THE LEIBNIZ-LABOR AMS FACILITY AT THE CHRISTIAN-ALBRECHTS-UNIVERSITY,KIEL, GERMANY

The AMS facility of the Leibniz-Labor fur Altersbestimmung und Isotope nforschung of the Christian-Albrechts Universitat is based on a 3 MV T andetron from High Voltage Engineering Europa (HVEE) with a single ces ium sputter ion source and a separator/recombinator for simultaneous i njecton of the three isotopic carbon beams. The AMS system is similar to those at the Woods Hole Oceanographic Institution, USA, and the Uni versity of Groningen, The Netherland, but it has some new features bas ed on experience at these two facilities. These include improved vacuu m seals, beam diagnostics, X-ray and background suppression as well as a more reliable system control through a PLC-unit with a serial line to the main system computer. The open system design of the beam optics allows significant horizontal and vertical movement of the ion beams without loss to the walls of the system. This leads to plateaus in the response of the isotope beams and ratios to changing values of variou s ion optical elements. Combined with highly stable power supplies, th is gives reproducible measurements. The acceptance tests, g., showed t hat Poisson counting statistics at 0.15% and 0.22% respectively, deter mined the statistical uncertainty in the C-14/C-12 ratios measured for the individual samples of two test series. Strong discrimination of u nwanted ions results in low background count rates in the detector, eq uivalent to an apparent age of 75000 years at present, in spite of the open architecture. Routine measurements since late January 1996(to la te May 1996) have dated 127 unknown samples, mostly foraminifera. The prototype of the carbonate to CO2 conversion system and the graphite s ystem used for the measurements are also described.