New gaseous detectors:

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New gaseous detectors the application of pixel
sensors as direct anode
Harry van der Graaf, NIKHEF, Amsterdam University
of Bonn Oct 14, 2004
NIKHEF Auke-Pieter Colijn Alessandro
Fornaini Harry van der Graaf Peter
Kluit Jan Timmermans Jan Visschers Maximilie
n Chefdeville 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
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Original motivation Si pixel readout for the
Time Projection Chamber (TPC) at TESLA (now ILC)
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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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1995 Giomataris Charpak MicroMegas
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1996 F. Sauli Gas Electron Multiplier (GEM)
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The TPC for the next Linear Collider Ongoing R
D use GEMs or Micromegas instead of
wires 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 resisitive layer -
Chevron pads - many small pads pixels
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A new readout for the ILC - 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 passivation 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 Americi
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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• Nice!
• We can reach very high gas gains with He-based
  gases (gt 100k!)
• The MedPix2 chip can withstand strong E-fields
  (10 kV/mm!)
• Discharges ruin the chip immediately (broke 4 in
  4 days!)
• Efficiency gt 0.9 consistent with high gain
• Seen MIPs, clusters, d-rays, electrons, a s
• in winter 2004 beam tests (dE/dX e-, pions,
  muons,),
• X-rays (ESRF, Grenoble)

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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!
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• Singe electron detection!
• For TPCs
• 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

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Integrate GEM/Micromegas and pixel sensor InGrid
GEM
Micromegas
By wafer post processing
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INtegrate Micromegas GRID and pixel sensor
InGrid
By wafer post processing at MESA, Univ. of
Twente
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First InGrids are there! Wafer dia. 100 mm 30
fields with variety of pillar geometry
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• Other applications of TimePixGrid
• µ-TPC
• Transition Radiation Detectors
• GOSSIP tracker for intense radiation environment

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GOSSIP Gas On Slimmed SIlicon Pixels
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• Essentials of GOSSIP
• Generate charge signal in gas instead of Si
  (e-/ions versus e-/holes)
• Amplify electrons in gas (electron avalanche
  versus FET preamps)
• Then
• No radiation damage in depletion layer or pixel
  preamp FETs
• No power dissipation of preamps
• No detector bias current
• Ultralight detection layer (Si foil)
• 1 mm gas layer 20 µm gain gap CMOS (almost
  digital!) chip
• After all it is a TPC with 1 mm drift length
  (parallax error!)

Max. drift length 1 mm Max. drift time 16
ns Resolution 0.1 mm ? 1.6 ns
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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!

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Efficiency

• Determined by gas layer thickness and gas
  mixture
• Number of clusters per mm 3 (Ar) 10
  (Isobutane)
• Number of electrons per cluster 3 (Ar) - 15
  (Isobutane)
• Probability to have min. 1 cluster in 1 mm Ar
  0.95
• With nice gas eff 0.99 in 1 mm thick layer
  should be possible
• But.
• Parallax error due to 1 mm thick layer, with 3rd
  coordinate 0.1 mm
• TPC/ max drift time 16 ns s 0.1 mm s 1.6
  ns feasible!
• Lorentz angle
• We want fast drifting ions (rate effect)
• little UV photon induced avalanches good
  quenching gas

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Position resolution

• Transversal coordinates limited by
• Diffusion single electron diffusion 0 40/70
  µm
• weighed fit ava 20/30 µm
• 10 e- per track s 8/10 µm
• pixel dimensions 20 x 20 50 x 50 µm2
• Note we MUST have sq. pixels no strips (pad
  capacity/noise)
• Good resolution in non-bending plane!
• Pixel number has NO cost consequence (m2 Si
  counts)
• Pixel number has some effect on CMOS power
  dissipation
• d-rays can be recognised eliminated
• 3rd (drift) coordinate
• limited by
• Pulse height fluctuation
• gas gain (5 k), pad capacity, e- per cluster
• With Time Over Threshold s 1 ns 0.1 mm

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Rate effects
SLHC _at_ 2 cm from beam pipe 10 tracks cm-2 25
ns-1 400 MHz cm-2!

• 10 e- per track (average)
• gas gain 5 k
• most ions are discharged at grid
• after traveling time of 20 ns
• a few percent enter the drift space

time

• Some ions crossing drift space takes 20 200
  µs!
• ion space charge has NO effect on gas gain
• ion charge may influence drift field, but this
  does little harm
• ion charge may influence drift direction change
  in lorentz angle 0.1 rad
• B-field should help

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Data rate Hit Pixel (single electron) data 8
bit column ID 8 bit row ID 4 bit timing
leading edge 4 bit timing trailing
edge total 24 bits/hit pixel 100 e-/ 25 ns
cm2 ? 380 Gb/s per chip (2 x 2 cm2) Cluster
finding reduction factor 10 40
Gb/s Horisberger (PSI) Data rate, DAQ,
data transmission is a limiting factor for
SLHC Required rad hard optical links with 1 mm3
light emittors per chip!
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Radiation hardness

• Gas is refreshed no damage
• CMOS 130 nm technology ? TID
• ? NIEL
• ? SEU design/test
• need only modest pixel input stage
• How is 40 Gb/s hit pixel data transferred?
• need rad hard optical link per chip!

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HV breakdowns
1) High-resistive layer
3) massive pads
2) High-resistive layer
4) Protection Network
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Power dissipation

• For GOSSIP CMOS Pixel chip
• Per pixel
• - input stage (1.8 µA/pixel)
• monostable disc/gate
• Futher data transfer logic
• guess 0.1 W/cm2
• ? Gas Cooling feasible!

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Detector Material budget
Slimmed Si CMOS chip 20 µm Si Pixel resistive
layer 1 µm SU8 eq. Anode pads 1 µm
Al Grid 1 µm Al Grid resistive layer 5 µm
SU8 eq. Cathode 1 µm Al
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• Gas instead of Si
• Pro
• no radiation damage in sensor
• modest pixel input circuitry
• no bias current, no dark current (in absence of
  HV breakdowns..!)
• requires (almost) only digital CMOS readout chip
• low detector material budget
• Typical Si foil. New mechanical concepts
• self-supporting pressurised co-centric balloons
• low power dissipation
• (12) CMOS wafer ? Wafer Post Processing
• no bump bonding
• simple assembly
• operates at room temperature
• less sensitive for X-ray background
• 3D track info per layer
• Con
• Gas chamber ageing not known at this stage

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• How to proceed?
• InGrid 1 available for tests in November
• 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)
• TimePix2 CMOS chip for Multi Project Wafer test
  chip
• GOSSIPO !

Dummy wafer