| Summary: | 碩士 === 元培醫事科技大學 === 醫學影像暨放射技術系碩士班 === 107 === This study used gamma ray to illuminate the neutron-activated niobium, which illumination will turn 90 degrees to produce a coherent source. The goal is to develop a laser source that can be used in future phase contrast imaging systems that are miniaturized, or for other industrial applications.
According to patent number US20170115431A1, the invention initially verified that the gamma source can be turned 90 degrees, and the high purity germanium detector (HPGe) is used to resolve the energy spectrum and perform counting analysis. In this experiment, niobium with a purity of 99.99% was used, its size was 3cm × 1.5cm × 1mm, niobium was irradiated by THOR neutrons in Tsinghua University for 4 hours, and the irradiation power was 1.5W. A sequence of experimental designs is then performed.
The 5 millicurie 137Cs source is directed to the niobium, and a multichannel analyzer (MCA) is used to connect the high-purity detector to measure signal analysis, and is used with the MAESTRO computer software. Measure the difference of refraction of γ source with different parameters, change the direction of γ source, adjust the crystal lattice parameters, and complete a series of design experiments.
According to the long-term experimental measurement, the signal is quite obvious. There are seven obvious up and down oscillations, and there is Rayleigh scattering. In this short-term experiment, the measured signal is weak, and the Rayleigh radiation phenomenon is not obvious. The weaker signal may come from accumulated noise. In the future, the cutting size, the time of neutron irradiation, the time and method of annealing, and the like will be continuously improved.
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