Ion beams are focused beams of positively or negatively charged ions that can be used in electronics manufacturing and sample preparation, for spacecraft propulsion, and to study materials and particles. Ion beams are convenient to work with because they can be easily focused and moved in different directions by electrodes which are connected to adjustable voltage sources.
Preparation of surfaces with ion beams can be done by etching a pattern on the surface with the beam or by ejecting unwanted particles from the surface in a process called sputtering. Ion beams can also be used to implant ions in materials at desired locations.
Another application of ion beams is in recent state-of-the-art spacecraft, such as NASA’s Dawn space probe, which have used ion beams for propulsion. This involves a simple application of action/reaction force pairs. When the ion beam is propelled out of the spacecraft in one direction, the spacecraft experiences a force in the opposite direction. Though the force on the spacecraft is relatively small, very high speeds can be achieved by continuous use of ion beam propulsion for a long period of time.
There are a number of ways to analyze materials and particles using ion beams. High energy, faster moving ion beams are useful for collisional studies in which the ions collide with atoms, molecules, or other ions, and the energy of the impact causes ionization or even breaking apart of the target particle. Low energy, slower moving ion beams can be used to study materials. The low energy of the beam allows more precise measurements of the energies of the electrons, atoms, and molecules that make up the material. For both high and low energy ion beams, studying the charge, speed, quantity, and magnetic alignment of the particles that are ejected after the interaction can provide useful information about the materials and particles involved in the interaction.