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The cargo scanner has been used to find the contraband interceptions and illegal objects in the large container at the airport and harbor. For the detection of these materials, a scintillator is used as a detection medium. The scintillation properties of CdWO4 (CWO) crystals have been studied to develop an X-ray scanner for a cargo container. The CWO crystal is composed of highly effective Z number materials, and it has a high density, therefore, a high detection efficiency for X-rays and γ-rays is expected. I selected various CWO crystals made in Russia (Novosibirsk) and China for comparison. The X-ray luminescence and the scintillation properties were studied with various sizes (4x4x30mm³, 4x7x30mm³ and 4x12x30mm³) of polished and unpolished crystals. The transmittance and X-ray emission spectrum of the CWO crystals were studied. The scintillation properties, such as the decay time, energy resolution and light yield, were measured and compared by using gamma excitation source. All samples exhibited similar decay times, with a value of 12 μs. The light yield and the energy resolution of the Russian samples were found significantly better than those of the Chinese samples. The proton response and radiation hardness of the CWO crystal were studied by using the 45-MeV proton beam from the MC-50 cyclotron at the KIRAMS (Korea Institute of Radiological and Medical Science). In addition, the response of the proto-type detector consisted of CWO scintillator and PIN photodiode were studied with the change of incident X-ray current using the charge integration module. All studies were carried out at Kyungpook National University (KNU) except the measurement of radiation hardness.
Thesis Advisor: Prof. Hongjoo Kim