High resolution mass spectrometry of light ions in a Penning trap

After a brief introduction to the electromagnetic ion trap, we concentrate on the problems related to precise determination of cyclotron frequencies of stored ions. Since these frequency measurements are performed in order to obtain mass ratios we want to point out the inherent difficulties in detecting mass ratios different from 1.0. We then describe the time-of-flight method of detecting ion cyclotron resonance signals. With a small room temperature Penning trap of characteristic size d=1.8 mm in a 7 T magnetic field we study the effect of changing electrical field anharmonicities (i.e. dodecapole term) and of various ton numbers on the cyclotron frequency.