Patent ID: 7679051

Claim:
A method of selectively reducing ion counts in an ion mixture in a plasma in space, wherein the mixture has at least a first ion type and a second ion type, the first ion type being lower in mass than the second ion type, the first ion type and the second ion type further comprising ions of an energy range, comprising: receiving the ion mixture into an electrostatic analyzer; wherein the electrostatic analyzer has a toroidal ion path between two deflection plates, the ion path having a first section for applying a DC voltage and a second section for applying an RF frequency voltage to the ions within the ion path; wherein the toroidal ion path receives ions in a 360 degree range of input angles; wherein the first and second sections are adjacent, such that ions enter the first section, pass directly from the first section to the second section and exit the second section; applying a DC voltage across the plates of the first section, wherein the DC voltage has no AC component and is selected to permit only ions within a selected energy band of the energy range to pass from the first section to the second section; and applying an RF voltage across the plates of the second section, and selecting a length of the second section, such that a predominant number of ions of the first ion type undergo at least one oscillation between the plates and are absorbed into the deflection plates before exiting the second path and a predominant number of ions of the second ion type are allowed to exit the second path.