Status ‘Si readout’ TPC at NIKHEF NIKHEFAuke-Pieter Colijn Alessandro Fornaini Harry van der Graaf Peter Kluit Jan Timmermans Jan Visschers Saclay CEA DAPNIAMaximilien Chefdeville Paul Colas Yannis Giomataris Arnaud Giganon Univ. Twente/Mesa+Jurriaan Schmitz CERN/Medipix ConstmErik Heijne Xavie Llopart Michael Campbell Thanks to: Wim Gotink Joop Rovenkamp ECFA Workshop Durham 3/9/2004 PhD student per 1/9/04

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) Proof of principle based on existing Medipix2 readout chip

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

He/Isobutane 80/20 Modified MediPix Sensitive area: 14 x 14 x 15 mm 3 Drift direction: Vertical max = 15 mm 31 March 2004

He/Isobutane 80/20 Modified MediPix 31 March 2004

He/Isobutane 80/20 Modified MediPix 31 March 2004

He/Isobutane 80/20 Modified MediPix δ-ray? 31 March 2004

Example of a track reconstructed This track: #hits = 24 #clusters = 11 length (3d) = 16.8 mm 1.4 e - /mm; 0.65 cl./mm On average: 1.8 e - /mm; 0.5 cl./mm

Detection of single electrons using MediPix2/Micromegas assembly as Direct Pixel Segmented Anode Analysis of cosmic data 31/3-2/4 finalised NIM paper submitted 31/8/04 #pixels hit/mm track length = 1.83 #clusters/mm track length = 0.52 Single electron efficiency 0.9 Moire effects: mismatch in pixel and hole pitch: 60/(60-55) = 12 pixels repetition

Non Modified Modified Explanation for Moire effect:pitch Micromegas holes: 60 μm pitch MediPix pixels:55 μm Periodic position of hole w.r.t. pixel: repeats after 12 pixels!

Modified Non Modified InGrid: perfect alignment of pixels and grid holes! Small pad: small capacitance!

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

Wafer dia.: 100 mm 30 fields with variety of pillar geometry First trials with pillars look OK Some problems with ‘Micromegas’ grid (hope to have first sample in few weeks

INGRID: some first trials Various pitches, shapes

Other applications of TimePixGrid: - μ-TPC (e.g. KABES in NA48/3 ?) - upgrades of TPCs: STAR, ALICE - Transition Radiation Detectors - GOSSIP: tracker for intense radiation environment

CMOS pixel array MIP Micromegas GOSSIP: Gas On Slimmed SIlicon Pixels Drift gap: 1 mm Max drift time: 10 ns MIP CMOS pixel chip Cathode foil

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 preamp FETs GOSSIP:1 mm gas layer + 20 μm gain gap + CMOS (digital!) chip After all: it is a TPC with 1 mm drift length (parallax!) Max. drift length: 1 mm Max. drift time: 10 ns Resolution: 0.1 mm  1 ns

Efficiency Position resolution Rate effects Ageing Radiation hardness HV breakdowns Power dissipation Material budget More details in

Ongoing/Coming activities: Cosmic trigger setup ready New Micromegas available very soon (Paul C.) New Medipix2 available First Ingrid1 tests Simulations Longer term: Ingrid2 together with MediPix Development of Timepix1 (for TPC) and Timepix2 (for GOSSIP) CMOS chips New collaborators are welcomed!