the invention relates to a method and a device for optimization of electric fields in measurement cells of fourier transform ion cyclotron resonance mass spectrometers . the invention is based on the rationale that asymmetric electric fields with uniformly or non - uniformly perturbed field axes can appear in ion cyclotron resonance cells and therefore the axis of the magnetron orbit can become radially displaced . shifted magnetron orbits negatively affect the cyclotron excitation , deteriorate the ft - icr signal , increase the intensity of an even - numbered harmonics peak , lead to stronger side bands of the ft - icr signal , and in extreme cases , cause loss of ions . the present invention helps in probing the shift of the magnetron motion , detecting parameters indicative of the offset of the electric field axis and / or correcting it by trimming it back to the geometric axis of the cell .