Patent ID: 8969795
Filing Date: 2015-03-03
Classification: H01J

Abstract:
1. A spectrometry system, comprising: at least one ion source that operates at an elevated pressure; at least one spectrometer, comprising at least one of a mass spectrometer and a mobility spectrometer; a curtain gas filter positioned upstream of said at least one spectrometer, said at least one spectrometer having a lower pressure than a pressure of a main volume of said filter; and a passage comprising at least one of a diaphragm and a capillary, placed between said spectrometer and said filter, through which a buffer gas including embedded ions is sucked into said at least one spectrometer, said buffer gas being sucked substantially only from an extraction volume that is substantially smaller than the main filter volume, while the buffer gas substantially other than that in said extraction volume within said main filter volume is exhausted through other openings in the filter, a filter electrode surrounding the at least one of a diaphragm and a capillary; wherein said main filter volume is filled by an ion-source buffer gas supplied from said at least one high-pressure ion source, and wherein said ion-source buffer gas is replaced in said extraction volume by an externally supplied clean buffer gas, and wherein electric fields within the filter push ions of interest from the surrounding ion-source buffer gas into said extraction volume filled by said clean buffer gas, and wherein an ion attracting potential, measured relative to the potential of the passage, is applied to the filter electrode that pulls ions substantially parallel to an axis of ion extraction, and substantially into and around the extraction volume, so that ions of low mobilities having motion substantially influenced by gas-flow forces of said clean curtain gas are substantially guided into said passage, while ions of mobilities higher than a threshold mobility follow substantially lines of the electric field, pass around or through the extraction volume and are attracted to and discharged by said filter electrode, so that substantially all ions having mobilities higher than said threshold mobility are eliminated.