The Quantum Nature of Electrons

Abstract

Diffraction of individual electrons is considered in this automated experiment in an effort to demonstrate that single electrons exhibit a wave nature. A CRT with a polycrystalline target is used for diffraction and initial display of the pattern. An optical system is used to collect and focus the light from a precise area of the screen onto a photomultiplier tube (PMT) whose anode current is taken as a measure of light intensity. A current follower and integrator circuit are used to convert the photon induced current from the PMT into a voltage level, which is then converted to a digital value by an analog to digital converter. The digital number is read by a microcomputer and stored. A radial scanning method is used to take advantage of the circular symmetry of the diffraction pattern. The area of the screen that must be considered is thus greatly reduced. Such a scan requires that the optical equipment and the PMT must be moved linearly parallel to the CRT face. A description of how this is accomplished with a stepping motor and translation bed is given. The data collection and translation bed movement as well as the data manipulation and display are controlled by a microcomputer. A detailed description of the data conversion and control circuitry and the implementation techniques is given in an accompanying technical report. As the experiment remains unfinished, this paper concludes with a discussion of how the data to be obtained should be analyzed.