Purpose

Tracking: The TPC is discussed as a solution for the outer tracking within the target spectrometer. The required momentum resolution is ~1%, the required vertex resolution ~150um in the xy plane and < 1cm in z direction.

PID: In the momentum range below ~1GeV and above ~2GeV the TPC provides information for particle identification within the target spectrometer. Especially for particles with momenta below ~1GeV this is of great help for the overall PID performance and to supplement the information from the barrel DIRC.

Working principle (in short)

General: 3D tracking device - charged particles ionize detector gas - electric field along cylinder axis separates positive gas ions from electrons - primary electrons drift towards readout anode - gas amplification done by several GEM foils - ungated, continuous operation mode due to HESR beam properties - intrinsic ion feedback suppression by GEM foils - continuous data readout within PANDA DAQ - parallel online data reduction and processing (including tracking)

PID: performed via measurement of mean energy loss per track length (dE/dx), described by Bethe-Bloch-formula, in combination with (obligatory) momentum measurement - PANDA TPC offers to do ~50-100 (fluctuating) energy loss measurements per track - truncated mean algorithm used to get rid off Landau tail and to calculate mean

                

Important values

Geometry: inner radius: 15cm, outer radius: 42cm, length: 150cm, gas volume: 700l, 2 separate chambers (due to beam pipe)

Material budget: ~1.5% X/X0

Detector gas: Ne/CO2 (90/10, maybe admixture of CH4), gas gain: several 1000

Operation: drift field: 400V/cm, 2x2mm pads (100000)

First estimates and simulations

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-- QuirinWeitzel - 10 May 2006