An ion trap for a mass spectrometer is disclosed. The ion trap includes a ring electrode and first and second electrodes which are arranged on opposite sides of the ring electrode. The ring electrode and the first and second electrodes are configured to generate an electric field based on the received RF signal. The first electrode defines a first aperture and the second electrode defines a second aperture, the first aperture and the second aperture being asymmetric relative to each other and configured to generate a hexapole field.