What the client needed

Dr. David Flannigan, Professor in the Department of Chemical Engineering and Materials Science at the University of Minnesota needed an illustration for a journal cover. The Flannigan Research Group uses ultrafast four-dimensional electron microscopy (UEM) to study the dynamics of inorganic, organic, and biological materials with atomic-scale spatial and femtosecond temporal resolutions. In the current study, they simulated what would happen if you shot UV femtosecond laser pulses onto the bottom surface of the Wehnelt cap near the Notice (i.e, aperture) coming up from below at a slight angle. These very short UV pulses generated femtosecond packets of fast moving electrons from the surface of the cap via the photoelectric effect (electrons are emitted only during the photon pulse).  During photoemission, electrons are ejected from the surface of the cap only where the laser hits the material and come off over a wide range of angles before lensing downward toward the Anode plate.  That is, their paths curve downward and enter the approximate center of the Anode plate.