Overview Medipix

L. Tlustos, CERNUA9 Meeting, Nov. 2009

Overview Medipix


Medipix ROC’s• Medipix2

– Single pixel pulse processing • event counting

• Timepix – Single pixel pulse processing

• Counting• Time of Arrival• Time over Treshold

• Medipix3– Distributed pulse processing

• “Spectroscopic“ event counting


MEDIPIX2 Collaboration- U INFN Cagliari- CEA-LIST Saclay- CERN Genève- U d'Auvergne Clermont- U Erlangen - ESRF Grenoble - U Freiburg - U Glasgow - IFAE Barcelona - Mitthoegskolan - MRC-LMB Cambridge - U INFN Napoli - NIKHEF Amsterdam - U INFN Pisa - FZU CAS Prague - IEAP CTU in Prague - SSL Berkeley

http://medipix.web.cern.ch/MEDIPIX/


• University of Canterbury, Christchurch, New Zealand • DRT/LIST/DeTeCS/SSTM, CEA, Paris, France • CERN, Geneva, Switzerland, • DESY-Hamburg, Germany • The Diamond Light Source, Diamond House, Didcot, UK• Freiburger Materialforschungszentrum, Albert-Ludwigs-Universität Freiburg,

Germany, • University of Glasgow, Scotland, UK• Institute for Synchrotron Radiation, ISS, Forschungszentrum Karlsruhe, Germany • Biophysical Structural Chemistry, Leiden Univ., The Netherlands • NIKHEF, Amsterdam, The Netherlands • Mid Sweden University, Sundsvall, Sweden • IEAP, Czech Technical University, Prague, Czech Republic • ESRF, Grenoble, France• Universität Erlangen-Nurnberg, Erlangen, Germany • Space Sciences Laboratory, University of California, Berkeley, USA • Microsystems, VTT Information Technology, Espoo, Finland

MEDIPIX3 Collaboration


Current Applications• General purpose imaging detector

– Dental radiography– Mammography– Angiography– Dynamic autoradiography– Tomosynthesis– Synchrotron applications– Electron-microscopy– Gamma camera– X-ray diffraction– Neutron detection– Dynamic defectoscopy – Adaptative optics– Radiation monitor– Mass spectrometry

• Sparse data (mostly Timepix)– Tracking– TPC– Velocity map imaging

• > 150 publications in the last 5 years (http://www.cern.ch/Medipix) • Collaboration spokesman Michael Campbell ([email protected])


Hybrid-Pixel Detektor

p+

n-

ASICn-well

p-substrate

Semiconductor detector

Bump-bond contact

Charged particle

gm

Iin Vout


Medipix2 bump bonding

p+

n-

ASICn-well

p-substrate

Semiconductor detector

Bump-bond contact

Charged particle

gm

Iin Vout

CMOS ROpitch 55 µm

SENSORpitch 55 µm


Medipix ROC’s overviewMEDIPIX2 Timepix MPX3 (design)

Technology CMOS 0.25 mm CMOS 0.25 mm CMOS 0.13 mmType counting counting Counting , Single pixel/

Time over Threshold Counting, charge summingTime of arrival

Pixel size [um] 55 55 55/110Matrix 256 x 256 256x256 256 x 256Area mm2 196 196 196Pixel no. 65536 65536 65536Pixel density [mm-2 ] 330 330 330

Pixel noise ENC 140 e 90 e 75e / 150 eThreshold dispersion 100 e 60 e 55 / 100 adj.Read-out scheme synchronous synchronous synchronousRead-out mode full frame full frame full frame

continuous

Global threshold 1000 e 650 e 1000 eRead-out time 10 ms, 300 ms 10 ms, 300 ms <10 ms

Counter depth 13 13 1, 4, 12, 24

No threshold 2 1 8/4/1

Radiation hardness ~200 krad ~200 krad ~500 Mrad

References:http://medipix.web.cern.ch/MEDIPIXThesis X. Llopart: Design and characterization of 64K pixels chips working in single photon processing modeThe Medipix3 Prototype, a Pixel Readout Chip Working in Single Photon Counting Mode With Improved Spectrometric Performance


