Ion trap device and its adjusting method

Abstract

In an ion trap device including: a plurality of electrodes enclosing an ion trapping space for trapping ions; an RF driving circuit for generating an RF driving voltage; a resonant circuit for amplifying the RF driving voltage and applying an RF high voltage to at least one of the plurality of electrodes; and a tuning circuit for adjusting a resonant frequency of the resonant circuit while keeping the amplitude of the RF high voltage constant, the method of adjusting the ion trap device according to the present invention includes the steps of: adjusting a resonant frequency of the resonant circuit to a frequency of the RF driving voltage; and shifting the resonant frequency of the resonant circuit so that the RF driving voltage increases by a predetermined constant ratio. According to the ion trap device and its adjusting method of the present invention, the phase difference between the RF driving voltage of the RF driving circuit and the RF high voltage, θ, is adjusted to the same value in plural devices even if the parameters of various elements constituting the resonant circuit, such as the inductance or the equivalent resistance, are slightly different from device to device. Thus the influence of the change in the resonant angular frequency Δω when the amplitude of the RF high voltage is changed to the phase difference θ, Δθ, is the same among devices, and the qualities, such as the mass resolution, of all the devices are always set at their optimal, even if the same parameter values are used to determine operation timings of the device.