A large prototype of a time projection chamber for a linear collider detector

A Time Projection Chamber (TPC) is a candidate for the central tracker of the ILC detectors. TPCs based on Micropattern Gaseous Detectors (MPGD), described in the ILC Reference Design Report, have dimensions of 2.8–4 m in diameter and 3–4.6 m in length. They are to provide 200 space points with pad readout, along a particle track with the R φ spatial resolution of 100 μ m per row or better. The momentum resolution of δ ( 1 / pt ) ≤ 0.5 × 10 − 4 ( GeV / c ) − 1 is envisaged in the magnetic field of 3–4 T. To realize the excellent space point resolution of 100 μ m , a TPC with MPGD readout instead of the Multiwire Proportional Chamber (MWPC) readout is needed [1] . The MPGD under consideration are Gas Electron Multiplier (GEM) and Micromesh Gas detector (Micromegas). Both detectors are operated either with regular analog pad readout or with the digital TimePix readout. A Large Prototype (LP) of a TPC has been constructed, which has a diameter of about 750 mm and a length of about 600 mm and allows to measure tracks with up to 125 space points with pad readout. This prototype is fitting into a superconducting magnet, installed in a DESY test beam area and is exposed to 6 GeV electrons. A description of the setup as well as first beam results with the various readout options of the LP will be given.