A mass spectrometer, comprising: a quadrupole comprising a pair of y rods and a pair of x rods configured to pass an ion stream, the ion stream comprising an abundance of one or more ion species within stability boundaries defined by a and q values; a detector configured to detect the spatial and temporal properties of the abundance of ions, wherein the detector comprises a plurality of dynodes (404, 405, 406), each dynode arranged such that it is struck by ions in a known spatial relationship with the ion stream and the detector further comprises a plurality of charged particle detectors (407, 408, 409), each of the plurality of charged particle detectors associated with one or more of the plurality of dynodes; and a processing means configured to record and store a pattern of detection of ions in the abundance of ions by the dynodes in the detector, characterized in that: the plurality of dynodes in the detector is three dynodes, a first dynode of the three dynodes arranged to be struck by ions in the center of the ion stream, a second dynode being configured to be struck by ions in either a y+ portion of the ion stream or an x+ portion of the ion stream, and a third dynode being configured to be struck by ions in either a y- portion of the ion stream or an x- portion of the ion stream, wherein the y+, y-, x+ and x- portions of the ion stream are related to the x and y pairs of rods of the quadrupole. a quadrupole comprising a pair of y rods and a pair of x rods configured to pass an ion stream, the ion stream comprising an abundance of one or more ion species within stability boundaries defined by a and q values; a detector configured to detect the spatial and temporal properties of the abundance of ions, wherein the detector comprises a plurality of dynodes (404, 405, 406), each dynode arranged such that it is struck by ions in a known spatial relationship with the ion stream and the detector further comprises a plurality of charged particle detectors (407, 408, 409), each of the plurality of charged particle detectors associated with one or more of the plurality of dynodes; and a processing means configured to record and store a pattern of detection of ions in the abundance of ions by the dynodes in the detector, characterized in that: the plurality of dynodes in the detector is three dynodes, a first dynode of the three dynodes arranged to be struck by ions in the center of the ion stream, a second dynode being configured to be struck by ions in either a y+ portion of the ion stream or an x+ portion of the ion stream, and a third dynode being configured to be struck by ions in either a y- portion of the ion stream or an x- portion of the ion stream, the plurality of dynodes in the detector is three dynodes, a first dynode of the three dynodes arranged to be struck by ions in the center of the ion stream, a second dynode being configured to be struck by ions in either a y+ portion of the ion stream or an x+ portion of the ion stream, and a third dynode being configured to be struck by ions in either a y- portion of the ion stream or an x- portion of the ion stream, wherein the y+, y-, x+ and x- portions of the ion stream are related to the x and y pairs of rods of the quadrupole.