Construction and performance of the proportional chambers for a magnetic spectrometer

The structure technology of fabrication and performance of the multiwire proportional chambers designed as a part of the magnetic spectrometer detecting equipment are described. The chamber dielectric frames are made of the epoxy-compound by the injection moulding method. Wire electrodes were cleaned by ultrasonics in washing solutions. Fabrication and cleaning quality control was performed by observing a glow discharge at high voltage supplied to the chamber. The results of measurements made during the chamber performance testing by means of β--source are presented. The efficiency plateau is 200-300 V when the Ar+30%CO2+0.2% freon-13 B1 gas mixture is used. The electrostatic instability of 620 mm long signal wires is observed. It leads to high noise level in all the channels. By introducing the suport line the noise level has been decreased by a factor of 6