A camera for electron diffraction

Abstract

The apparatus described in this paper, which will be called for shortness an electron camera, is intended to study the diffraction patterns formed by the reflection of cathode rays from crystalline surfaces. It differs from the original apparatus used by Davisson and Germer for this purpose in that the method of detection is photographic instead of electrical, and that the energy of the electrons is much greater, being at least 6000 volts (more usually 30,000) instead of about 300. In consequence of the much greater penetrating power of these fast rays it is not necessary to use an elaborate vacuum technique. The principle of the apparatus is that a narrow beam of cathode rays generated in a gas-filled discharge tube is selected by passing through two fine pin-holes and then strikes the crystalline target, where it is diffracted into divergent beams which ultimately strike a photographic plate.