Abstract: A two-dimensional substantially quadrupole field is established and maintained to trap a selected group of ions. The field has a quadrupole harmonic with amplitude A2, and a higher order harmonic with an amplitude AN, AN being greater than 0.1%. The selected group of ions are trapped in the field. An oscillation frequency at a selected amplitude of excitation for the selected group of ions is determined. An excitation field at the selected amplitude of excitation is added to the two-dimensional substantially quadrupole field to deplete ions within a depletion peak having a low frequency side slightly above the oscillation frequency at the selected amplitude of excitation for the selected group of ions.

Abstract: A numerical control system having both linear and circular interpolating capabilities is described. Data from a permanent storage medium such as tape are input to a preprocessor. The preprocesor processes the data into a form acceptable to the system logic and makes all parameters for both linear and circular interpolation available to the system logic. Because linear interpolation is used, straight lines as well as arbitrary curves which are simulated by a series of short straight line segments can be drawn or cut. Additionally, because circular interpolation is used, arbitrary curves can be simulated by a series of arcs, each of the arcs being a portion of a different circle and the various circles having varying radii in accordance with the dictates of the arbitrary curve being cut or drawn. The ability to use both circular and linear interpolation substantially reduces the data processing because the interpolation technique requiring the least definition can be conveniently employed.