Which type of crystal does the well counter use?

The well counter commonly uses sodium iodide doped with thallium (NaI (Tl)) as its crystal medium. This choice is based on the material's excellent light output and energy resolution properties, which are essential for detecting and quantifying gamma radiation. Sodium iodide crystals produce scintillation light when they interact with ionizing radiation, and adding thallium enhances the scintillation efficiency, making NaI (Tl) particularly suitable for use in well counters.

In a well counter, the radiation emission from a sample is captured within a small well-shaped cavity, and the NaI (Tl) crystal efficiently converts the energy of the incoming gamma photons into visible light. This light is then detected by photomultiplier tubes, leading to the measurement of the radiation.

Other options, like cesium iodide (CsI) and lithium iodide (LiI), also have scintillation properties but do not provide the same combination of light yield and detection efficiency as NaI (Tl) within the context of well counting systems. Ge (germanium) is typically used in high-resolution gamma spectroscopy rather than well counters, due to its different operating principles and requirements, such as the need for cryogenic cooling. Thus, the properties of NaI