Micropattern on CMOS pixels

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Micropattern on CMOS pixels
Harry van der Graaf NIKHEF SECOND
WORKSHOP ON LARGE TPC FOR LOW ENERGY RARE EVENT
DETECTIONLPNHE - Paris VI and VII Universities
 PARIS, France 20 December 2004
NIKHEF Maximilien Chefdeville Auke-Pieter
Colijn Alessandro Fornaini Harry van der
Graaf Peter Kluit Jan Timmermans Jan
Visschers Saclay CEA-DAPNIA Paul Colas Yannis
Giomataris Arnaud Giganon Univ.
Twente/Mesa Jurriaan Schmitz CERN/Medipix
Constm Erik Heijne Xavie Llopart Michael
Campbell
Thanks to Wim Gotink Joop Rovenkamp Arnaud
Giganon
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Time Projection Chamber (TPC) 2D/3D Drift
Chamber The Ultimate Wire (drift) Chamber
track of charged particle
E-field (and B-field)
Wire plane
Wire Plane Readout Pads
Pad plane
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• Let us eliminate wires
• wireless wire chambers
• better granularity

Giomataris Charpak 1995 Micromegas
Ideally a preamp/shaper/discriminator channel
below each hole.
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1996 F. Sauli Gas Electron Multiplier (GEM)
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The MediPix2 pixel CMOS chip 256 x 256
pixels pixel 55 x 55 µm2 per pixel - preamp -
shaper - 2 discr. - Thresh. DAQ - 14 bit
counter - enable counting - stop counting -
readout image frame - reset
We apply the naked MediPix2 chip without X-ray
convertor!
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Problem With wires measure charge
distribution over cathode pads c.o.g. is a good
measure for track position With GEMs or
Micromegas narrow charge distribution (only
electron movement)
avalanche
GEM
wire
Micromegas
Cathode pads
Solutions - cover pads with resistive layer -
Chevron pads - many small pads pixels
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A new readout for the TESLA TPC Each GEM hole
gets its own preamp/shaper/discriminator
Our GEM-equipped TPC We have constructed a small
test TPC equipped with three GEM foils which can
be read out by means of the MEDIPIX2 CMOS pixel
sensor. The GEM foils were obtained from the
CERN/Sauli/GEM group hole-to-hole distance
(hexagonal geometry) 140 µm, hole diameter 85
µm, fiducial surface 100 mm x 100 mm, thickness
50 µm.The drift volume (vol. 100x100x100 mm3) is
surrounded by square wire loops, spaced 6.3 mm,
put at decreasing potential. Three GEM foils are
placed 7.4 mm behind the plane of the bottom wire
loop the distance between GEM foils is 1.6
mm. The anode plane, at ground potential, is 6.6
mm below the third GEM foil.
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The MediPix2 pixel CMOS chip
Cathode foil
Drift Space
Gem foils
Support plate
Medipix 2
We apply the naked MediPix2 chip without X-ray
convertor!
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First events, recorded on March 29, 2003. Drift
space irradiated with 55Fe quanta Gas Ar/Methane
90/10
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No source exposed 0.01 s
No source exposed 2 s
No source exposed 2 s
Feb 9, 2004
Fiducial field 14 x 14 mm2
Collected ionisation in 14 x 14 x 100 mm3 during
exposure time Gas Ar/Isobutane 90/10
No source exposed 0.1 s
90Sr source exposed 0.01 s
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With Paul Colas Yannes Giomataris MediPix2
Micromegas
55Fe
Cathode (drift) plane
Drift space 15 mm
Micromegas
Baseplate
MediPix2 pixel sensor Brass spacer block Printed
circuit board Aluminum base plate
Very strong E-field above (CMOS) MediPix!
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MediPix modified by MESA, Univ. of Twente, The
Netherlands
Pixel Pitch 55 x 55 µm2 Bump Bond pad 25 µm
octagonal 75 surface pacivation SiN New Pixel
Pad 45 x 45 µm2
Insulating surface was 75 Reduced to 20
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14 mm
Friday 13 (!) Feb 2004 signals from a 55Fe
source (220 e- per photon) 300 ?m x 500 ?m
clouds as expected
The Medipix CMOS chip faces an electric field of
350 V/50 µm 7 kV/mm !!
We always knew, but never saw the conversion of
55Fe quanta in Ar gas
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Single electron efficiency

• no attachment
• homogeneous field in
• avalanche gap
• low gas gain
• ?
• No Curran or Polya
• distributions but simply

