| 摘要 |
An ungated, time-of-flight ion mass spectrograph utilizing a continuous ion beam that is rastered (swept) by electrostatic deflection plates at the entrance of a time-of-flight drift tube is described. After an ion is deflected, it follows a trajectory in the drift tube that depends on the phase of the raster and is detected by a position-sensitive detector. The detected position provides information concerning the time when the ion entered the drift tube. This information, when combined with knowledge of the raster voltage at the time that the ion was detected, provides a method for determining the time-of-flight of the ion in the drift tube. Using the time-of-flight and the distance traveled in the drift tube, which is also determined by the detected position of the ion, ion speed is determined. Ion mass-per-charge ratio can then be determined for a monoenergetic ion beam. When electrostatic rastering is performed in a direction that is orthogonal to deflection with a constant electric field, the ion speed, energy-per-charge ratio, and mass-per-charge ratio can be determined. The present ungated time-of-flight apparatus permits high duty cycle and therefore, rapid acquisition of mass spectra.
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