A new ion beam cooler and buncher for ISOLTRAP and mass measurements of radioactive argon isotopes - ISOLTRAP is a Penning trap mass spectrometer installed at ISOLDE/CERN. It is set up to measure the mass of short-lived nuclides with a relative accuracy delta m / m of typically 1* 10^-7. In this work an ion beam cooler and buncher based on a linear radio frequency quadrupole trap has been installed and characterized. By this the overall efficiency of the ISOLTRAP spectrometer was increased by three orders of magnitude. This allows for measuring nuclides that are only produced in minute quantities as for instance 33Ar. In this work the mass of 33,34,42,43Ar has been measured with a relative accuracy of about 1* 10^-7. 33Ar with its half-live of only 174 ms is the shortest-lived nuclide ever investigated in a Penning trap. The high accuracy of the mass measurement of 33Ar made a stringent IMME test for the A=33, T=3/2 isospin quartets possible