Medipix2 Pixel

Analog Digital

Preamp

Disc1

Disc2

Double Disc logic

Vth Low

Vth High

13 bits

Shift Register

Input

Ctest

Testbit

Test Input

Maskbit

Maskbit

3 bits

threshold

3 bits threshold

Shutter

Mux

Mux

ClockOut

Previous Pixel

Next Pixel

Conf8 bits configuration

Polarity

• Positive und negative input signals→ alternative detector materials (GaAs, CdTe …)• Charge sensitive preamplifier with leakage current compensation per pixel• 2 Discriminators with globally adjustable threshold• 3-bit threshold adjustment per pixel• Counter aktiviation via external shutter signal• 1 test-bit and 1 mask-bit per pixel• 13-bit Pseudo-random counter


Medipix Signal Processing

N+ P+Si

Counter:

+

AmplifierComparator

000001

Threshold level >> electronic noise Þ No false counting.

Digital integration (counting)Þ No dark current.

Unlimited dynamic range and exposure time.

Detected count obeys poissonian distribution

Bia

s Vo

ltage

Com

mon

back

-sid

eel

ectro

de

Pix

ella

ted

front

-sid

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de

Pixel electronics

Thresholdlevel

Particle count


Energy window Medipix216.1-19.6 keV 21.6-25.1 keV 29-33.5 keV

36.9-40.4 keV 43.1-46.6

W-Röhre 50 kV2.5 mm Al

DE=3.5 keV


(Random) Application examplesSmall animal CTSpectroscopic dataset for material reconstruction,Mars bio imaging., NZ

Mass spectrometry, Kiev, UAMPX in focal plane of spectrometer, ~10keV ions

PANalyticalIndustrial PartnerTechnology Transfer


(Random) Application examplesSmall animal CTUniv. Erlangen

Neutron imagingLeft: Boron doped Micro channel plate, Univ. CaliforniaRight: LiF converter, IEAP Prague

Phase contrast imagingRight: Propagation phase contrast, IEAP PragueRight: Grating interferometer, PSI


Timepix• Readout chip fully compatible with Medipix2

electronics/software• 3 operational modes

– Counting ( = Medipix2)– Time over threshold mode (~ energy deposited)– Arrival time mode

• Mode can be set in each pixel independently, allowing for concurrent energy and arrival time measurements


TimePix TOT (ADC) Mode withSilicon Detector Layer

N+ P+Si

Counter:

+

AmplifierComparator

000001

Threshold level >> electronic noise Þ No false counting.

Digital integration (counting)Þ No dark current.

Unlimited dynamic range and exposure time.

Detected count obeys poissonian distribution

Bia

s Vo

ltage

Com

mon

back

-sid

eel

ectro

de

Pix

ella

ted

front

-sid

eel

ectro

de

Pixel electronics

Thresholdlevel 007003

Particle countEnergy


Micromegas• A novel approach for the readout of a TPC at the future linear collider

is to use a CMOS pixel detector combined with some kind of gas gain grid

• Using a bare photon counting chip Medipix2 coupled to GEMs (A.Bamberger, M.Titov, Freiburg) or Micromegas (J.Timmermans, NIKHEF) demonstrated the feasibility of such approach

Micromegas

50um


GEM• A novel approach for the readout of a TPC at the future linear collider

is to use a CMOS pixel detector combined with some kind of gas gain grid

• Using a bare photon counting chip Medipix2 coupled to GEMs (A.Bamberger, M.Titov, Freiburg) or Micromegas (J.Timmermans, NIKHEF) demonstrated the feasibility of such approach

GEM


Timepix with 3-GEM detector• DESY testbeam in November 2006 (A.Bamberger, M.Titov)

L. Tlustos, CERNUA9 Meeting, Nov. 2009 Bunch period 176ns (~100ps)


Stopping Heavy Charged ParticlesTotal Energy Resolution

• Am241+ Pu239 combined source

• 5.2 MeV and 5.5 MeV a

• “Heavy” calibration extrapolation

Cluster volume (energy) spectrum (measured in air)

