[en] This thesis is based on work at the Lund Pelletron accelerator facility in order to improve the accuracy and efficiency of the Lund Accelerator Mass Spectrometry (AMS) system. To obtain high accuracy, all measurements are performed relative to a standard of known activity. Charge state distributions have been obtained for a number of isotopes: ⁹Be, ¹²C, ¹³C, ¹⁶O, ¹⁹F, ²⁷Al, ³⁵Cl, ⁴⁸Ti and ⁵⁸Ni order to improve the transmission through the system and to reduce the isotopic fractionation in the measurements. For carbon, charge states distributions were obtained both under foil and gas stripping. The pressure profile of the Lund Pelletron system has been calculated, both under foil and gas stripping, to make possible to perform transmission calculations for a carbon beam. These results were used to design a new terminal stripper of the accelerator system. A new ion source has, during the last few years, been constructed providing a multiple sample wheel, enabling more accurate relative measurements and also providing more efficient measurements, due to a higher beam current. A new detection technique suitable for AMS measurements on heavier radionuclides, such as ³⁶Cl,⁴⁴Ti and ⁵⁹Ni, has been evaluated and detection limits for ⁵⁹Ni have been derived. 59 refs, 13 figs