Ion Trap Quadrupole Mass Filter Secondary Ion Filtering

The patent segments the ion transmission path into distinct functional zones: the ion trap region for selective ion release, the acceleration region for kinetic energy impartment, and the field-free drift region for secondary ion filtering. This spatial segmentation allows ions to be accelerated to detection-sensitive velocities while secondary ions generated during flight are excluded from reaching the detector, as they lack the directional control and energy characteristics of primary ions from the trap.

The patent introduces an intermediary field-free drift region between the acceleration zone and the detector. This intermediary space allows primary ions to maintain their directed motion toward the detector while secondary ions, generated through collisions in this region, are prevented from reaching the detector due to their random trajectories and insufficient energy to overcome the potential barriers at the detector entrance.

The patent extracts the secondary ion filtering function from the traditional electrode-based approach and implements it through the inherent physics of the field-free drift region. By removing the need for additional middle electrodes or complex ion lenses, the design achieves secondary ion rejection through the natural behavior of ions in a field-free environment, where only ions with proper directional momentum from the acceleration zone can reach the detector.

The field-free drift region serves multiple functions simultaneously: it allows primary ions to travel ballistically to the detector, provides space for controlled secondary ion generation that doesn't reach the detector, and acts as an inherent filter without requiring additional active components. The system uses the ions' own kinetic energy and trajectory properties to achieve separation, eliminating the need for external filtering electrodes.