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Silicon pixel readout for a TPC Jan Timmermans - NIKHEF

Silicon pixel readout for a TPC Jan Timmermans - NIKHEF. Reminder GridPix TimePix news First & new results InGrid First results on protection Future developments. Goals. Gas multiplication GEM or Micromegas foil(s)

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Silicon pixel readout for a TPC Jan Timmermans - NIKHEF

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  1. Silicon pixel readout for a TPCJan Timmermans - NIKHEF • Reminder GridPix • TimePix news • First & new results InGrid • First results on protection • Future developments Vancouver LC workshop

  2. Goals • Gas multiplication GEM or Micromegas foil(s) • Charge collection with granularity matching primary ionisation cluster spread • Needs sufficiently low diffusion gas • dE/dx using cluster counting? ( M. Hauschild @ ECFA LC workshop Vienna) • Proof of principle based on existing Medipix2 readout chip: achieved • Add 3rd coordinate: Medipix2  TimePix (2006) • Integrate grid with pixel chip: Ingrid (new results) Vancouver LC workshop

  3. Results pixel readout gas detectors NIKHEF-Saclay-CERN-Twente 55x55 μm2 pixels δ ray Observation of min. ionising cosmic muons: high spatial resolution + individual cluster counting ! NIM A540 (2005) 295 (physics/0409048)

  4. (from Freiburg GEM+Medipix setup - Andreas Bamberger) Difference between Micromegas and GEM setup understood (simulation Michael Hauschild) Vancouver LC workshop

  5. (from Freiburg GEM+Medipix setup) Vancouver LC workshop

  6. TimePix1(EUDET: Freiburg, Saclay, CERN, NIKHEF) • Distribute clock to full 256x256 pixel matrix • (50-100-160MHz) • Enable counting by first hit after ‘shutter’ opens, until ‘shutter’ closes (common stop); also time-over-threshold possible • Dynamic range 214 x 10 ns = 160 μs • (for the time being) no zero-suppress • to remain fullycompatible with Medipix2 • Shaping time ~200 ns • Extra static discharge protection for the could be considered later • Keep same chip-size, pixel-size, readout protocol • 1st full reticle submit done July 2006

  7. ‘GEM’ ‘Micromegas’ InGrid Integrate GEM/Micromegas and pixel sensor By ‘wafer post processing’ 4” wafer 19 different fields of 15 mm Ø 2 bonding pads / fields Vancouver LC workshop

  8. Materials for our structures • SU-8 negative resist as insulating pillars • Easy to define structures • Wide range of thickness (5 μm to 250 μm) • High precision • Aluminum as conductive grid • Commonly used in microelectronics • Easy to deposit • Easy to pattern Conductive grid Insulating pillars Vancouver LC workshop

  9. InGrid: Integrated Grid Deposit SU-8 Deposit anode UV exposure Deposit metal Pattern metal Develop resist Vancouver LC workshop

  10. Measuring the InGrid signals ( NIM A556 (2006) 490 ) (After 9 months of process tuning and unsuccessful trials) Pulseheight and gain: He + 20% iC4H10 • Gas gains 103 - 6∙104 Vancouver LC workshop

  11. Energy resolution in Argon IsoC4H10 80/20 • Observation of two lines: • Kαat 5.9 keV • Kβ at 6.4 keV • Resolution σE/E = 6.5% • (FWHM = 15.3%) • Gain variations < 5% • Photo peak asymmetry seen • Very good energy resolution Vancouver LC workshop

  12. Gas gains in Argon • Ar / CO2 mixtures offer good ageing properties • Gain of 104 reachable in Ar / CO2 80/20 • Ageing studies in a reasonable amount of time (intense X-rays source) Vancouver LC workshop

  13. Any field structure feasible Vancouver LC workshop

  14. Gain Y. Giomataris/N.I.M. A419 (1998) 239-250 10000 1000 100 10 1 0.001 0.1 0.01 1 Gap (mm) Gain for different gap sizes Maximum predicted in gain vs gap curve d gap thickness V=400Volts V=350Volts V=300Volts p pressure A,B depend on gasmixture Vancouver LC workshop

