electron diffraction apparatus is equipped with a spe-cially designed diffraction tube, whose structure can be observed through a transparent window on the side panel of the apparatus. The electron gun is designed to withstand high voltage with long lifetime. The polycrystalline gold foil target is placed between the electron gun and the screen. Electron beam is accelerated by a high voltage of less than 20 kV to bombard the thin metallic target and hence a dif-fraction phenomenon is generated.