| Summary: | 碩士 === 國立清華大學 === 電機工程學系 === 104 === With recent advances in the technology of radiation therapy, the application of radiation therapy for cancer treatment increases gradually. However, if the dose of radiation doesn’t meet the standard, it will be harmful. Many hospitals are equipped with instruments monitoring the dose of radiation. Wherein the dose monitoring method is mainly by detecting the current formed by the radiation induced charged particles which are collected the ionization chamber’s electrode plates, and then calculating the dose by the relevant formulas of the ionization chamber.
Since the measuring instrument of the Institute of Nuclear Energy Research (INER) is currently a current integrator for the main structure, and the price and efficiency of the instrument are more expensive and poorer; therefore, the main purpose of this thesis is to develop a pico-ampere order measuring prototype for radiation dose monitoring application which is based on ADC and TIA in order to reduce the development cost of the instrument and measurement time.
The basic core structure of this system is the development board MSP430F5438 produced by Texas Instruments (TI). The resolution of its ADC is 12 bits, and we use 20MΩ and 1GΩ high-precision resistors to go with the TIA IC. With the above architecture, our system is able to measure the current from 50nA to 4pA with the error rate less than 2% between 50nA and 0.1nA and less than 5% between 0.1nA and 4pA. We also use the other ports and functions of the development board to realize other functions which are important and helpful to a measurement instrument, including the screen display, key operation and self-test, etc. In addition to the above features, our cost is much lower than the PTW DIAMENTOR M4-KDK produced by Germany after we package and test our development board and circuit. Simultaneously, our prototype is also easier to operate, has smaller size, lighter weight and spends less measure time than the DIAMENTOR M4-KDK. It is believed that our prototype will be able to replace the more expensive instruments and become the mainstream instrument on the market once passing the test of the Electromagnetic Compatibility (EMC) and Electromagnetic Interference (EMI), and complying with the IEC60580 standards.
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