Large multiwire proportional chambers for experiment NA3 at the CERN SPS

Abstract A description is given of large multiwire proportional chambers (sensitive area of about 8 m 2 ) designed and built for the experiment NA3 at CERN. Novel features of these chambers are discussed like, for example, the use of graphite coated cathode planes, spacers with compensating field wires and fast electronics. Details of the fabrication procedure and the performance in the test beam and during experiments are also given.