Characterization of a new open cylindrical ion cyclotron resonance cell with unusual geometry.

A new cylindrical ion cyclotron resonance cell with electrodes of different diameters is characterized. It consists of a central segmented electrode for ion trapping and detection and two planar trapping electrodes with a center bore, to which two small tube electrodes are fitted. The cell can trap either positive or negative ions or both ion polarities in the center region. For trapping both ion polarities, an unsymmetrical double well potential can be generated. Ions generated from SF(6) by electron impact or electron attachment are investigated. In depth analysis of radial excitation patterns of positive and negative ions trapped simultaneously in different stability regions reveals sharp discrimination in the extent of radial acceleration. SIMION simulations of the radial excitation show different trajectories of positive and negative ions. Axial component of radial dipolar excitation field exists in the terminal stability regions.