The effect of endcap electrode holes on the resonant ejection from an ion trap

The presence of endcap holes greatly influences the performance of an ion trap mass spectrometer. Optimizing the shape and size of the holes may significantly improve ion trap performance. The field contours have been numerically simulated at varying hole sizes and the potentials were numerically fitted. The presence of holes in the electrodes adds higher order negative components to the field inside the trap. The absolute values of the field components were found to increase with increasing hole size. The fitted potentials were then used to reexamine the amplitude response functions. The addition of negative higher order field components produces up to four jump points in the amplitude response function. The new jump points may produce multiple jump phenomena in forward scans as well as a jump condition in the reverse scan mode that has not previously been considered. The shape of the amplitude response function is dependent on the hole size and the amplitude of the dipole excitation waveform at constant buffer gas pressure. The shape of the function has interesting implications for the resonance ejection process. This work provides new insights into the resonance excitation process in nonlinear ion traps.