Computer-controlled, variable-frequency power supply for driving multipole ion guides.

A high voltage, variable-frequency driver circuit for powering resonant multipole ion guides is presented. Two key features of this design are (1) the use of integrated circuits in the driver stage and (2) the use a stepper motor for tuning a large variable capacitor in the resonant stage. In the present configuration the available frequency range spans a factor of 2. The actual values of the minimum and maximum frequencies depend on the chosen inductor and the capacitance of the ion guide. Feedback allows for stabilized, computer-adjustable rf amplitudes over the range of 5-500 V. The rf power supply was characterized over the range of 350-750 kHz and evaluated by driving a quadrupole ion guide in an electrospray time-of-flight mass spectrometer.