caesium iodide

Caesium iodide (CsI) is an ionic compound often used as the input phosphor of an x-ray image intensifier tube found in fluoroscopy equipment.An important application of caesium iodide crystals, which are scintillators, is electromagnetic calorimetry in experimental particle physics. Pure CsI is a fast and dense scintillating material with relatively high light yield. It shows two main emission components. One in the near ultraviolet region at the wavelength of 310 nm and one at 460 nm. The drawbacks of CsI are a high temperature gradient and a slight hygroscopicity.
See more at Wikipedia.org...