As SEM has the features of large field depth, strong relief perception and high resolution, the analysis of sandstone can use the secondary electron imagery and the back scatter imagery two methods respectively.

Based on the study of secondary electron image characteristics and mechanisms,a secondary electron image system is designed in the text.

The influence of secondary electron emission on efficiency and backflow can be improved through an elaborate electron optics design.

When the instrument was used to determine samples of lower abundance( 235 U abundance less than 1%),the accuracy is poor (relative bias 1%) due to the secondary electrons and strong peak tails of the instrument.

Methods for suppressing secondary electrons in neutron tubes are discussed.

Secondary electron is the most basic and useful signal in Scanning Electron Mi-croscopy, while the generation process of detected secondary electrons is most com-plex.

The mechanism of nanosecond flashover is discussed and the conclusion is reached,that is secondary electron emission avalanche(SEEA) is suit for explaining nanosecond flashover.

With the code, we can calculate the electron density in the chamber with different length of antechamber and the different secondary electron yield respectively.