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: Spatial resolution: 200  m

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

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

Operational 1998 Radial drift field Length: 2 m Outer diameter: 2.6 m Gas mixture: Ne(80%)CO 2 (20%) Readout channels: 15360

Main TPC For 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): Covers the pseudorapidity range of -1.8 < |η| < 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 acceptance of the experiment The 2 FTPCs cover the pseudorapidity range of 2.5 < |η| < 4.0 on both sides of the experiment. 75 cm in diameter and 120 cm long Radial readout Gas mixture: Ar(50%)CO 2 (50%) 9600 readout pads (1.6 x 20 mm 2 )

25 µm aluminized Mylar on Al frame Central Electrode Prototype for tracking and PID via dE/dx <  < 0.9 ~ 3 m diameter drift gas 90% Ne - 10%CO 2 Length 5.1 m Outer diameter 5.6 m E-field: 400 V/cm Drift time ~88 μs Time Projection Chamber largest ever: 88 m 3, 570 k channels

The ALICE TPC becomes real (outer field cage and end plates)

Local Controller DDL - INT Slow-Control Interface TTC-RX BOARD CTRL RCU Slow – Control (1 Mbit – serial link) Detector Link (200 MB / s) (#216) COUNTING ROOM Each TPC Sector is served by 6 Readout Subsystems Front-end bus (200 MB / sec) Local Slow- Control Serial link ON DETECTOR FEC 128 ch Data Compr. FEC 128 ch FEC 128 ch PASA – ADC – DIG.

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