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An Integrated Single Electron Readout System for the TESLA TPC. Ton Boerkamp Alessandro Fornaini Wim Gotink Harry van der Graaf Dimitri John Joop Rovekamp Jan Timmermans David San Segundo Bello Jan Visschers (NIKHEF) LC Workshop Amsterdam, April 2, 2003. Essentials for TPCs:
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An Integrated Single Electron Readout System for the TESLA TPC Ton Boerkamp Alessandro Fornaini Wim Gotink Harry van der Graaf Dimitri John Joop Rovekamp Jan Timmermans David San Segundo Bello Jan Visschers (NIKHEF) LC Workshop Amsterdam, April 2, 2003
Essentials for TPCs: Geometry length, inner & outer diameter: momentum resolution maximum drift time B-field momentum resolution diffusion (gas) ionisation: primary electrons dE/dX -rays drifting electrons: drift velocity, diffusion Gas Amplification: gain, preamp noise, discharges, space charge read-out preamp noise bandwidth
avalanche GEM wire Micromegas Cathode pads Problem Readout of wires: (ion)induced charge on pads, thus wide charge distribution. High spatial precision from centre-of-gravity: Solutions: - Controlled ‘charge leakage’ between pads using resistive layers - ‘Chevron’ pads - (very) many (small) pads: pixels!
At NIKHEF: MediPix 2 pixel sensor: Jan Visschers et al. Cathode foil Drift Space GEM foils base plate MediPix 2
Triple GEM: Cu/Kapton/Cu 5/50/5 m Pitch/Metal Hole/Centre 140/85/85 m GDD-F. Sauli, CERN
MediPix chip Aluminium base plate O-ring gas seal Fixation bar 3 mm brass block printed circuit board
Chamber with GEM works appropriate: - gas gain of 55 per GEM is reached without sparks; - use 3 GEMs to fire Medipix pixels (~2000 e-); - efficiency of collecting primary electrons > 90 % - signal rise time (100 - 200 ns) OK for Medipix.
? Surface charge ? • 75 percent of surface is covered with insulator (polyimide) • MediPix is in R & D stage (chip imperfections, • low yield, critical parameter settings, • ongoing software development) Proof-of-Principle is ongoing...
TimePix CMOS chip • Best pixel geometry: hexagonal, square, rectangular? • Best pixel pitch? • Preamp specifications? Charge signal time development, • amplitude? • - Multi-threshold required? Detection of electron clusters? • Readout architecture: time stamp per pixel, or • per row & column? Output chain? • Time resolution? Common timing effects? • power dissipation? Sleeping mode? • HV breakdown pixel protection?
Suggestion of Jan Visschers: ‘integrate GEM/Micromegas and pixel sensor’ ‘GEM + TimePix’ ‘Micromegas + TimePix’ • TimePix + GasGainGrid • by ‘post-wafer’ processing? • glue Micromegas on TimePix?
If it works…: • - Effordable: 340 kE/m2 (2003) for TESLA TPC; • - replaces anode wires, readout pads • & readout electronics; • - Best possible TPC performance due to • the detection of single electrons: • - position and drift time coordinates; • - dE/dX measurement; • - low occupancy (109 channels!), thus • best possible multi-track separation; • recognition (and suppressing) of -rays; • gas can be optimised for lowest possible diffusion • - little back-migrating ion charge.
No conclusions yet, but we do have plans: • proof-of-principle with MediPix 2; • Integration of MediPix 2 and Micromegas • Tests with MediPix 2 + GasGainGrid in • cosmic rays • muon beam at CERN (H8) • focussed UV laser (single electron) beam • - Development of TimePix CMOS sensor