Mass-selective instability and resonance ejection modes for DIT with rectangular asymmetric wave shape.

Abstract

We consider the operation of a digital linear ion trap with resonance radial ejection and mass selective instability modes. Periodic wave shape has a positive part with amplitude $V^{+}=V_0$ and duration $0.8T$ and negative part with amplitude $V^{-}=-4V_0$ and duration $0.2T$, where T is the period. The mapping of the stability diagram, calculations of the well's depth and ion oscillations spectra are presented. The process of resonant excitation of ion oscillations by a dipole sinusoidal signal is studied, as well as ion ejection at the stability boundary. The trajectory method is used for this purpose. It is shown that the mass selectivity of dipole excitation is twice as large for rectangular wave shape compared to sinusoidal wave shape. Increasing the diameter of the round rods of the linear trap gives an increase in the resolving power. The possibility of DIT operation in mass-selective instability mode at the boundary point $q_b=0.39$ is discussed.