Radiant energy – Ionic separation or analysis – Ion beam pulsing means with detector synchronizing means
Patent
1995-11-02
1997-08-05
Anderson, Bruce
Radiant energy
Ionic separation or analysis
Ion beam pulsing means with detector synchronizing means
250282, B01D 5944, H01J 4900
Patent
active
056545436
ABSTRACT:
A time-of-flight mass spectrometer is disclosed having improved signal to noise characteristics and the ability to reject specific signal ions. The mass spectrometer includes a plasma source that generates the ions, a ion pulser that directs ions toward an ion detector, and a retarding grid assembly charged to repel noise ions. The retarding grid assembly maintains at least a predetermined minimum potential sufficient to repel all ions, except those which have been deliberately sampled by a deliberate pulse of the ion pulser. As a result, noise ions which unintentionally escape the ion pulser are repelled by the retarding grid assembly, and mass peaks are more easily detected and distinguished from background noise. Specific ions of the desired signal are also selectively rejected by stepping up the potential of the retarding grid assembly at a predetermined time calculated to correspond to the time-of-flight of the specific ions from the ion pulser. A grounded grid is also provided to maintain a field-free region away from the retarding grid assembly, such that rejection of ions may be tailored to a narrow range of ion masses.
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Anderson Bruce
Hewlett--Packard Company
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