HADES tracking system: First In-beam Experience.

The High Acceptance Di-Electron Spectrometer (HADES) at the heavy ion synchrotron SIS of GSI, Darmstadt, is a high-resolution second generation detector system for lepton pair spectroscopy. Its low-mass tracking system consists of two pairs of planes of trapezoidally shaped Multiwire Drift Chambers (MDC), installed on either side of a superconducting toroidal magnet. This paper summarizes some experiences with the construction and the in-beam operation of the six large-area chambers produced by Forschungszentrum Rossendorf. Studies on creeping of aluminum wires over a period of three years are presented. In addition, the observation of growth of filaments with various shapes and sizes in one of the chambers used in-beam will be discussed in detail.