New gaseous detectors: the application of pixel sensors as direct anode NIKHEFAuke-Pieter Colijn Alessandro Fornaini Harry van der Graaf Peter Kluit Jan Timmermans Jan Visschers Maximilien Chefdeville Saclay CEA DAPNIAPaul Colas Yannis Giomataris Arnaud Giganon Univ. Twente/Mesa+Jurriaan Schmitz CERN/Medipix ConstmEric Heijne Xavie Llopart Michael Campbell Thanks to: Wim Gotink Joop Rovenkamp Harry van der Graaf NIKHEF, Amsterdam IEEE-NSS Conference, Rome N17-4, 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 Chamber The Ultimate Wire (drift) Chamber E-field (and B-field) Wire Plane + Readout Pads track of charged particle Wire plane Pad plane

1995Giomataris & 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) wire avalanche Cathode pads GEM Micromegas 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 chip without X-ray convertor!

MediPix2 pixel sensor Brass spacer block Printed circuit board Aluminum base plate Micromegas Cathode (drift) plane 55 Fe Baseplate Drift space: 15 mm MediPix2 & Micromegas Very strong E-field above (CMOS) MediPix!

We always knew, but never saw: the conversion of 55 Fe quanta in Ar gas No source, 1s 55 Fe, 1s 55 Fe, 10s Signals from a 55 Fe source (220 e- per photon); 300  m x 500  m clouds as expected 14 mm The Medipix CMOS chip faces an electric field of 350 V/50 μm = 7 kV/mm !!

Eff = e -Thr/G Thr: threshold setting (#e-) G: Gas amplification Prob(n) = 1/G. e -n/G no attachment homogeneous field in avalanche gap low gas gain  No Curran or Polya distributions but simply: Single electron efficiency

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 – New Medipix New Micromegas Gas: He/Isobutane 80/20 Ar/Isobutane 80/20 He/CF4 80/20 …… It Works!

He/Isobutane 80/20 Modified MediPix Sensitive area: 14 x 14 x 15 mm 3 Drift direction: Vertical max = 15 mm

He/Isobutane 80/20 Modified MediPix

He/Isobutane 80/20 Modified MediPix

He/Isobutane 80/20 Non Modified MediPix Americium Source

He/Isobutane 80/20 Modified MediPix

He/Isobutane 80/20 Modified 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 mm Max 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!) 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

Ageing Power dissipation Material budget Rate effects Radiation hardness Efficiency Position resolution

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!

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/cm 2  Gas Cooling feasible!

Detector Material budget ‘Slimmed’ Si CMOS chip: 30 μm Si Pixel resistive layer1 μm SU8 eq. Anode pads1 μm Al Grid1 μm Al Grid resistive layer5 μm SU8 eq. Cathode1 μm Al

Rate effects time 0Q0Q 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: 2 cm from beam pipe: 10 tracks cm ns 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 3 rd 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 resolution Transversal coordinates limited by: Diffusion: single electron diffusion 0 – 40/70 µm weighed fit: ava 20/30 µm 10 e- per track: σ = 8/10 µm pixel dimensions: 20 x 20 – 50 x 50 μm 2 Note: we MUST have sq. pixels: no strips (pad capacity/noise) Good resolution in non-bending plane! Pixel number has NO cost consequence (m 2 Si counts) Pixel number has some effect on CMOS power dissipation δ-rays: can be recognised & eliminated 3 rd (drift) coordinate limited by: Pulse height fluctuation gas gain (5 k), pad capacity, # e- per cluster With Time Over Threshold: σ = 1 ns ~~ 0.1 mm 0Q0Q 20 ns

Radiation hardness Gas is refreshed: no damage CMOS 130 nm technology: TID NIEL SEU: design/test need only modest pixel input stage

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 - 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 NIKHEFAuke-Pieter Colijn Alessandro Fornaini Harry van der Graaf Peter Kluit Jan Timmermans Jan Visschers Maximilien Chefdeville Saclay CEA DAPNIAPaul Colas Yannis Giomataris Arnaud Giganon Univ. Twente/Mesa+Jurriaan Schmitz CERN/Medipix ConstmEric Heijne Xavie Llopart Michael Campbell Thanks to: Wim Gotink Joop Rovenkamp Harry van der Graaf NIKHEF, Amsterdam IEEE-NSS Conference, Rome N17-4, Oct 19, 2004