A measuring cell of an ICR mass spectrometer and a method of operating a measuring cell of the ICR mass spectrometer. The method and system trap ions in a first compartment of the ICR measuring cell by generating an electric potential well in the direction of the magnetic field with a minimum of the electric potential well located inside the first compartment. The method and system excite cyclotron motion of the ions trapped in the first compartment. The method and system transfer at least a part of the excited ions from the first compartment to a second compartment of the ICR measuring cell by displacement of a position of the minimum of the electric potential well from the first compartment to the second compartment. The ions are transferred by displacing the position of the minimum of the electric potential well from the first compartment to the second compartment preferably over a period of time equal to or longer than a characteristic period of ion oscillations along the direction of the magnetic field in the electric potential well. The method and system detect ion cyclotron motion of at least a part of the ions in the second compartment.