Two Stability Islands of Quadrupole Mass Filter near q = 0.9 Created by Auxiliary Radio Frequency Voltage

We report the numerical investigations of quadrupole mass filters concerning stability islands created by auxiliary radio frequency (RF) voltage with high and low frequencies near q = 0.9. The islands are located along the q axis near boundary value q = 0.908 with a low a parameter. The analysis is based upon the matrix method for stability diagram calculations and ion trajectory numerical simulation. The trajectory of ion motions is generated using Runge-Kutta–Nystrom–Dormand-Prince (RK–N–DP) order integration. The ion source model with Gaussian distribution of initial positions and transverse velocities is used. In RF-only operation mode, a resolution power of about R0.1 = 600 without peak tails is achieved with a separation time of about 50 RF cycles. Relatively high resolution power of about 2000–3000 is observed in DC+RF separation mode with a low frequency auxiliary RF signal. The boundaries of stability diagram for additional RF voltage with high frequency are strongly diffused until the separation...