For heavier ion production, for example, an electron cyclotron resonance (ECR) source can be used. Figure 4 shows a schematic diagram of an ECR. At the National Superconducting Cyclotron Laboratory, neutral atoms have their electrons removed using an ECR ion source. ECR works by ionizing the vapor of a desired element such as chlorine and iodine. Further, utilizing this technique metals (Au, Ag, etc.) can also be ionized using a small oven to achieve a vapor phase. The vapor is maintained within a magnetic field long enough for the atoms to be ionized by collisions with electrons. Microwaves are applied to the chamber as to keep the electrons in motion.