The FOPI detector at SIS/GSI

The FOPI detector system has been assembled at SIS/GSI to study the properties of hot and dense nuclear matter. The program of FOPI was subdivided to permit the start of a specific program from the beginning of SIS operation. Therefore, the completed system which covers nearly the full 4π solid angle has been built in three stages. (1) The forward plastic wall detector was completed in 1990 and has been successfully employed to measure intermediate mass fragment production in reactions of Au on Au at 150 to 1000 A.MeV. (2) The superconducting solenoid and central drift chamber were completed in 1992 and have also been successfully employed to study charged pion production in Au on Au at 1050 A.MeV. (3) The plastic scintillator/Cherenkov barrel and forward drift chamber HELITRON are partially installed and the full commissioning is expected at the beginning of 1995. Results from recent test experiments involving all three phases which demonstrate the detector's ability to identify the rare signals from Kaon and Λ particle production will be presented. (orig.)