Shocks and Oscillations in the Dynamics of Expanding Coulomb Clouds

Michigan State University, East Lansing MI

Investigators

Abstract

This project will explore possibilities for better control of electron beams. Electron beams are used in an enormous variety of applications in science, technology and medicine, including semiconductor device fabrication and in radiation treatment of cancers which are close to the skin surface. This study is particularly focused on electron beams utilized for imaging the most fundamental atomic level processes at very short time and length scales, a technology that has been called "making the molecular movie". These movies provide unique insights into atomic processes occurring in complex molecules and materials, potentially enabling design of new devices for next generation disruptive technologies such as quantum computing. The electrons in high intensity electron beams are in the space charge dominated regime where strong Coulomb repulsion leads to deleterious effects such as emittance growth. A key aspect of this project develops the concept of dynamical shocks in expanding Coulomb clouds and beams, using a combination of analytic fluid models and large scale computational studies. A surprising prediction is that dynamical shock formation may provide an avenue for reducing emittance by judicious use of beam apertures. We call this effect Coulomb cooling as it has some similarities with evaporative cooling utilized in trapped atom experiments. Applications of the models and methods to plasmas arising in other contexts, such as astrophysics and cluster physics, will also be explored. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.