Mass spectrometer based on the principle of ion cyclotron resonance in which an ion in a magnetic fieldvmoves in a circular orbit at the cyclotron frequency that is characteristic of its m/z value. Ions are coherently excited to a larger radius orbit using a pulse of radio frequency electric field, and their image charge is detected on receiver plates as a time domain signal. Fourier transformation of the time domain signal results in a frequency domain signal that is converted to a mass spectrum based on the inverse relationship between cyclotron frequency and m/z