Development of a high-rate GEM-based TPC for PANDA

An ungated GEM-based TPC with continuous readout is considered as the central tracker of the PANDA experiment. Particles from up to 2ldr10⁷ p macrp annih./s have to be tracked over a wide momentum range (0.1-8 GeV/c). Simulations demonstrate a space charge accumulation of up to 55 fC/cm³, leading to correctable track distortions of up to 6 mm. Ion backflow studies in triple-GEM structures have been performed. A spatial resolution of down to 140 mum has been achieved with a GEM-TPC test chamber, operated with an Ar/CO₂ gas mixture and without magnetic field, recording the signals of cosmic muons.