Optical measurements of ion trajectories through the vacuum interface of an inductively coupled plasma mass spectrometer.

A flexible laser excited fluorescence system has been used to trace ion trajectories in the first vacuum stage of an inductively coupled plasma mass spectrometer. The system has been used to record the spatial distributions of ions immediately upstream from the sampling cone and in the 10 mm downstream from the cone for a variety of positions of the plasma with respect to the sampling cone. The data were used in turn to test the efficacy of scanning the plasma across the sampling cone to generate maps of ion distributions in the plasma. The maps generated by scanning the plasma across the cone are close approximations of the ion distribution immediately upstream from the sampling cone, but are not representative of distributions in an unperturbed plasma.