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UBC Theses and Dissertations

A single crystal sodium iodide scintillation spectrometer for the investigation of gamma-ray spectra Azuma, Richard Ernest


A single crystal sodium iodide spectrometer has been developed for the investigation of gamma-ray spectra. The spectrometer was tested with the gamma-rays from the sources Eu¹⁵⁵,RaD, Na²², Zn⁶⁵, Co⁶⁰, and RdTh. The spectra from these sources have been obtained by analyzing the pulse height distribution from the scintillation counter with a single channel differential discriminator. A crystal mounting technique is described in which the crystals are mounted dry with a layer of magnesium oxide powder surrounding them to provide diffuse reflecting surfaces. With mountings of this type, 7% energy resolution has been achieved for gamma-ray energies of approximately 1 MeV. The expected pulse height distributions have been calculated and compared with the experimental distributions. The effect of multiple scattering events on the shape of the distributions is discussed,2and the effect of crystal dimensions on the resolution has been studied. It has been found that for the energy region 0.5 to 2.5 MeV the best resolution is obtained with small crystals. A search has been made for the presence of low energy gamma-rays in the decay of tritium, and it was found that within the accuracy of the experiment no gamma-rays were present. A preliminary report is presented on the investigation of possible scintillation produced in air by alpha particles. The effect has been shown to exist but no systematic study has been made.

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