Thallium Doped Sodium Iodide NaI(Tl)
Single crystal sodium iodide doped with thallium ions is a classic scintillator for detecting gamma-radiation of intermediate and low energies. High luminescence efficiency, wide variety of sizes and geometries and relatively low-cost make NaI(Tl) the most widely used scintillator.
NaI(Tl) scintillators have the greatest light output among all the scintillators and a convenient emission range coinciding with a maximum efficiency of photomultipliers with bialkali photocathodes.
NaI(Tl) crystals have radiation hardness that is quite satisfactory for many applications. They can be used under γ-radiation with flux density of up to 105 photons/(s*cm2) without any noticeable variation of their characteristics.
A serious drawback of NaI(Tl) scintillators is their high hygroscopicity, due to which these crystals must be placed into hermetically sealed housing (container).
Wide application of NaI(Tl) crystals is mainly due to relative simplicity of using and low cost of crystals. Because of favorable combination of physical properties, NaI(Tl) scintillators are widely used in different detecting systems in radiation medicine, in apparatus for monitoring of radionuclides, in nuclear physics, high energy physics, etc.
- high light output
- single crystal or polycrystalline form
- good matching of the radioluminescence spectrum to the maximum sensitivity region of the commonly used PMT and fast response
- high mechanical hardness characteristics (only for the polycrystalline)