  15. Gain for different gap sizes • But now we can make measurements 105 500V 40um 450V 55um 400V 35um 75um 104 Gain 103 102 65 55 75 35 45 300 380 460 540 Gap thickness (μm) Grid voltage Vancouver LC workshop

  16. Gain Gain y y x x 1.6 % RMS 2.6 % RMS Homogeneity • Gain measurements scanning the surface of the detector • Homogeneity given by grid quality Vancouver LC workshop

  17. Gain 10μm hole 70 104 50μm hole 50 E(kV.cm-1) 30 Grid 400V 103 10 30 40 0 60 20 40 80 20 Z(μm) 0 10 Hole size (μm) Simulated gain for different hole size • Electric field along z axis decreases with hole size • Different gain expected for different hole size Vancouver LC workshop

  18. Measured gain for different hole size And measurements confirm simulations Gain 104 103 102 Vgrid 460 420 540 500 Vancouver LC workshop

  19. 60 40 Resolution (FWHM %) 30 20 10 Gain 103 104 Energy resolution • Resolution depends on • Primary,attachment,T,P • Collection efficiency (field ratio) • Gain homogeneity & transverse diffusion Vancouver LC workshop

  20. 35um 55um 50 75um 40 Resolution (FWHM %) 30 20 380 500 460 420 Resolution as function of gap Energy resolution • Why a parabolic behavior ? F. Jeanneau et al. NIM A 461 (2001) 84–87 Gain Vgrid Vancouver LC workshop

  21. Sparking • Chip faces 80kV/cm with no protection (unlike the GEM setup) • Degradation of the field, or total destruction of grid but also CMOS chip 10μm Vancouver LC workshop

  22. a-Si Metal pad Solution:high resistive layer • Resistive plate chamber principle • Amorphous silicon deposited • 4um thickness,resistivity ~1011Ω.cm,temperature~250 °C • 2 fields with Micromegas: one protected, one unprotected • First signals recorded; they look the same Vancouver LC workshop

  23. SiProt Protection of CMOS Pixel chip against discharges (sparks) Method: apply high-resistive layer onto chip: Principle: Resistive Plate Chamber Univ. of Neuchatel (IMT): 3 μm of Amorphous Silicon without heating the Si wafer too much….. Put Thorium in gas line:  Radon gas  Alfa decay in gas - clear large (proportional) Alfa signals - also discharges! Like fast short circuit betweenMicromegas & Anode Cathode Drift gap Micromegas Digital scope (dummy) anode wafer Att. network A-Si (3 μm) Vancouver LC workshop

  24. Unprotected: no A-Si layer With protective A-Si layer - smaller initial charge; - 2nd discharge due to charge spread over surface?  segmentation of A-Si layer in ‘pixels’ Vancouver LC workshop

  25. Further Tests and Developments • Investigate possible use of CMS (or Atlas) frontend pixel chip • GOSSIP: very thin gas/pixel detectors as Vertex Detector (LHC/ILC) (TIMEPIX2 with ~1 ns resolution) • Further ageing tests (Gossip)…. • Chip tiling: large(r) detector surfaces (2x2, 2x4 chips) • Through Si connectivity: avoiding bonding wires • Fast readout technology (~5 Gb/s) • Discharge protection! Vancouver LC workshop

  26. NIKHEF Harry van der Graaf Jan Timmermans Jan Visschers Maximilien Chefdeville Sipho van der Putten Arno Aarts Saclay CEA DAPNIA Paul Colas, David Attié Dan Burke,Yannis Giomataris Arnoud Giganon Univ. Twente/Mesa+ Jurriaan Schmitz Cora Salm Victor Blanco Carballo Sander Smits CERN Michael Campbell,Erik Heine Xavi Llopart Thanks to: Wim Gotink Joop Rovenkamp GridPix: the electronic bubble chamber Vancouver LC workshop

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