Figure 3.

(a) Images of a grating replica taken with the microscope set at 250 kV and the decelerator at (left to right): 0, 100, and 200 kV. There is an increase in magnification of about 20% with the 200 kV potential, as predicted, and some distortions are detectable by sighting along the grating lines. Contrast has been adjusted for uniform appearance. (b) Magnification of image on CCD as a function of the net incident electron energy. Curves are shown for four series of measurements, starting from 200, 230, 250, and 300 kV, and decelerating the beam by up to 220 kV. The “net energy” is corrected for the calibrations of the power supplies (see text). (c) System gain (arbitrary scale) as a function of incident voltage for the decelerator camera with a thin (triangles) or thick (circles) phosphor. The gain is corrected for changes in magnification, and the net energy is corrected for the voltage calibration errors.