Precise measurements of ionic masses for QED tests

The Penning trap mass spectrometer SMILETRAP is designed for precision mass measurements using the merits of highly charged ions. In this paper we describe the feature of SMILETRAP and give examples of mass measurements involving Mg11+24, Mg11+26, Ca17+40 and Ca19+40 ions. These emphasize the importance of accurate masses of hydrogen-like and lithium-like ions that are required in the evaluation of g-factor measurements of electrons bound to even-even nuclei and test of QED effects. Highly precise mass measurements can also be used for testing atomic structure calculations and determining atomic binding energies. Relevance of such measurements throughout the periodic system is discussed.