| 摘要 |
A method and apparatus for collimating ions being emitted from a supersonic expansion nozzle for injection into a time of flight mass spectrometer. Radio frequency fields are used to focus ions toward a desired path, while energy is dissipated from the ions by using a background gas which is advantageously part of a supersonic expansion, giving the background gas a highly organized velocity profile. The background gas absorbs energy when the ions collide with the background gas molecules. By causing the collisional cooling between the ions and the background gas molecules to occur within the supersonic expansion, the ions do not receive velocity distributions determined by ambient thermal energies, but instead enables generation of a highly collimated and high intensity ion beam directed toward the time of flight mass spectrometer.
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