

Evolution of equivalent dose with

distance from the beam

Luca Somaschini 65  

9/23/11

Dose vs Radius

Official CDFII plot.

Dep Voltage vs Luminosity.

NO

CORRECTIONS

Luca Somaschini 66