A Time Projection Chamber for High-Rate Experiments: Towards an Upgrade of the ALICE TPC

Abstract

A Time Projection Chamber (TPC) is a powerful detector for 3-dimensional tracking and particle identification for ultra-high multiplicity events. It is the central tracking device of many experiments, e.g. the ALICE experiment at CERN. The necessity of a switching electrostatic gate, which prevents ions produced in the amplification region o MWPCs from entering the drift volume, however, restricts its application to trigger rates of the order of 1 kHz. Charge amplification by Gas Electron Multiplier (GEM) foils instead of proportional wires offers an intrinsic suppression of the ion backflow, although not to the same level as a gating grid. Detailed Monte Carlo simulations have shown that the distortions due to residual space charge from back-drifting ions can be limited to a few cm, and thus can be corrected using standard calibration techniques. A prototype GEM-TPC has been built with the largest active volume to date for a detector of this type. It has been commissioned with cosmics and particle beams at the FOPI experiment at GSI, and was employed for a physics measurement with pion beams. For future operation of the ALICE TPC at the CERN LHC beyond 2019, where Pb-Pb collision rates of 50 kHz are expected, it is planned to replace the existing MWPCs by GEM detectors, operated in a continuous, triggerless readout mode, thus allowing an increase in event rate by a factor of 100. As a first step of the R&D program, a prototype of an Inner Readout Chamber was equipped with large-size GEM foils and exposed to beams of protons, pions and electrons from the CERN PS. In this paper, new results are shown concerning ion backflow, spatial and momentum resolution of the FOPI GEM-TPC, detector calibration, and dE/dx resolution with both detector prototypes. The perspectives of a GEM-TPC for ALICE with continuous readout will be discussed.

Proceedings of the 13th Vienna Conference on Instrumentation (VCI 2013), submitted to Nuclear Instruments and Methods A, 4 pages, 10 figures

References in corpus (3)

• Efficient ion blocking in gaseous detectors and its application to gas-avalanche photomultipliers sensitive in the visible-light range
• Technical Design Study for the PANDA Time Projection Chamber
• Space-Charge Effects in an Ungated GEM-based TPC

Cited by in corpus (16)

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• Study of charging up effect in a triple GEM detector
• Measurements of the Charging-Up Effect in Gas Electron Multipliers
• Study of charging-up effect for a single mask triple GEM detector
• High voltage scheme optimization for secondary discharge mitigation in GEM-based detectors
• Building a large-area GEM-based readout chamber for the upgrade of the ALICE TPC
• Ion backflow studies with a triple-GEM stack with increasing hole pitch
• Concept for an Electron Ion Collider (EIC) detector built around the BaBar solenoid
• Shells in a Toroidal Nucleus in the Intermediate Mass Region
• Reduction of ion back flow using a quadruple GEM detector with various gas mixtures
• Theoretical studies of possible toroidal high-spin isomers in the light-mass region
• Effective gain and Ion Back Flow study of triple and quadruple gem detector
• The upgrade of the ALICE Inner Tracking System