Post on 05-Jan-2016
Micropattern on CMOS pixels
NIKHEF Maximilien ChefdevilleAuke-Pieter ColijnAlessandro FornainiHarry van der GraafPeter KluitJan TimmermansJan Visschers
Saclay CEA-DAPNIA Paul ColasYannis GiomatarisArnaud Giganon
Univ. Twente/Mesa+ Jurriaan Schmitz
CERN/Medipix Constm Erik HeijneXavie LlopartMichael Campbell
Thanks to:Wim GotinkJoop RovenkampArnaud Giganon
Harry van der Graaf
NIKHEF
SECOND WORKSHOP ON LARGE TPCFORLOW ENERGY RARE EVENT DETECTION
LPNHE - Paris VI and VII Universities PARIS, France 20 December 2004
Time Projection Chamber (TPC): 2D/3D Drift ChamberThe Ultimate Wire (drift) Chamber
E-field(and B-field)
Wire Plane+Readout Pads
track ofchargedparticle
Wire plane
Pad plane
Giomataris & Charpak1995: Micromegas
Ideally: a preamp/shaper/discriminator channel below each hole….
Let us eliminate wires:• wireless wire chambers• better granularity
1996: F. Sauli: Gas Electron Multiplier (GEM)
The MediPix2 pixel CMOS chip
256 x 256 pixelspixel: 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 chipwithout X-ray convertor!
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)
wireavalanche
Cathode pads
GEMMicromegas
Solutions: - cover pads with resistive layer- ‘Chevron’ pads- many small pads: pixels
DriftSpace
GEM foils
MediPix CMOS pixel sensorBrass spacer blockPrinted circuit boardAluminium base plate
Our GEM-equipped TPCWe have constructed a small test TPC equipped with three GEM foils whichcan 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 mmbehind 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.
A new readout for the TESLA TPC:Each GEM hole gets its own preamp/shaper/discriminator:
Cathode foil
Gem foils
Support plate
Medipix 2
Drift Space
The MediPix2 pixel CMOS chip
We apply the ‘naked’ MediPix2 chipwithout X-ray convertor!
First events, recorded on March 29, 2003.Drift space irradiated with 55Fe quantaGas: Ar/Methane 90/10
No source; exposed 0.01 s No source; exposed 2 s No source; exposed 2 s
No source; exposed 0.1 s 90Sr source; exposed 0.01 s
Fiducial field:14 x 14 mm2
Collected ionisationin 14 x 14 x 100 mm3
during exposure timeGas: Ar/Isobutane 90/10
Feb 9, 2004
MediPix2 pixel sensorBrass spacer blockPrinted circuit boardAluminum base plate
Micromegas
Cathode (drift) plane
55Fe
Baseplate
Drift space: 15 mm
With Paul Colas & Yannes Giomataris:MediPix2 & Micromegas
Very strong E-field above (CMOS) MediPix!
MediPix modified by MESA+, Univ. of Twente, The Netherlands
Pixel Pitch: 55 x 55 μm2
Bump Bond pad: 25 μm octagonal75 % surface: pacivation SiNNew Pixel Pad: 45 x 45 μm2
Insulating surface was 75 %Reduced to 20 %
We always knew, but never saw: the conversion of 55Fe quanta in Ar gas
No source, 1sNo source, 1s5555Fe, 1sFe, 1s
5555Fe, 10sFe, 10s
Friday 13 (!) Feb 2004: signals from a 55Fe source (220 e- per photon); 300 m x 500 m clouds as expected
14 mm
The Medipix CMOS chip facesan electric field of 350 V/50 μm
= 7 kV/mm !!
