GB1431736A - Device for measuring electron signals accompanied by strong back-ground noise - Google Patents

Abstract

1431736 Electron spectrometers; electron microscopes NIHON DENSHI KK 12 March 1974 [12 March 1973] 11063/74 Heading H1D [Also in Division H4] In an apparatus in which a specimen 3 is bombarded with a scanned or static primary electron beam 4 and the secondary electrons are analysed in an electrostatic parallel plate energy analyser 5a, 5b, noise adjacent a peak in the secondary electron spectrum is reduced by providing a system which measures the intensity of the spectrum on one or both sides of the peak and subtracts an electrical signal representing that intensity from one representing the peak value. In Fig. 6 the voltage across the the separator is scanned by means of two power supplies 11, 12 added at 10. The output of the analyser is measured by a detector 9 and a signal amplified at 17 is directed by one of gates 18, 19 to a respective integrator 20 or 21 depending on whether the peak value or adjacent values are being passed by the analyser at the time. The outputs of the integrators are subtracted at 22. The output in Fig. 6 is displayed on a cathode-ray tube 32 which is synchronized with primary electron beam 4. Figs. 1, 4 and 7 (not shown) illustrate embodiments with a static primary electron beam in which case the output is measured rather than displayed. In Fig. 4 the integrators and subtractor are replaced by a reversible counter (24). In Figs. 7, 9, 11 (not shown) discrete detectors spatially separated replace the scanning of the energy analyser, respective detectors being allotted to adjacent ranges in the spectrum thus eliminating the need for a timed sequential operation.