An Integrated Single Electron Readout System for the TESLA TPC Ton Boerkamp Alessandro Fornaini Wim...

AnIntegratedSingle ElectronReadout Systemfor theTESLA TPC

Ton BoerkampAlessandro FornainiWim GotinkHarry van der GraafDimitri JohnJoop RovekampJan TimmermansDavid San Segundo BelloJan Visschers(NIKHEF)

LC WorkshopAmsterdam, April 2, 2003

Essentials for TPCs:

Geometry length, inner & outer diameter:

momentum resolutionmaximum drift time

B-field momentum resolutiondiffusion

(gas) ionisation: primary electronsdE/dX-rays

drifting electrons: drift velocity, diffusion

Gas Amplification: gain, preamp noise, discharges,

space charge

read-out preamp noisebandwidth

Aleph TPC: well optimised, but now there is something new….

1995 Giomataris & Charpak: MicroMegas

1996: F. Sauli: Gas Electron Multiplier (GEM)

ProblemReadout of wires: (ion)induced charge on pads, thuswide charge distribution. High spatial precision fromcentre-of-gravity:

wireavalanche

Cathode pads

GEMMicromegas

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

GEM foils

base plate

MediPix 2

Drift Space

Triple GEM: Cu/Kapton/Cu 5/50/5 mPitch/Metal Hole/Centre 140/85/85 mGDD-F. Sauli, CERN

Aluminium base plate

MediPix chip

3 mm brass block

printed circuit board

O-ring gas sealFixation bar

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 ?

Proof-of-Principle is ongoing...

-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)

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