Phosphors for Radiation Detectors

5Inorganic Halide Scintillators

Yutaka Fujimoto

Graduate School of Engineering, Tohoku University, Sendai, Japan

5.1 Introduction: History of Inorganic Halide Scintillator Research and Development

Scintillation detectors consisting of a scintillator material that is optically coupled to a photosensitive detector are widely used for detection and measurement of energetic photons such as X‐rays and gamma‐rays. These detectors are commonly used in nuclear and particle physics research, medical imaging, diffraction, nondestructive testing, nuclear treaty verification and safeguards, nuclear nonproliferation monitoring, and geological exploration. The discovery and use of scintillator materials can be traced back to 1896 with Calcium tungstate (CaWO₄), which was used following the discovery of the X‐ray. After nearly half a century, the discovery of the photomultiplier tube (PMT) resulted in research into new scintillator materials. One of the major discoveries in these scintillator materials was in 1948–1951 by Hofstadter and Van Sciver, who identified an exceptionally bright scintillator, thallium‐doped sodium iodide (NaI:Tl) [1, 2] and thallium‐doped cesium iodide (CsI:Tl) [3]. These halide crystals can be used in survey meter and X‐ray computed tomography (CT) scanner applications [4, 5]. Meanwhile, the poor energy resolution of the NaI:Tl and CsI:Tl of approximately 7% at 662 keV from a ¹³⁷Cs source limits its performance in radionuclide identification, which has motivated ...