A position-sensitive detector system for use in the focal planes of a multigap magnetic spectrograph

In six gaps of the Heidelberg multigap magnetic spectrograph, the conventional nuclear track plates have been replaced by position-sensitive proportional detectors, 1.10 m in length each. The position information is obtained by the method of charge division at a single wire with a resistance of 120 Ω/cm. Each detector consists of two identical counters to allow for background reduction by coincidence measurements to typically 50 nb/sr. A digital processor is used to add and divide the signals. The position resolution, tested by use of a collimated alpha-source, amounts to 1 mm at vertical incidence and to 1.2 mm at an angle of incidence of 300, and thus complies with the requirements given by the intrinsic resolution of the spectrograph. The particle identification is obtained by the energy loss signal. Up to now masses up to A=7 have been separated in experiments. All detectors allow simultaneous operation and on-line registration of 16 one-dimensional spectra per detector. (Auth.)