Moving particle composition analyzer

Abstract

Mass spectrometry apparatus for analyzing the composition of moving microscopic particles includes a capacitor having a front electrode upon which the particles impinge, a back electrode, and a solid dielectric sandwiched between the front and back electrodes. In one embodiment, the electrodes and dielectric are arcuately shaped as concentric peripheral segments of different spheres having a common center and different radii. The front electrode and dielectric together have a thickness such that an impinging particle can penetrate them. The front electrode is negatively biased relative to the back electrode so that an impinging particle causes the front and back electrodes to become electrically connected to form a discharge spark between the electrodes. The discharge spark causes ejection from the front electrode of positive ions of elements in the impinging particle. An electric field is formed in front of the front electrode by a grid that is pervious to the particles and ions. The grid is negatively biased relative to the front electrode to draw the ejected positive ions away from the front electrode, so they impinge on a positive ion detector target. The arrival time of different ions is measured to complete the analysis. In a second embodiment, the capacitor has planar, parallel electrodes, in which case the ejected positive ions are deflected downstream of a planar grid by a pair of spaced, arcuate capacitor plates having a region between them through which the ejected ions travel.