Recent developments of the multidrift tube

We describe the latest results in the development of a tracking detector based on a modular concept using multidrift tubes. Several prototypes have been built and tested. Each module contains about 70 independent drift cells, constituted by anodes centred in a hexagonal cell defined by six cathode wires. A thin hexagonal carbon-fibre envelope, 30 mm in diameter, supports the wire tension and provides gas tightness. Using dimethyl ether as a gas filling, we have obtained radial localization accuracies of about 65 μm rms per wire and longitudinal accuracies of about 0.9% of the wire length. Ageing measurements show that we can expect good operation of the modules up to an accumulated charge density of about 1 C/cm. Furthermore, owing to the small cell size and high field, the space-charge gain reduction is less than 10% for currents up to 0.5 μA/cm, about 20 times better than observed in conventional MWPCs. (orig.)