A large TPC prototype for an ILC detector

A Time Projection Chamber (TPC) is a candidate for the central tracker of the future International Linear Collider (ILC) detectors. TPCs have already demonstrated very good performance in past collider experiments. In order to obtain one order of magnitude improvement in momentum resolution and the highest possible track recognition efficiency, the Linear Collider TPC (LCTPC) Collaboration is pursuing R&D activities to find the best state-of-the-art technology for the TPC. According to the ILD Letter of Intent, the TPC will have a diameter of 3.6 m and a length of 4.3 m. It should provide 200 space points with pad readout along a particle track, with a spatial resolution of 100 ¿m in the R¿ plane. To achieve these performances, a TPC equipped with Micro Pattern Gaseous Detectors (MPGD) instead of Multiwire Proportional Chambers (MWPC) is needed. Therefore the LCTPC Collaboration has built a large TPC prototype (LPTPC), with a diameter of 750 mm and a length of 600 mm, which can be equipped with Micromegas or GEMs as amplification structures. Since the end of 2008, the LPTPC has been exposed during several weeks to an electron beam of up to 6 GeV at DESY, in presence of a magnetic field of up to 1.0 Tesla. The LPTPC is not only a testing bed for several readout techniques based on MPGDs it is also a unique opportunity to understand the issues which arise when constructing such a large TPC. In this note we will report on the production and the commissioning of the LPTPC as well as the first results of the test beams.