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GOSSIP: a vertex detector combining a

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Univ. Twente/Mesa+ Jurriaan Schmitz CERN/Medipix Constm Eric Heijne Xavie Llopart Michael Campbell * Original motivation: Si pixel readout for the Time Projection ... – PowerPoint PPT presentation

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Title: GOSSIP: a vertex detector combining a


1
GOSSIP a vertex detector combining a thin gas
layer as signal generator with a CMOS readout
pixel array
Harry van der Graaf, NIKHEF Vertex 2004,
Menaggio, 17 sept
Gas On Slimmed SIlicon Pixels
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
GOSSIP
2
Original motivation Si pixel readout for the
Time Projection Chamber (TPC) at TESLA (now ILC)
3
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
4
Let us eliminate wires wireless wire
chambers 1996 F. Sauli Gas Electron Multiplier
(GEM)
5
1995 Giomataris Charpak MicroMegas
Ideally a preamp/shaper/discriminator channel
below each hole.
6
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!
7
Cubic drift volume 14 x 14 x 14 mm3
Cathode (drift) plane - 700 V
Drift space 15 mm (gas filled)
Micromegas - 350 V
Baseplate
MediPix2 pixel sensor Brass spacer block Printed
circuit board Aluminum base plate
cosmic muon
Very strong E-field above (CMOS) MediPix!
8
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9
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10
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
11
  • no attachment
  • homogeneous field in
  • avalanche gap
  • low gas gain
  • simple exponential grown
  • of avalanche
  • ?
  • No Curran or Polya
  • distributions but simply

Single electron efficiency
Prob(n) 1/G . e-n/G
Eff e-Thr/G
Thr threshold setting (e-) G Gas amplification
12
New trial NIKHEF, March 30 April 2,
2004 Essential try to see single electrons from
cosmic muons (MIPs) Pixel preamp threshold 3000
e- (due to analog-digital X-talk) Required gain
5000 10.000 New Medipix New Micromegas Gas
He/Isobutane 80/20 !Gain up to 30
k! He/CF4 80/20 It Works!
13
He/Isobutane 80/20 Modified MediPix
Sensitive area 14 x 14 x 15 mm3
Drift direction Vertical max 15 mm
14
He/Isobutane 80/20 Modified MediPix
Sensitive area 14 x 14 x 15 mm3
Drift direction Vertical max 15 mm
15
He/Isobutane 80/20 Modified MediPix
d-ray?
Sensitive area 14 x 14 x 15 mm3
Drift direction Vertical max 15 mm
16
MediPix modified by MESA, Univ. of Twente, The
Netherlands
Non Modified
Modified
Pixel Pitch 55 x 55 µm2 Bump Bond pad 25 µm
octagonal 75 surface passivation Si3N4 New
Pixel Pad 45 x 45 µm2
Insulating surface was 75 Reduced to 20
17
INtegrate Micromegas GRID and pixel sensor
InGrid
By wafer post processing at MESA, Univ. of
Twente
18
  • ! With 1 mm layer of (Ar/Isobutane) gas we have a
    fast TPC!
  • thick enough for 99 MIP detection efficiency
  • thin enough for max. drift time lt 25 ns (LHC
    bunchX)
  • Replace Si sensor amplifier by gas
    layer
  • ? tracker for intense radiation environment

After all until 1990 most vertex detectors were
gas detectors! Si solved granularity problems
associated with wires.
19
GOSSIP Gas On Slimmed SIlicon Pixels
MIP
MIP
Micromegas (InGrid)
Cathode foil
CMOS pixel array
CMOS pixel chip
Drift gap 1 mm Max drift time 16 ns
20
  • 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
  • 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
21
Ageing Efficiency Position resolution Rate
effects Radiation hardness HV breakdowns Power
dissipation Material budget
22
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!

23
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

24
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

25
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

26
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 Data rate, DAQ, data
transmission is a limiting factor for
SLHC Required rad hard optical links with 1 mm3
light emittors per chip!
27
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!

28
HV breakdowns
1) High-resistive layer
3) massive pads
2) High-resistive layer
4) Protection Network
29
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!

30
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
31
  • 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 ?
    dicing 12 pcs
  • 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

32
  • How to proceed?
  • InGrid 1 available for tests in October
  • 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
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