TPC in Heavy Ion Experiments

Jørgen A. Lien, Høgskolen i Bergen and Universitetet i Bergen, Norway for the ALICE Collaboration.

Outlook:Presenting some typical TPCs used in Heavy Ion Experiments

•Fixed target – SPS energies: NA49 and CERES/NA45•Collider energies

•RHIC: STAR•LHC: ALICE

TPC constituents

• Drift volume– Linear drift (NA49, STAR central TPC, ALICE)– Radial drift (NA45, STAR forward TPCs)

• Readout chambers– MWPC

• Readout electronics– Analog charge storage, Switched Capacitor Arrays

(SCAs)– Fast digitalisation (ALICE)

• Channels: 182 000• Spatial resolution: 200 m

dE/dx as function of momentum for positive particles produced inp+Pb collisions

dE/dx distribution at a fixed momentum of 10 GeV/c forcentral Pb+Pb collisions

Operational 1998Radial drift fieldLength: 2 mOuter diameter: 2.6 mGas mixture: Ne(80%)CO2(20%)Readout channels: 15360

Main TPCFor tracking and PID via dE/dx

•Collider at RHIC•Operational 2000•Length: 4.2 m•Outer diameter: 4 m•Gas mixture: 10% methane 90 % argon•E-field: 135 V/cm•Readout channels (pads): 136 608•Covers the pseudorapidity range of -1.8 < |η| < 1.8•3000 tracks per event•Pad size: 2.85 mm x 11.5 mm(inner)•Space resolution:~0.5 mm (along pad rows)

STAR Forward TPC:Extend the acceptanceof the experimentThe 2 FTPCs cover the pseudorapidityrange of 2.5 < |η| < 4.0on both sides of the experiment.

75 cm in diameter and 120 cm longRadial readoutGas mixture: Ar(50%)CO2(50%)9600 readout pads (1.6 x 20 mm2)

25 µm aluminized Mylar on Al frameCentral Electrode Prototype

for tracking and PID via dE/dx- 0.9 < < 0.9

~ 3 m diameter

drift gas90% Ne - 10%CO2

Length 5.1 m

Outer diameter 5.6 m

E-field: 400 V/cm

Drift time ~88 μs

Time Projection Chamberlargest ever: 88 m3,

570 k channels

The ALICE TPC becomes real

(outer field cage and end plates)

Loc

al

Con

trol

ler

DD

L - IN

TS

low-C

ontrolInterface

TTC-RX

BOARDCTRL

RCU

Slow – Control(1 Mbit – serial link)

Detector Link(200 MB / s)

(#216)

COUNTING ROOM

1

2

25

Each TPC Sector is served by 6 Readout Subsystems

Front-end bus(200 MB / sec)

LocalSlow- Control

Serial link

ON DETECTOR

FEC128 ch

DataCompr.

FEC128 ch

FEC128 ch

PASA – ADC – DIG.

THE END