Patent ID: 8766174

Claim:
A method of correcting for an asymmetry of an electric field in an FT-ICR cell in a radial direction relative to an axis thereof, comprising: (a) providing an FT-ICR cell having a set of mantle electrodes; (b) supplying ions to the FT-ICR cell, wherein the ions are at least one of introduced into the FT-ICR cell, generated in the FT-ICR cell, and retained in the FT-ICR cell from a previous cycle; (c) applying an excitation voltage pulse to a first subset of the mantle electrodes so that the ions are excited onto a revolving orbit within the FT-ICR cell; (d) acquiring an image current transient with the aid of a second subset of the mantle electrodes, the image currents being induced by the revolving ions when passing the electrodes in the second subset; (e) transforming the image current transient into a frequency or mass spectrum and observing an intensity of at least one of the ion signals with frequencies of nv R , v R being a reduced cyclotron frequency, and nv R ±mv M , v M being a magnetron frequency, where n=2, 4, 6, . . . , and m=1, 2, 3, . . . ; and (f) repeating the steps (b) through (e) while adjusting DC voltages supplied to at least one of the mantle electrodes until adjusted DC voltage settings are found which result in a lower observed intensity of the ion signal(s) compared with an initial intensity.