Computer reconstruction from electron holograms and observation of fluxon dynamics

Abstract

Customary optical reconstruction, until now a time-consuming process, can be replaced with digital computations to dynamically and quantitatively observe microscopic magnetic fields. Electron holograms of time-varying fields are first recorded on videotape. Next, each hologram is reconstructed and phase amplified by computation. Interference micrographs are then reedited on the videotape and are finally displayed dynamically. Using this method, the movement of magnetic fluxons trapped in a thin superconductive film of lead are observed for the first time near the critical temperature. (The fluxon diameters on the surface look thicker when the sample temperature is raised from 9 K. Fluxons then begin to move near 7 K and finally disappear at the critical temperature 7.2 K.)