Development of Tl-based Novel (La, Gd, Ca) Chloride Scintillators for Radiation Detection

by Arshad Khan (Ph.D Candidate)

Tuesday May 26, 2020, 4:30 PM → 5:30 PM Asia/Seoul

216-1호 (제1과학관)

Inorganic single crystal scintillators have widespread applications in modern days radiations detector technology. These applications include high energy physics experiments, nuclear physics, medical imaging, homeland security, oil well lodging, radiation monitoring, space exploration, and nuclear non-proliferation. Most of these applications need scintillating materials with high light yield, good energy resolution, fast time response, high detection efficiency, non-hygroscopic nature, can be grown in large volume single crystalline form, proportional light response, and low cost.
Thallium (Tl) ion is known to have very efficient luminescence in the widely used NaI:Tl, and CsI:Tl scintillators. Besides being an efficient luminescence center, Tl possesses a high density and effective number so that its presence in host material increases the density and effective atomic number of the scintillators. This research is based on the idea to incorporate heavy Tl ion in the host materials to discover and develop novel inorganic single crystal scintillators with excellent scintillation response.
Single crystal growth of the stable phases in LaCl3-TlCl, GdCl3-TlCl, and CaCl2-TlCl phase diagrams were grown by two zones vertical Bridgman techniques. These compounds include Tl2LaCl5, TlGd2Cl7, Tl2GdCl5, Tl3GdCl6, and TlCaCl3. Several melt-based techniques were studied for the compound synthesis of these materials and found the rotating melt technique to be the efficient one. It was found that the good quality single crystals of these materials can be grown with modified two zones Bridgman furnace. All these novel crystals possess high X- and γ-ray detection efficiency due to high effective atomic number and density which lies in the range of 67-74 and 4.4-5.4 g/cm, respectively. These scintillators have a high light yield of ~30,000-80,000 ph/MeV, a good energy resolution of ~3-6% in full width at half maximum (FWHM) at 662 keV γ-rays and fast decay time below 100 ns. Moreover, intrinsic Tl2LaCl5possesses good pulse shape discrimination for γ-rays and α-particles. These novel scintillators can be used in the future radiation detector design for applications in the various technological and industrial fields due to its excellent scintillation performance.

Thesis Advisor: Prof. Hongjoo Kim