Prob(n) 1/G . e-n/G
Eff e-Thr/G
Thr threshold setting (e-) G Gas amplification
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New trial NIKHEF, March 30 April 2,
2004 Essential try to see single electrons from
cosmic muons (MIPs) Pixel preamp threshold 3000
e- Required gain 5000 10.000 New Medipix New
Micromegas Gas He/Isobutane 80/20 Ar/Isobutane
80/20 He/CF4 80/20 It Works!
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He/Isobutane 80/20 Modified MediPix
Sensitive area 14 x 14 x 15 mm3
Drift direction Vertical max 15 mm
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He/Isobutane 80/20 Modified MediPix
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He/Isobutane 80/20 Modified MediPix
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He/Isobutane 80/20 Non Modified MediPix Amarici
um Source
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He/Isobutane 80/20 Modified MediPix
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He/Isobutane 80/20 Modified MediPix
d-ray!
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• For TPCs all primary electron info is used, only
• diffused by diffusion!
• Simulations TPC performance in view of single
  electron detection
• spatial resolution ( momentum resolution)
• precision dE/dX by cluster counting (M.
  Hauschild)
• multi track separation
• corrections for scattering
• d-ray suppression
• Low diffusion
• low number of clusters?
• Form collaboration to develop TimePix CMOS pixel
  chip
• based on MediPix change pixel counters into
  TDCs
• require full scale! Submit costs 150 kE for 6
  wafers
• MediPix Consortium (CERN based) likes to design
  TimePix1

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INtegrate (Micromegas) GRID and pixel sensor
InGrid
InGrid Pixel chip GridPix
By wafer post processing at MESA, Univ. of
Twente
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Integrate GEM/Micromegas and pixel sensor InGrid
GEM
Micromegas
By wafer post processing
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First InGrid has been delivered Wafer dia. 100
mm 30 fields with a variety of pillar (spacer)
geometry
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HV breakdowns issue for InGrid 2
1) High-resistive layer
3) massive pads
2) High-resistive layer
4) Protection Network
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Vernier, Moire, Nonius effect
Pitch MediPix 55 µm Pitch Micromegas 60
µm Periodic variation in gain per 12 pixels
Non-modified MediPix Modified MediPix has much
less Moire effect
Focussing on (small) anode pad Continues anode
plane is NOT required Reduction of source
capacity!
No charge spread over 2 or 4 pixels
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Modified
Non Modified
focusing
De-focussing Low E-field Low gas gain
InGrid perfect alignment of pixels and grid
holes! Small pad small capacitance!
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• GridPix could become a general way to
• readout gaseous chambers
• Other applications of GridPix
• µ-TPC
• Transition Radiation Detectors
• GOSSIP vertex detector for intense radiation
  environment

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MIP
MIP
Micromegas (InGrid)
Cathode foil
CMOS pixel array
CMOS chip
Drift gap 1 mm Max drift time 15 ns
GOSSIP Gas On Slimmed SIlicon Pixels
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GOSSIP? Ageing Efficiency Position
resolution Rate effects Radiation hardness HV
breakdowns Power dissipation Material budget
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Ageing
Remember the MSGCs

• Little ageing
• the ratio (anode surface)/(gas volume) is very
  high w.r.t. wire chambers
• little gas gain 5 k for GOSSIP, 20 200 k for
  wire chambers
• homogeneous drift field homogeneous
  multiplication field
• versus 1/R field of wire. Absence of high
  E-field close to a wire
• no high electron energy little production of
  chemical radicals
• Confirmed by measurements (Alfonsi, Colas)
• But critical issue ageing studies can not be
  much accelerated!
• Now being set-up with X-ray generator
  (Panalytical/Philips)

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• Spatial resolution pixels down to 20x 20 µm2
  may be useful
• After all TPC! 3D track info
• Counting rate in Super LHC (no Si Vertex
  compatitor)
• 10 tracks/ (cm2 25 ns) ions reach grid within 10
  30 ns
• Radiation hardness
• Replace electron-hole pair generation in Si by
  gas gas amplification
• Sufficient signal charge to eliminate low-noise
  amplifiers in pixels
• CMOS readout circuit only digital gates (130 nm
  technology)
• Material budget only slimmed Si (40 µm), 1 mm
  gas
• Cooling CMOS chip power lt 0.1 W/cm2 use gas
  flow as cooling..
• If it works interesting for ATLAS, CMS, LHCb,
  ALICE, D0 etc

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• How to proceed?
• InGrid 1 available for tests
• rate effects (all except change in drift
  direction)
• ageing (start of test)
• ? Proof-of-principle of signal
  generator Xmas 2004!
• InGrid 2 HV breakdowns, beamtests with MediPix
  (TimePix1 in 2005)
• TimePix convincing 5 institutes to participate
  (we have 3 already!)
• GOSSIPO CMOS chip for Multi Project Wafer test
  chip in 130 nm tech.
• Apply InGrid 2 on ATLAS FE Pixel chip GOSSIP
  proof-of-principle

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Micropattern on CMOS pixels
Harry van der Graaf NIKHEF SECOND
WORKSHOP ON LARGE TPC FOR LOW ENERGY RARE EVENT
DETECTIONLPNHE - Paris VI and VII Universities
 PARIS, France 20 December 2004
NIKHEF Maximilien Chefdeville Auke-Pieter
Colijn Alessandro Fornaini Harry van der
Graaf Peter Kluit Jan Timmermans Jan
Visschers Saclay CEA DAPNIA Paul Colas Yannis
Giomataris Arnaud Giganon Univ.
Twente/Mesa Jurriaan Schmitz CERN/Medipix
Constm Eric Heijne Xavie Llopart Michael
Campbell
Thanks to Wim Gotink Joop Rovenkamp Arnaud
Giganon