Faims apparatus and method for separating ions

A method of controlling an asymmetric waveform generated as a combination of a plurality of sinusoidal waves including two sinusoidal waves having a frequency that differs by a factor of two, the method comprising the steps of:

• sampling the generated asymmetric waveform to determine a plurality of data points from a plurality of different cycles of the generated asymmetric waveform, the plurality of data points being indicative of a shape of the generated asymmetric waveform;
• analyzing the plurality of data points indicative of a shape of the generated asymmetric waveform, the step of analyzing being performed other than in dependence upon an order of magnitude of the data points;
• and,
• in dependence upon the step of analyzing, effecting a change to the generated asymmetric waveform.

A storage medium encoded with machine-readable computer program code for controlling an asymmetric waveform generated as a combination of a plurality of sinusoidal waves including two sinusoidal waves having a frequency that differs by a factor of two, the storage medium including instructions for:

• obtaining a set of data points that is indicative of the generated asymmetric waveform;
• normalizing the data points of the set of data points;
• applying a predetermined function to the normalized data points of the set of data points, to determine a set of resultant values including one resultant value corresponding to each normalized data point of the set of normalized data points;
• determining at least a value relating to the set of resultant values;
• comparing the determined at least a value to template data relating to an ideal asymmetric waveform;
• and,
• in dependence upon the comparison, adjusting at least one of a phase angle difference between the two sinusoidal waves and an amplitude of at least one of the two sinusoidal waves.