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GOSSIP: a vertex detector combining a thin gas layer as signal generator with a Si pixel readout

GOSSIP: a vertex detector combining a thin gas layer as signal generator with a Si pixel readout. Harry van der Graaf, NIKHEF, Amsterdam TIME Workshop, Zürich, Oct 6, 2005. 1906: Geiger tube gaseous detector ionisation: primary electrons (central) anode wire electron multiplication.

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GOSSIP: a vertex detector combining a thin gas layer as signal generator with a Si pixel readout

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  1. GOSSIP: a vertex detector combining a thin gas layer as signal generator with a Si pixel readout Harry van der Graaf, NIKHEF, Amsterdam TIME Workshop, Zürich, Oct 6, 2005

  2. 1906: Geiger tube gaseous detector ionisation: primary electrons (central) anode wire electron multiplication

  3. Geiger-Muller tube Proportional tube Multi Wire Proportional Chamber Drift Chamber Time Projection Chamber MicroStripGasChamber (Oed 1988) 1995 Micromegas (Charpak & Giomataris) 1996 GEM (F. Sauli) Si replaces gas

  4. Micro Patterned Gaseous Detectors GEM • High field created by Gas Gain Grids • Most popular: GEM & Micromegas Micromegas improved granularity : wire chambers react on COG of many electron clouds/clusters

  5. 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

  6. 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) avalanche GEM wire Micromegas Cathode pads Solutions: - cover pads with resisitive layer - ‘Chevron’ pads - many small pads: pixels!

  7. The MediPix2 pixel CMOS chip • 256 x 256 pixels • pixel pitch: 55 x 55 μm2 • Within each pixel: • preamp + shaper + discr • 14-bits counter • discr. thresholds • Developed by MediPix • Consortium, CERN We apply the ‘naked’ MediPix2 chip without X-ray convertor!

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

  9. He/Isobutane 80/20 Modified MediPix δ-ray! Efficiency for detecting single electrons: < 95 %

  10. Integrate GEM/Micromegas and pixel sensor: InGrid ‘GEM’ ‘Micromegas’ By ‘wafer post processing’

  11. Micromegas Electroforming tech. Large areas Large pillar Ø (250 µm) Hybrid detector Manual mounting InGrid Micro-electronic tech. Wafer scale areas Minimum pillar Ø (30 µm) Integrated detector Compact / Mass producible All geometric parameters accurately controlled Gap, Holes, Supporting structures InGrid VS Micromegas

  12. Processing InGrids Strips Litho. 50 µm SU8 UV Exposure Holes Litho. 0.8 µm Al Suspended membrane 50 µm above the wafer Development

  13. Prototypes Hex / Pillars 19 different fields of 15 mm Ø 2 bonding pads / fields Square / Pillars Square / Walls Square / Pillars

  14. Experimental Setup 55Fe collimated source Gas sealed chamber Grid to HV Cathode to HV Anode to ground Connectors to 10 MΩ resistors in series with electrodes

  15. Energy resolution in Argon IsoC4H10 80/20 • Observation of two lines: • Kα @ 5.9 keV • Kβ @ 6.4 keV • FWHM of the Kα distribution • 16.7 % • Gain fluctuations • < 5% Very good energy resolution: Very precise dimensions d < 0.1 μm

  16. Gains in Argon Argon / CO2 mixtures offers good ageing properties (GOSSIP gas) Gain of 104 reachable in Argon CO2 80/20 Ageing studies in a reasonable amount of time (intense X-rays source)

  17. Other applications of GridPix: • μ-TPC • Transition Radiation Detectors • GOSSIP: tracker for intense radiation environment

  18. MIP MIP InGrid Cathode foil CMOS pixel array CMOS chip ‘slimmed’ to 30 μm Drift gap: 1 mm Max drift time: 16 ns GOSSIP: Gas On Slimmed SIlicon Pixels

  19. 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 gas layer + 20 μm avalanche 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

  20. GOSSIP Ageing * Efficiency Position resolution Rate effects * Radiation hardness HV breakdowns * Power dissipation Material budget

  21. Aging test (remember MSGCs….!) • Rate • Current • Deposits Chamber: Same as GridPix, but with polished Al plate as anode instead of MediPix

  22. Rate effects Anode current (gas gain) due to 55Fe quanta calibrated with gas gain G and X-ray intensity Nx: Ianode = G . Nx . 220 e- . qe Irradiation with X-ray tube: No deviation from current proportionality was observed up to 44 MHz of 8 keV X-ray quanta on a detector surface of 100 mm2.

  23. Aging test Half the GridPix was irradiated with 8 keV X-rays. Gas: normal Ar/Methane 90/10, many plastics included. After 0.3 Coulomb/mm2, deposit of carbon polymer on anode is clearly visible. Micromegas is clean (?!) Reduced aging of a GridPix detector versus wire chambers: • ratio of anode surface: thin wire surface versus anode plane (~20x) • low gas gain due to fast signal and low source capacity (~20x) • total factor: 400x • So: no issue for ILC-TPC • So: application as GOSSIP vertex detector in Super LHC seems feasible

  24. HV breakdowns 1) High-resistive layer 3) ‘massive’ pads 2) High-resistive layer Apply RPC principles to limit charge amplitudes

  25. Gas instead of Si vertex detector: • Pro: • no radiation damage in sensor • modest pixel input circuitry: source capacity of only 30 fF • 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  • 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 well-known process • Needs gas flow (but can be used for cooling….)

  26. Next InGrid Study the geometry influence on Resolution, Gain, Ion back flow Optimise detector geometry Protect the chip from discharges High resistive grid, or separated grid segments ApplyInGrid on MediPix2, (TimePix!), PSI 46 pixel chips GridPix (TPC for ILC) TimePix: modify MediPix 2 chip: TDC clock over pixel matrix EUDET (Nikhef-Saclay-Freiburg et al) granted $$$ ! GOSSIP repeat aging test with Ar/CO2 Gossipo: MPW submit for low-noise preamp (Cs = 30 fF) Test with PSI 46 FE pixel chip equipped with InGrid

  27. NIKHEF Harry van der Graaf Jan Timmermans Jan Visschers Maximilien Chefdeville Sipho van der Putten Arno Aarts Saclay CEA DAPNIA Paul Colas Yannis Giomataris Univ. Twente/Mesa+ Jurriaan Schmitz Cora Salm Sander Smits CERN Erik Heine Medipix Consortium Thanks to: Wim Gotink Joop Rovenkamp Gossip: the electronic bubble chamber

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