Certain devices identify and/or isolate specific atomic elements or molecules using physical mechanisms to distinguish the elements or molecules of interest. For example, magnetic sector mass analyzers and quadrupole mass analyzers use magnetic fields and electric fields, respectively, to manipulate flight paths of accelerated ions based on the ions' charge-to-mass ratio. The magnetic sector mass analyzer uses a magnetic field, typically generated by a large magnet, to bend an ion beam through a curved trajectory. The radius of curvature depends on the charge-to-mass ratio of the ions, so a component stream containing ions of various masses spreads into a band that may be analyzed to determine the identity of the ions (e.g., as part of a mass spectrometer) and/or filtered to generate a beam of ions of a specific mass (e.g., as an ion filter for ion implantation). The quadrupole mass analyzer applies an oscillating electric field to an ion beam, allowing only ions of a specific charge-to-mass ratio to pass in a straight line, sending all other ions into chaotic paths. As a result, the quadrupole mass analyzer inherently acts as a filter, selecting ions of a single mass.
A time-of-flight mass spectrometer uses time, rather than space, to separate ions. The time-of-flight mass spectrometer generates a cloud of ions and accelerates the ions into spatially identical flight paths in a field-free drift region, wherein each ion's time of flight is dependent on the charge-to-mass ratio of the ion. Since all ions are generated in one region and accelerated simultaneously, an initial ion cloud separates into subsets: the lightest ions travel faster and arrive at the end of the field-free drift region sooner as compared to heavier ions. By measuring the flight times of ion subsets arriving at an ion detector, the time-of-flight mass spectrometer determines the masses of the detected ions. The time of flight method for distinguishing among ions does not utilize magnetic fields, and resolves masses of heavier ions than can be resolved by magnetic sector or quadrupole mass analyzers.
USPTO Backgrounds
USPTO Backgrounds