Technology to Grow Single Crystals of CsI:Tl and
Fabrication of Radiation Detectors
Technology to grow single crystals of CsI:Tl and fabrication of radiation detectors   Technology to grow single crystals of CsI:Tl and fabrication of radiation detectors
 
Technology to grow single crystals of CsI:Tl and fabrication of radiation detectors


INTRODUCTION

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 CsI:Tl coupled to suitable photo-detectors have exhibited excellent energy resolution of less than 8% at 662 keV, suitable to be used as radiation detectors in gamma-ray spectroscopy applications. The CsI:Tl being less hygroscopic in nature is easier to handle compared to NaI:Tl crystal. Secondly, the emission from CsI:Tl scintillator at 550 nm makes it suitable to be coupled to photo-diodes to fabricate compact devices operating at lower voltages compared to PMT.

BARC has developed a novel crystal growth system based on the modified Bridgman technique to grow high quality, crack-free single crystals of CsI: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 CsI: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 CsI:Tl crystals and fabrication of scintillator detectors using photo-diodes as well as PMTs.

SPECIFICATIONS

Crystal dimension (mm)

:
:

Diameter : 50 mm,
Length : 60 mm
Density [g/cm3] : 4.51
Melting point [°C] : 621
Thermal expansion coefficient [°C-1] : 54 x 10-6
Cleavage plane : none
Hardness (Mohs) : 2
Hygroscopic : slightly
Wavelength of emission max. [nm] : 550
Lower wavelength cutoff [nm] : 320
Refractive index @ emission max : 1.79
Primary Decay time (ns) : 1000
Light yield [photons/keVγ] : 54
Energy resolution : Less than 8% at 662 keV

APPLICATIONS

  • Gamma-ray spectrometer
  • High energy radiation detectors
  • Nuclear Physics Experiments
  • Area monitor
  • Medical imaging
  • Security baggage scanning

REQUIREMENTS FOR COMMERCIAL PRODUCTION

  • Infrastructural Requirements

Space

About 600 sq feet (25x25 sq. ft) roofed area with proper arrangement of cleanness (preferably Class 10,000), dust proof with controlled temperature (25±1°C) and humidity (<55%) with continuous electricity.

Equipment

  • Growth Furnace
  • Dehydration unit
  • Weighing balance
  • Cutting machines
  • PMT and associated electronics for testing
  • Glass blowing facility for sealing
  • Laminar flow bench

Consumables

  • Vacuum desiccators
  • Quartz crucible
  • Raw material
  • Process chemicals (alcohol, optical grease, oil)
  • Emery papers
  • Alumina powder
  • Manpower Requirement
    • One B.Sc. (Physics) and one M.Sc. (Physics) or equivalent degree


  • Power Supply Requirement
    • 220 V, 50 Hz, Single phase, 15 A
 

For details contact :

    Head, Technology Transfer & Collaboration Division,
    BHABHA ATOMIC RESEARCH CENTRE,
    TROMBAY, MUMBAI - 400 085
    Fax : 091-022-25505151
    Email : technology@barc.gov.in

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