Image Number 6 for United States Patent #6784423.
A method for determining the shape and size of particles and their constituent elements is disclosed. Particle ions are accelerated through a mass spectrometer useful in identifying the source particle of the resulting ions. By measuring the time-varying intensity of the identified ions as they strike a detector, a plot of the intensity of the ions over time is obtained for each ionized particle. The size of each ionized particle is determined by measuring a time span corresponding to the width of the peak of this plot. If the detector is a phosphor detector, the shape of the particle may be determined by using a high-speed camera to capture cross-section images of the ion-induced light pattern at closely-spaced successive moments in time. Alternatively, the intensity of ions striking the detector along at least one lateral dimension may be detected. By combining the multiple cross section images or the multiple lateral direction intensity profiles that are thus captured, an actual image of the shape of the original particle can be obtained.
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