High-precision mass measurements of the heaviest elements with SHIPTRAP

High-precision mass measurements in the region of the heaviest elements have been performed at the Penning-trap mass spectrometer SHIPTRAP. In recent experiments the masses of the isotopes 252-255No and 255,256Lr have been measured directly for the first time with an uncertainty as low as 15 keV. In combination with the results of decay-spectroscopy experiments the mass values of superheavy elements up to 270Ds can be pinned down. These mass values give access to the binding energies and provide valuable information on the nuclear structure of superheavy elements as well as input for theoretical models. The recent results allow a mapping of shell effects across the neutron number N=152. Direct mass measurements of superheavy elements (Z>103) are now within reach, as an increase of the overall efficiency of the SHIPTRAP setup will allow studying isotopes produced at a yet smaller production rate the those studied to date. A cryogenic stopping cell provides a gain in the stopping and extraction efficiency by a factor of three or more. The status of the commissioning and the results of the first efficiency determinations are presented.