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Thallium-doped Cesium Iodide Scintillator Crystal

Thallium-doped Cesium Iodide Scintillator Crystal

$100.00 USD
$100.00 USD
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CsI(Tl) (Thallium-doped Cesium Iodide) is one of the most widely used inorganic scintillator crystals for X-ray and gamma-ray detection, valued for its very high light yield, excellent stopping power, and emission spectrum well matched to silicon photodetectors. By introducing trace amounts of thallium activator ions into the CsI lattice, the scintillation efficiency is significantly enhanced, resulting in bright green emission centered around 550 nm.

Compared with undoped CsI, CsI(Tl) provides substantially higher light output, enabling improved signal-to-noise ratio and reliable energy discrimination in low-to-moderate count-rate applications. Its emission wavelength closely matches the peak sensitivity of photodiodes, avalanche photodiodes (APDs), and silicon photomultipliers (SiPMs), allowing compact, rugged detector designs without the need for UV-sensitive photomultiplier tubes.

With a high effective atomic number (Z) and density (~4.51 g/cm³), CsI(Tl) offers strong absorption efficiency for X-rays and gamma rays, making it suitable for medical imaging systems, security scanners, radiation monitoring instruments, and laboratory spectroscopy setups. While its decay time (~1 µs) is slower than fast scintillators such as pure CsI or LaBr₃, it remains well suited for applications where light yield and detection efficiency are prioritized over timing resolution.

CsI(Tl) crystals are commonly supplied in blocks, plates, pixels, or custom geometries, with optical-grade polishing and optional surface treatments. Due to its slightly hygroscopic nature, CsI(Tl) is typically encapsulated or sealed for long-term stability in practical detector assemblies.

Typical Applications

  • Medical X-ray and CT imaging
  • Gamma-ray spectroscopy
  • Radiation monitoring and dosimetry
  • Security and industrial inspection systems
  • University and national-lab detector research

Below is a clear comparison of the properties of pure CsI, CsI:Tl, and CsI:Na:

Comparison of CsI, CsI:Tl, and CsI:Na

Property CsI:Tl CsI:Na Pure CsI
Light Yield (photons/keV) ~56 ~40 <10
Decay Time ~1 µs ~630 ns <10 ns
Emission Peak ~550 nm ~420 nm 310 nm (fast), 420–600 nm (slow)
Best Detector Compatibility Photodiodes / CCDs PMTs Fast PMTs / UV detectors
Efficiency at Room Temperature Excellent Good Low
Hygroscopic Yes Yes Yes

Frequently Asked Questions — CsI(Tl)

What is CsI(Tl)?
CsI(Tl) is thallium-doped cesium iodide, a high-light-yield inorganic scintillator widely used for X-ray and gamma-ray detection in medical, industrial, and research systems.
What are the main advantages of CsI(Tl)?
CsI(Tl) offers very high light output, excellent stopping power, good energy resolution, and an emission spectrum well matched to silicon photodetectors.
What is the emission wavelength of CsI(Tl)?
CsI(Tl) emits green light with a peak around 550 nm, making it ideal for photodiodes, avalanche photodiodes (APDs), and silicon photomultipliers (SiPMs).
How does CsI(Tl) compare to pure CsI?
CsI(Tl) provides much higher light yield but has a slower decay time (~1 µs). Pure CsI offers ultrafast decay (~6–10 ns) with UV emission but significantly lower light output.
Is CsI(Tl) hygroscopic?
CsI(Tl) is slightly hygroscopic and is typically encapsulated or hermetically sealed to ensure long-term detector stability.
What are typical applications of CsI(Tl)?
Medical X-ray and CT imaging, gamma-ray spectroscopy, radiation monitoring, security scanning systems, and university or national-lab detector research.
Can you provide custom dimensions and polishing?
Yes. CsI(Tl) crystals are available in blocks, plates, pixels, and custom geometries, with optical-grade polishing and surface treatments on request.
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