Eff = e-Thr/G
Thr: threshold setting (#e-)G: Gas amplification
Single electron efficiency
0.00
0.20
0.40
0.60
0.80
1.00
0 1000 2000 3000 4000
Threshold setting (number of electrons)
Eff
icie
ncy
(-)
G=500
G=1000
g=2000
g=4000
g=8000
Expon. (G=500)
Expon. (G=1000)
Expon. (g=2000)
Expon. (g=4000)
Expon. (g=8000)
single-electron avalanche distribution
0
0.0005
0.001
0.0015
0.002
0 1000 2000 3000 4000
electrons in avalanche
Pro
b(n
)
G=500
G=1000
G=2000
G=4000
G=8000
Expon. (G=500)
Expon. (G=1000)
Expon. (G=2000)
Expon. (G=4000)
Expon. (G=8000)Prob(n) = 1/G . e-n/G
• no attachment• homogeneous field in avalanche gap• low gas gain
No Curran or Polyadistributions but simply:
Single electron efficiency
New trial: NIKHEF, March 30 – April 2, 2004Essential: try to see single electrons from cosmic muons (MIPs)
Pixel preamp threshold: 3000 e-Required gain: 5000 – 10.000
New MedipixNew Micromegas
Gas: He/Isobutane 80/20Ar/Isobutane 80/20He/CF4 80/20
…… It Works!
He/Isobutane80/20Modified MediPix
Sensitive area:14 x 14 x 15 mm3
Drift direction:Verticalmax = 15 mm
He/Isobutane80/20Modified MediPix
He/Isobutane80/20Modified MediPix
He/Isobutane80/20Non ModifiedMediPix
Amaricium Source
He/Isobutane80/20Modified MediPix
He/Isobutane80/20Modified MediPix
δ-ray!
For TPCs: all primary electron info is used, onlydiffused 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• δ-ray suppression
Low diffusionlow 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
INtegrate (Micromegas) GRID and pixel sensor
‘Micromegas’
By ‘wafer post processing’at MESA+, Univ. of Twente
InGrid
InGrid + Pixel chip=
GridPix
Integrate GEM/Micromegas and pixel sensor: InGrid
‘GEM’ ‘Micromegas’
By ‘wafer post processing’
First InGrid has been delivered
Wafer dia.: 100 mm30 fields with a variety of pillar (spacer) geometry
HV breakdowns: issue for InGrid 2
4) Protection Network
1) High-resistive layer
2) High-resistive layer
3) ‘massive’ pads
Vernier, Moire, Nonius effect
Pitch MediPix: 55 μmPitch Micromegas: 60 μm
Periodic variation in gain per 12 pixels
Focussing on (small) anode padContinues anode plane is NOT requiredReduction of source capacity!
Non-modified MediPixModified MediPix has much less Moire effect
No charge spread over2 or 4 pixels
Modified
Non Modified
InGrid: perfect alignment of pixels and grid holes!Small pad: small capacitance!
focusing De-focussingLow E-fieldLow gas gain
GridPix could become a general way toreadout gaseous chambers
Other applications of GridPix:
- μ-TPC- Transition Radiation Detectors- GOSSIP: vertex detector for intense radiation environment
CMOS pixel array
MIP
Micromegas (InGrid)
GOSSIP: Gas On Slimmed SIlicon Pixels
Drift gap: 1 mmMax drift time: 15 ns
MIP
CMOS chip
Cathode foil
GOSSIP?
AgeingEfficiencyPosition resolutionRate effectsRadiation hardnessHV breakdownsPower dissipationMaterial budget
AgeingRemember 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)
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 < 0.1 W/cm2: use gas flow as cooling…..
If it works: interesting for ATLAS, CMS, LHCb, ALICE, D0 etc
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
Dummy wafer
Micropattern on CMOS pixels
NIKHEF Maximilien ChefdevilleAuke-Pieter ColijnAlessandro FornainiHarry van der GraafPeter KluitJan TimmermansJan Visschers
Saclay CEA DAPNIA Paul ColasYannis GiomatarisArnaud Giganon
Univ. Twente/Mesa+ Jurriaan Schmitz
CERN/Medipix Constm Eric HeijneXavie LlopartMichael Campbell
Thanks to:Wim GotinkJoop RovenkampArnaud Giganon
Harry van der Graaf
NIKHEF
SECOND WORKSHOP ON LARGE TPCFORLOW ENERGY RARE EVENT DETECTION
LPNHE - Paris VI and VII Universities PARIS, France 20 December 2004