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

Original motivation:

Si pixel readout for the Time Projection Chamber (TPC)

at TESLA (now ILC)

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

1995 Giomataris & Charpak: MicroMegas

Wireless wire chambers:better granularity

1996: F. Sauli: Gas Electron Multiplier (GEM)

Wireless wire chambers:better granularity

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

He/Isobutane80/20Modified MediPix

He/Isobutane80/20Modified MediPix

He/Isobutane80/20Non ModifiedMediPix

Americium Source

He/Isobutane80/20Modified MediPix

He/Isobutane80/20Modified MediPix

δ-ray!

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’

‘Try first Micromegas: simpel’

By ‘wafer post processing’at MESA+, Univ. of Twente

InGrid

HV breakdowns

4) Protection Network

1) High-resistive layer

2) High-resistive layer

3) ‘massive’ pads

Other application:

GOSSIP: tracker for intense radiation environment:Vertex detector for SLHC

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

AgeingPower dissipationMaterial budget Rate effectsRadiation hardness EfficiencyPosition resolution

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