synchrotron and pion beam tests of 3d medipix2 and timepix detectors r. bates a, k. c. akiba h, l....

Synchrotron and pion beam tests of 3D Medipix2 and TimePix Detectors

R. Batesa, K. C. Akibah, L. Alianellib, M. Artusoj, F. Bayer, J. Buytaerte, P. Collinsd, M. Crossleye, L. Eklunda, C. Fletac, A. Gallase, M. Gandelmani, M. Gersabecka , E.N. Gimenezb, V. Gligorova, T. Husef, M. Johng, L. F. Llina, M. Lozanoc, Aaron Mac Raighnea, D. Maneuskia, J. Marchalb, T. Michelk, M. Nicola, G. Pellegrinic, D. E. Perirae, R. Plackettd, V .O'Sheaa, C. Parkesa, E. Rodriguesa, K.J.S. Sawhneyb, N. Tartonib, P. Vazqueze.

a) University of Glasgow, Department of Physics and Astronomy, Glasgow, UK.b) Diamond Light Source Ltd, Oxfordshire, UK.c) Instituto de Microelectronica de Barcelona, IMB-CNM-CSIC, Barcelona, Spain.d) CERN CH-1211, Genève 23, Switzerland. e) Facultad de Fisica , University of Santiago de Compostela, Santiago de Compostela, Spain.f) Department of Physics, The University of Liverpool, Liverpool, United Kingdom. g) Department of Physics, University of Oxford, UK.h) Nikhef, Science Park 105, 1098 XG Amsterdam, The Netherlands.i) Instituto de Fisica, Univ. Federal do Rio de Janeiro, Brazil.j) Syracuse University, Syracuse, NY 13244, U.S.A.k) Erlangen Centre for Astroparticle Physics, Universität Erlangen-Nürnberg, Erwin-Rommel-Str. 1, 91058 Erlangen, Germany

Richard Bates, RD50, Nov 2009 2

Outline

• Introduction– 3D double sided detectors substrates– Medipix / Timepix description

• Micro-focussed X-ray beam– Set-up– Background subtraction– Efficiency and Charge Sharing

• Pion-beam from SPS– Set-up– Efficiency and Charge Sharing

• Conclusions


Detector substrates3D and Planar

• Detectors are fabricated at Centro Nacional de Microelectronica, Barcelona

• Columns are etched from opposite sides of substrate• Column fabrication

» Reactive ion etching

» Partial filing with polysilicon then doping

Radiation Hardness

Reduced Charge Sharing

Charge sharing in double-sided 3D Medipix2 detectors

D. Pennicard, et al. ,NIM A, Vol. 604, Issues 1-2, 1 June 2009, Pages 412-415

Medipix unit cell55µm on the sideMaximum drift length is 38.9µm


Medipix and Timepix

• 65k single-photon counting pixel array

• Square pixel size of 55µm

• Electron or hole collection

• Threshold equalisation

• Count rate of ~100kHz

• Readout in 300µs

• High dynamic range

Amplifier

Discriminator

Pixel Counter

Readout

+1

Threshold

Detector substrate

Amplifier

Discriminator

Pixel Counter

Readout

Threshold

N counts

+N

MedipixTimepix


X-ray Beamline Set-up

• B16 Test beamline at the Diamond

• Monochromatic X-ray beam of 14.5keV

• Beam size FWHM were measured as

– 4.5±0.3 µm in x

– 6.7±0.3 µm in y

• Six degrees of freedom, 0.1µm translational and 5µrad rotational

• Alignment of 0.3o in x and 0.9o in y

Compound refractive lens

Beam

Beam 3D detector

Detector substrate raster scanned relative to the beam


Pixel Maps

• 77.5µm square scans (55µm pixel)

• 2.5µm steps

• Background subtracted

• Interpolated

• THL ~ 50% of beam energy

N-Type

0.2

0.4

0.6

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P-Type

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1Planar

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Cross sectionFitted functionBackground with central pixel

