Cesium Iodide is a material with high γ-ray stopping power due to its relative high density and atomic number. For scintillation counting, it is used either in its undoped form or doped with sodium or thallium. CsI is resistant to thermal and mechanical shock. Compared to NaI(Tl), it is relatively soft and plastic, and does not cleave. Because it has no cleavage plane, it is quite rugged. So it is well suited for well logging, space research or other applications where severe shock conditions are encountered.
CsI(pure) has an emission maximum at 315 nm with an intensity much smaller than either of the activated types of this material. The 315 nm emission is characterized by a relatively short decay time of 16 ns, thus the material can be used for fast timing applications.
CsI(Tl) is one of the brightest scintillator. The maximum of the broad emission situated at 550nm is is well suited for photodiode readout. CsI(Tl) is slightly hygroscopic with plastic mechanical properties. Combined with the relatively good radiation hardness properties, CsI(Tl) is well suited for High Energy Physics.
CsI(Na) has a wavelength of emission peak at 420nm and is well matched to the photocathode sensitivity of bialkali photomultiplier and has a light output yielding to 85% of NaI(Tl). Compared to NaI(Tl), it is a relatively soft and plastic material without cleavage plan which makes the material interesting where severe environmental conditions are encountered.
? High γ-ray stopping power
? High density and atomic number
Table1. Main Properties
Thermal expansion coefficient（/℃）
Wavelength of emission max. [nm]
Lower wavelength cutoff [nm]
Refractive index @ emission max
Primary decay time [ns]
Light yield [photons/keVγ]
Photoelectron yield [% of NaI(Tl)] (for γ-rays)
CsI crystal is slightly hygroscopic, please use or keep it in dry environment.
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