Technology to Grow Single Crystals of NaI:Tl and
Fabrication of Radiation Detectors

Technology to grow single crystals of NaI:Tl and fabrication of radiation detectors


Single crystals of alkali halide inorganic scintillators are useful as nuclear radiation detectors in gamma-ray spectroscopy and radiography applications. These crystals are grown in silica crucibles using the vertical Bridgman technique. Crystals of NaI:Tl coupled to photo-multiplier tubes have exhibited excellent energy resolution of less than 7% at 662 keV, suitable to be used as radiation detectors in gamma-ray spectroscopy applications.

BARC has developed a novel crystal growth system based on the modified Bridgman technique to grow high quality, crack-free single crystals of NaI:Tl. Easy extraction of the grown crystal is achieved using a uniquely designed silica crucible and an ingenious furnace design that has precise temperature control mechanism and highly accurate motor for lowering the crucible. Single crystals of NaI:Tl up to 50 mm in diameter and 60 mm in length could be grown with almost 100% yield. The technology also covers processing of the grown NaI:Tl crystals and fabrication of scintillator detectors using photo-multiplier tubes (PMT).

  • Crystal dimension (mm)

: Diameter : 50 mm,
: Length : 60 mm

  • Density [g/cm3]
: 3.67
  • Melting point [°C]
: 651
  • Thermal expansion coefficient [°C-1
: 47.4x10-6
  • Cleavage plane 
: <100>
  • Hardness (Mohs) 
: 2
  • Hygroscopic
  • Wavelength of emission max. [nm]
: 420
  • Refractive index @ emission max
: 1.85
  • Primary Decay time (ns)
: 250
  • Light yield [photons/keVγ]
: 38
  • Energy resolution
: Less than 7% at 662 keV



Infrastructural Requirements

Space :

Equipment :

Consumables :

Manpower Requirement

Electrical Power Requirement

For details contact :

        Head, Technology Transfer & Collaboration Division,
        TROMBAY, MUMBAI - 400 085
        Fax : 091-022-25505151
        Email :