Present state and first results of the 4π-detector at SIS/ESR

At the new SIS/ESR facility GSI in Darmstadt a 4π-detector system for charged particles is under construction at present, which is designed for the investigation of central collisions of heavy ions in the energy range up to 2 GeV/u. The already existing part of the detector comprises a forward wall subtending the polar angles below 30 deg. C at full azimuthal coverage, measuring the velocity and the nuclear charge of the fragments. The charged-particle multiplicity beyond 30 deg. C can be measured with a box of multiwire-chambers; a movable set of ΔE-E-telescopes allows for a precise measurement of isotope ratios at all scattering angles. Mounting of the final detector set-up will start in summer 1991. It will be operational in 1992, and will provide full magnetic analysis of the fragments for all scattering angles larger than 7.5 deg. The first physics experiments, the analysis of which has just started, have concentrated on the reaction Au on Au at incident energies from 100 to 400 MeV/u. First results of this reaction at 170 MeV/u can be presented, which have been obtained in a test run in 1990. (author). 8 refs, 10 figs