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!