Spreadsheet program for calculating secondary electron trajectories in electrostatic fields

With the increasing importance of Low Voltage Scanning Electron Microscopy, the problem of describing the influence exerted by Secondary electron detectors on the path of primary electrons as well as its effects on the trajectories followed by secondary electrons become increasingly important. In situations where uncoated, insulating specimens are studied in an SEM, the additional problem of sample charging also has to be considered. Characterizing these interactions can be very difficult by conventional programming methods. The large number of points and the interdependence of the potentials at all of the points make the “bookkeeping” very difficult to manage. Spreadsheet programs with macroinstruction languages, however, can make these calculations much easier to perform. Not only can spreadsheets be used to calculate the potential field within a microscope column, macro programming can be used to calculate trajectories throughout that field. For the computations described in this paper, Microsoft Excel for the Macintosh was the spreadsheet chosen because of its effective use of the graphics capabilities of the Macintosh.