A comparative study of mixed irradiated silicon strip sensors

KIT – University of the State of Baden-Wuerttemberg and National Research Center of the Helmholtz Association

Institut für Experimentelle Kernphysik

www.kit.edu

A comparative study of mixed irradiated silicon strip sensors19th RD50 Workshop 21.11. – 23.11.2011

Florian Petry, Robert EberT. Barvich, F. Bögelspacher, W. de Boer, A. Dierlamm, A. Kornmayer, Th. Müller, P. Steck

19th RD50 Workshop221.-23.11.2011

Robert EberInstitut für Experimentelle Kernphysik, KIT

Ingredients for the study

Introduction

Sensors

Mixed irradiation scheme

Annealing procedure

ALiBaVa measuremets

Results

Charge collection

Signal to noise ratio

Leakage current

Summary

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Sensor overview

Sensor thickness: 300µm

5 sensors of each material

Material Type Pitch (µm) Manufacturer

FZ p-in-n 50 (5) HIP

FZ n-in-p (p-spray) 80 (5) Micron

MCz p-in-n 50 (5) HIP

MCz n-in-p (p-spray) 50(1), 80(3), 100(1) Micron

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Irradiation

Mixed irradiation with protons and neutrons

Chose 5 fluence mixtures corresponding to 5 different radii in the CMS Tracker after 3000fb-1

Irradiation with Protons in Karlsuhe

ZAG: Cyclotron, 23MeV protons

Irradiation with neutrons in Louvain-la-Neuve

Neutron generation by shooting deuterons on Be target

1 step only neutron irradiation

Radius (cm)

Total fluence (neq/cm2)

Neutron(neq/cm2)

Proton(neq/cm2)

5 1.2*1016 10.0*1014 110*1014

20 1.8*1015 5.5*1014 12.5*1014

60 7.3*1014 4.5*1014 2.8*1014

120 4.6*1014 3.8*1014 0.8*1014

>120 4.0*1014 4.0*1014 -

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Annealing

Logarithmic annealing steps to observe

short term (beneficial) annealing

long term (reverse) annealing

Temperature (°C)

Duration (min)

Sum @RT Annealing (d)

60 20 4

60 20 8

60 40 15

60 76 28

80 15 58

80 30 133

80 60 337

M.Moll, phd thesis, Hamburg, 1999

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Parameterisation of charge collection

Beneficial annealing Reverse annealing Stable damage

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Measurement

Measurement Setup: 2 ALiBaVa stations in Karlsruhe90Sr source

Signal

Signal to noise ratio

Leakage current

Temperature: -20°C (-30°C)

Voltage 0V – 1000V

Cuts

Seed: S/N > 5

Neighbour: S/N > 2

Total error on measurements: 2.5%

Error on irradiated fluence > 10%

The small ALiBaVa station

HVPre-cooling

DB

Scintillator

Sensor

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Measurement Results

Parameters

T = -20°CV = 900V

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Charge collection

P-type materials collect more charge than n-type materials

FZ-n

shows highest dependence on annealing time

Large drop in charge collection after 10d@RT (reverse annealing)

Only small dependence of charge collection on annealing time for other materials

P

N

P

N

Incr

easi

ng f

luen

ce

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Charge collection

1.8*1015neq/cm2

FZ-p shows largest charge collection

Charge multiplication for large annealing (charge > 24000 e-)

MCz: almost no dependence on annealing time

1.2*1016neq/cm2

FZ-n: No signal at highest fluence for all annealing steps

FZ-p: rise in signal for long annealing time

MCz-p sensor didn‘t work for first annealing step

MCz-n: no signal at T= -20°C

Incr

easi

ng f

luen

ce

MCz-nT= -30°C

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Charge Collection overview

Max: 24k

Max: 22k

Max: 15k/40k

Max: 10k

MCz-nT=-30°C

No Signal at T=-20°C

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Signal to Noise

P

N

4. Lower limit, seed cut > 52. Same rangeFZ-n drops out

1. All quite good 3. p is better than n

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Charge multiplication

Signal increases after Annealing of >100d@RT

Signal to noise ratio doesn‘t decrease

Large increase of leakage current

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Charge collection / multiplication

Landau-Gauß-Fit broadens very much

Peak is shifted to higher values

Not a MIP signal any more

usual distribution

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Charge collection / multiplication

MPV cannot be determined very well

MCz-nT=-30°C

FZ-p + MCz-pT=-20°C

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Charge Collection / Signal to Noise Summary

CC

S/N

T= -30°CMCz-n


15d 337d

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Leakage Current Summary


15d 337d

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Neutron only / mixed irradiation

Mixed irradiation F = 4.6*1014neq/cm2

F(p) = 0.8*1014neq/cm2

F(n) = 3.8*1014neq/cm2

Neutron only irradiation

F(n) = 4.0*1014neq/cm2

1. Neutron only irradiation: • FZ-n has smaller signal than

MCz-nsimulated by M. Huhtinen NIMA 491, 194-215, 2002

2. Mixed irradiation:• No improvement in CC due to

mixed irradiationG. Casse et al. Vertex2008:036, 2008

MCz

FZ

N-type

19th RD50 Workshop1921.-23.11.2011


Summary

P-type materials showed higher charge collection and signal to noise

FZ-p performance most interesting

Charge multiplication only seen with FZ-p F > 1*1015neq/cm2, A > 100d@RTManufacturer Micron

Highest leakage current

FZ-n showed largest dependence on annealing time

Not usable at high fluences

Charge collection of MCz materials does not anneal very much

MCz-n is not working at T= -20°C at F=1.2*1016neq/cm2

Additional differences between n-type and p-type materials due to manufacturer?

Compare to other studies: Charge multiplication study, HPK

19th RD50 Workshop2021.-23.11.2011


Thanks for your attention

Diploma thesis of F. Petry (IEKP-KA/2011-27)

Will be published soon:

http://www-ekp.physik.uni-karlsruhe.de/pub/web/thesis/iekp-ka2011-27.pdf



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