Background Subtraction

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1. Build up scan

2. Remove central pixel/ micro-focused beam.

3. Perform cross sections to estimate background in central pixel

4. Perform surface fit

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Detection Efficiencies

55µmNormalisation

Inefficiencies Centre Corners*

Planar 0% 7%

3D N –Type 3% 7%

3D P –Type 4% 7%

*efficiencies at the corners due to electrodes structures and charge sharing

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Central electrode

55µm


Charge Sharing

4 6 8 10 12 14 16 18 20 22 240.95

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Line Sections

THL level

~50% beam energy

THL level

~25% beam energy

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1.6Cross section at Pixel Boundary

THL~25%

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P-Type

42.5µm

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THL~25%

THL~50%THL~75%

P-Type


Charge Sharing

0 5 100.4

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THL~25%

THL~50%THL~75%

N-Type

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THL~50%THL~75%

Planar

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THL~50%THL~75%

P-Type

5 10 15

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P-Type

5 10 15

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THL~25%

THL~50%THL~75%

N-Type

5 10 15

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To

p q

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of p

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s n

ea

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THL~25%

THL~50%

THL~75%

Planar

THL~25%

THL~50%

THL~75%

P-Type N-Type Planar

µm µm µm

No

rma

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co

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Reduced level of over counting and under counting in 3D

= Reduced Charge Sharing

Note : at 14.5keV – gets worse for thicker Silicon & higher energy X-rays in Planar device

FWHM

Planar: ~12µm

3D: ~8µm

Double counting

Planar: 0.5 photons

3D: 0.25 photons


MIP beam from SPS

• Secondary 120 GeV pion beam from SPS• 4 Timepix, 2 Medipix planes in telescope• DUT: double sided 3D N-type sensor from

CNM/Glasgow• Expected track extrapolation error: < 3 μm

Pion beamIndividual pion tracks

Medipix & LHCb

telescope DUT


Cluster width

• Fit to determine perpendicular position:-0.32 degrees

• Flat distribution in y• Ratio ~1 at perpendicular

12


Detection Efficiency.Medipix Mode(counts above threshold)

• Averaged result over all pixels

• Drop in efficiency at the electrode positions

• Here: efficient if hit in 3x3 pixel array around intercept point

• MIPs give a much higher efficiency than with x-rays due to track nature of charge deposition

Absolute efficiencies

50

60

70

80

90

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Centre Corner

Inefficiencies 0.5% 5%

Threshold just above noise level


Energy Spectra TOT Mode

ADC hit in pixel ADC hit in 3x3 pixel

average ADCvs

(x,y)

50

60

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60

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•Same picture as before:Two column types have different signal size


Landaus as function of radius

• ADC counts (ToT) as function of distance from centre of cell

15


More landaus

• Just 1D plots of the columns of the plot on the previous slide

• Basically 2 Landaus:MPVs are ~7 and ~30

• Now for some explanation...

centre of cell

corners of cell

1 432

5 876

9 121110

13

16


7 ADC 30 ADC 7 ADCshared

17

Signal explanation


Charge sharing

fraction of multi-strip clusters

vsradius charge sharing at

edges/corners

18

Radius µm


Testbeam to do

• Scans at different bias voltages• Scans at different angles• Scans with different thresholds• Residuals


Conclusions

• Pixels successfully mapped

• Efficiencies of the central electrode area found

• 3 - 4% due to central electrode

• Efficiency at corners equivalent to planar device

• Trade-off between efficiency and charge sharing

• Evidence of a decrease in charge sharing in 3D shown

• Pion beam results complement X-ray characterisation

• Higher efficiencies shown

• TOT – spectral evidence of charge sharing and efficiencies

• Trade off in between efficiency and radiation hardness

X-rays

MIPs


Thank you for your attention


Back-UpLateral and Full depletion


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Wire scans and their derivatives

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