“Linearizing” an ion cyclotron resonance cell

We describe an ion cyclotron resonance (ICR) mass spectrometer that we have built. The design of the instrument was guided in large measure by theoretical consideration; in particular we wished to investigate the effects of improved electrostatic linearity on ICR performance. We found, for instance, that the trap’s performance as a mass spectrometer is essentially independent of the trapping potential. By studying both cyclotron and magnetron modes we were able to characterize both the trap and the magnet. Further, we were able to separate effects of image charge from space charge; this gave us measurements of ion number and ion cloud shape. Finally, we show that the instrument readily provides accurate mass measurements with minimal calibration.