Gaussian fit sigma = 37 keV

0.67%

J. Jakubek et al. / Nuclear Instruments and Methods in Physics Research A 591 (2008) 155–158

Max. spatial resolution ~0.5 μm


11B HIMAC

@ 0 @ 60 @ ~90

Charge deposition studies with various Isotopes → Space Dosimetry


→ Quantum Dosimetry• Different particles have different event signatures Þ use cluster

finding algorithms and decoding of event morphology New application: online dosimetry 15 MPX2 installed in ATLAS

241Am alpha source 55Fe X-ray source 90Sr beta source


Description of the detector

Medipix2 ASIC with 300µm Si sensor + USB interface

Neutron conversion structures:

1) LiF+50µm Al foil area2) 100µm Al foil area3) PE area4) PE+50µm Al foil area5) Uncovered area


Neutron efficiency calibrationFixed HIGH threshold (~200keV)Calibrated efficiency:Thermal: 1.41E-2 ± 7.11E-4 cm-2s-1

252Cf: 1.19E-3 ± 1.89E-5 cm-2s-1

AmBe: 2.86E-3 ± 5.46E-5 cm-2s-1

VDG: 7.23E-3 ± 5.81E-4 cm-2s-1

Thermal neutrons – 500s, 25meV

252Cf – 2000s, 2MeV (mean) AmBe – 2000s, 4MeV (mean)

PE

PE + Al

Al

Uncovered

LiF

X-ray image of conversion layers

Van de Graaff – 1000s, 14MeV

PE / PE+Al cluster count ratio:252Cf: 10.70 ± 0.04

AmBe: 5.18 ± 0.03

VDG: 2.51 ± 0.03


Charge Transport in Planar Detectors

20 keV Photons300 mm Si Sensor55 mm Pixel Pitch 120 V sensor bias

• Mono-energetic Photon spectrum continuous spectrum with constant background and strong contribution of low pulse heights

• Even when using energy window spectroscopic information degraded

Mono-energetic Photons 20 keV


Spectral X-ray source

Photon Spectrum Detected spectrum

Simulation of the effective pulse height distribution as seen by pixel electrodes

Summation of signals from 3x3 pixel cluster

Corrected Pixel Spectrum


Charge Summing Implementation

• Off chip: Timepix like architecture– Digitization of energy deposited in pixel →TOT – Sparse data, no overlaps → limited photon flux– Fast readout necessary

• On chip: Medipix3– Communicating pixels

• Dead time/pileup limit given by shaping time

– Summing of 4 adjacent pixels– 4 (8) Energy bins


55 mm

The winner takes all • Charge is summed in every 4 pixel cluster on an event-by-event basis

Medipix3 - Charge Summing Architecture

• The incoming quantum is assigned as a single hit


MPX3 first results• Just back from

foundry• Extensive testing

going on• + HW integration• + Software• …..• Works, only few

issues found


• In the pipeline– Next generation of RO systems

• RelaxD (Nikhef, Panalytical): 4 chip• Mars (Canterbury): 6 chip• Ruin (IEAP, Prague): single chip• PRIAM for MPX3, ESRF

– New sensors • 150, 300 and 1mm thick Si• GaAs, CdTe• Amorphous Si, Amorphous CdTe (-> rad hard)

• Next ?– “Timepix2”, in discussion for LHCb velo upgrade: square pix,

fast ToT/ToA tracking

Outlook, in general

framerate ≥100 Hz

framerate ≥1 KHz


• 2nd Medipix in Roman Pot 1• 3rd (4th?) Medipix in Roman Pot 2

– In coincidence

• Tracking algorithm • RO upgrade ≥100 Hz framerate• Alternative sensors

– Edgeless sensors (50 mm insensitive area)• Prototypes so far …

– Amorphous Si, amorphous CdTe– 1 mm Si → solid state TPC

Outlook, in particular

Documents

Overview Medipix