CsI, or cesium iodide, is a chemical compound made up of cesium and iodine. It is often used in various applications, including medical imaging and radiation detection, due to its ability to efficiently convert X-rays into visible light. This property makes it valuable in scintillation detectors, which are devices that measure ionizing radiation. In addition to its use in detectors, CsI is also utilized in the production of crystals for optical devices and phosphors. Its high density and atomic number contribute to its effectiveness in these applications, making it a significant material in both scientific and industrial fields.