new gaseous detectors: the application of pixel sensors as direct anode
DESCRIPTION
New gaseous detectors: the application of pixel sensors as direct anode. Harry van der Graaf NIKHEF, Amsterdam IEEE-NSS Conference, Rome N17-4, Oct 19, 2004. NIKHEFAuke-Pieter Colijn Alessandro Fornaini Harry van der Graaf Peter Kluit Jan Timmermans Jan Visschers - PowerPoint PPT PresentationTRANSCRIPT
New gaseous detectors:the application of pixel sensors as direct anode
NIKHEF Auke-Pieter ColijnAlessandro FornainiHarry van der GraafPeter KluitJan TimmermansJan VisschersMaximilien
Chefdeville
Saclay CEA DAPNIA Paul ColasYannis GiomatarisArnaud Giganon
Univ. Twente/Mesa+ Jurriaan Schmitz
CERN/Medipix Constm Eric HeijneXavie LlopartMichael CampbellThanks to:
Wim GotinkJoop Rovenkamp
Harry van der GraafNIKHEF, Amsterdam
IEEE-NSS Conference, RomeN17-4, Oct 19, 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
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 resisitive layer- ‘Chevron’ pads- many small pads: pixels
Cathode foil
Gem foils
Support plate
Medipix 2
Drift Space
The MediPix2 pixel CMOS chip
We apply the ‘naked’ MediPix2 chipwithout X-ray convertor!
MediPix2 pixel sensorBrass spacer blockPrinted circuit boardAluminum base plate
Micromegas
Cathode (drift) plane
55Fe
Baseplate
Drift space: 15 mm
MediPix2 & Micromegas
Very strong E-field above (CMOS) MediPix!
We always knew, but never saw: the conversion of 55Fe quanta in Ar gas
No source, 1sNo source, 1s5555Fe, 1sFe, 1s
5555Fe, 10sFe, 10s
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
After 24 h cosmic ray data and 3 broken chips:
• We can reach very high gas gains with He-based gases (> 100k!)• The MedPix2 chip can withstand strong E-fields (10 kV/mm!)• Discharges ruin the chip immediately (broke 4 in 4 days!)• Measured efficiency: > 0.9; consistent with high gain• Seen MIPs, clusters, δ-rays, electrons, α ‘s……
- In winter 2004: beam tests (dE/dX: e-, pions, muons,……),X-rays (ESRF, Grenoble);
- Development of TimePix 1: TDC per pixel instead of counter
Integrate GEM/Micromegas and pixel sensor: InGrid
‘GEM’ ‘Micromegas’
Monolitic detector by ‘wafer post processing’
HV breakdowns
4) Protection Network
1) High-resistive layer
2) High-resistive layer
3) ‘massive’ pads
GOSSIP: Gas On Slimmed SIlicon Pixels
CMOS pixel array
MIP
Micromegas
Drift gap: 1 mmMax drift time: 15 ns
MIP
CMOS chip‘slimmed’ to 30 μm
Cathode foil
An thin TPC as vertex detector
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 Ar gas)
1 mm gas layer + 20 μm gain gap + CMOS (almost digital!) chipAfter all: it is a TPC with 1 mm drift length (parallax error!)
Max. drift length: 1 mmMax. drift time: 16 nsResolution: 0.1 mm 1.6 ns
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!
Power dissipation
For GOSSIP CMOS Pixel chip:
Per pixel: - input stage (1.8 μA/pixel)- (timing) logic
Futher: data transfer logic
guess: 0.1 W/cm2
Gas Cooling feasible!
Detector Material budget
‘Slimmed’ Si CMOS chip: 30 μm SiPixel resistive layer 1 μm SU8 eq.Anode pads 1 μm AlGrid 1 μm AlGrid resistive layer 5 μm SU8 eq.Cathode 1 μm Al
Rate effects
time
0
Q
20 ns
• ~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:
SLHC @ 2 cm from beam pipe:10 tracks cm-2 25 ns-1
400 MHz cm-2!
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
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; σ = 0.1 mm; σ = 1.6 ns: feasible!• Lorentz angle
• We want fast drifting ions (rate effect)• little UV photon induced avalanches: good quenching gas
Position resolutionTransversal coordinates limited by:• Diffusion: single electron diffusion 0 – 40/70 µm
weighed fit: ava 20/30 µm10 e- per track: σ = 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
• δ-rays: can be recognised & eliminated
3rd (drift) coordinatelimited by:• Pulse height fluctuation• gas gain (5 k), pad capacity, # e- per cluster With Time Over Threshold: σ = 1 ns ~~ 0.1 mm
0
Q
20 ns
Radiation hardness
• Gas is refreshed: no damage• CMOS 130 nm technology: TID
NIELSEU: design/test
• need only modest pixel input stage
Gas instead of SiPro:- 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- 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- Needs gas flow (but can be used for cooling….)
Plans
- InGrid 1 available for tests in November:- rate effects- ageing (start of test: test takes years)
Proof-of-principle of signal generator: Xmas 2004!
- InGrid 2: HV breakdowns, beamtests with MediPix (TimePix1 in 2005)
- Gossipo: Multi Project Wafer test chip
Dummy wafer
New gaseous detectors:the application of pixel sensors as direct anode
NIKHEF Auke-Pieter ColijnAlessandro FornainiHarry van der GraafPeter KluitJan TimmermansJan VisschersMaximilien
Chefdeville
Saclay CEA DAPNIA Paul ColasYannis GiomatarisArnaud Giganon
Univ. Twente/Mesa+ Jurriaan Schmitz
CERN/Medipix Constm Eric HeijneXavie LlopartMichael CampbellThanks to:
Wim GotinkJoop Rovenkamp
Harry van der GraafNIKHEF, Amsterdam
IEEE-NSS Conference, RomeN17-4, Oct 19, 2004