Fourier transform mass analyzer, mass analysis method and method of making the Fourier transform mass analyzer

摘要

A Fourier transform mass analyzer (30) comprising: a field generator having an inner electrode (50) disposed along an axis; and first and second detection electrodes (60, 70) being outer electrodes concentric with the inner electrode (50) along the axis are positioned to enclose the inner electrode (50) and to define a gap between the inner electrode (50) and the outer electrodes (60, 70), the gap defining an ion trap volume for the ion packets vibrating therein, and wherein the detection electrodes (60, 70) are arranged to detect an image stream of ions located in the space, the field generator further comprising a deflector electrode (140; 141; 142) without a spatially symmetrical counter electrode; the field generator being configured to a time-varying electric field for the injection of ions to be analyzed into the ion trap volume z wherein the first and second detection electrodes (60, 70) receive a respective voltage tap due to the time-varying electric field; anda differential amplifier arranged to provide an output signal based on the difference between the detection signal for the first detection electrode (60, 70) and the detection signal for the second detection electrode (70, 60), characterized in that the deflector electrode (140; 142) and the inner electrode (50) are formed such that the capacitance between the inner electrode (50) and the first detection electrode (60, 70) is substantially equal to the capacitance between the inner electrode (50) and the second detection electrode (70, 60). corresponds; and that the capacitance between the deflector electrode (140; 141; 142) and the first detection electrode (60,70) substantially corresponds to the capacitance between the deflector electrode (140; 141; 142) and the second detection electrode (70,60).