Status ‘Si readout’ TPC at NIKHEF
NIKHEF Auke-Pieter ColijnAlessandro FornainiHarry van der GraafPeter KluitJan TimmermansJan Visschers
Saclay CEA DAPNIA Maximilien Chefdeville Paul ColasYannis GiomatarisArnaud Giganon
Univ. Twente/Mesa+ Jurriaan Schmitz
CERN/Medipix Constm Erik HeijneXavie LlopartMichael Campbell Thanks to:
Wim GotinkJoop 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 sensorBrass spacer blockPrinted circuit boardAluminum base plate
Micromegas
Cathode (drift) plane
55Fe
Baseplate
Drift space: 15 mm
With Paul Colas & Ioannis Giomataris:MediPix2 & Micromegas
Very strong E-field above (CMOS) MediPix!
He/Isobutane80/20Modified MediPix
Sensitive area:14 x 14 x 15 mm3
Drift direction:Verticalmax = 15 mm
31 March 2004
He/Isobutane80/20Modified MediPix
31 March 2004
He/Isobutane80/20Modified MediPix
31 March 2004
He/Isobutane80/20Modified 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 mmMax 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!) chipAfter all: it is a TPC with 1 mm drift length (parallax!)
Max. drift length: 1 mmMax. drift time: 10 nsResolution: 0.1 mm 1 ns
EfficiencyPosition resolutionRate effectsAgeingRadiation hardnessHV breakdownsPower dissipationMaterial budget
More details in http://www.nikhef.nl/~d90/tesla/NIPHAD_GOSSIP.ppt
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!