A time projection chamber for high-rate experiments: Towards an upgrade of the ALICE TPC

作者：Ketzer Bernhard^*

来源：Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment , 2013, 732: 237-240.

DOI：10.1016/j.nima.2013.08.027

• GEM
• TPC
• Ion backflow
• Specific energy loss
• FOPI
• ALICE

A Time Projection Chamber (TPC) is a powerful detector for three-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 of the 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 the 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.

• 出版日期2013-12-21