Development and studies of a time projection chamber with GEMs

Future high-energy physics experiments will have stringent requirements on the quality of their central tracking systems. In order to evaluate whether a Time Projection Chamber (TPC) in combination with a Micro-Pattern Gas Amplification stage can meet these demands, a small cylindrical prototype has been equipped with two Gas Electron Multipliers (GEMs) and micropads connected to highly integrated front-end electronics. In earlier tests with this system in high-rate particle beams-but without magnetic field-at the Proton-Synchrotron at CERN, high efficiencies and good single-pad-row spatial resolutions could be demonstrated.We now present complementary measurements with this system in high magnetic fields up to 5T at DESY (Hamburg, Germany). Detailed results are given for the spatial resolution dependence on parameters such as drift distance, effective gas gain and magnetic field. Transverse single-pad-row spatial resolution was found to be as low as (53+/-5)μm and a previously published model for the extrapolation of the beam test resulting in large scale operation conditions at the Linear Collider could be confirmed