The Research About Establishment And Application Of X-ray Reference Radiation Field

Since X-ray was discovered, it has become the focus of attention, it is widely used in material analysis, medical diagnosis, radiotherapy, safety inspection, nondestructive testing, and other fields of scientific research. Pointing at the application of the X-ray in the diagnosis, the thesis did a series of related research.A mammography X-ray reference radiation field has been established, including the X-ray tube, a diaphragm, and an optical platform, calibration platform, positioning systems, controllers and control software. There are two x-ray tubes in the system. According to the difference of the targets, they can be called as the molybdenum target and tungsten target. Two X-ray beams of the two X-ray tubes were measured and adjusted with two methods, namely, the finger ionization chamber and the matrix ionization chamber. The reference plane for the field was positioned at 600 mm from the radiation source, ensuring the beam diameter in the reference plane achieves 100 mm for all radiation qualities.According to IEC 61267 report and Key comparison BIPM.RI(1)-K7, four reference radiation quality were established, namely,25kV,28kV,30kV and 35kV. The reference plane for the field was positioned at 600 mm from the radiation source, with a reproducibility of 0.03 mm. In this position, according to the X-ray attenuation rule, the half-value layer was measured respectively about four radiating quality. The corresponding homogeneous coefficients were calculated, and the corresponding effective energy was fitted out. The tube voltage was measured respectively with intrusive and non-intrusive methods. In order to describe the tube voltage more accurately, the tube voltage of medical mammography were measured by non-intrusive methods.The method is based on diode probe and digital circuit. And the resistive volt ratio boxes were calibrated using the result. At the same time, the sampling data was processed by Gaussian distribution, excluded the data outside 3 ?. The tube voltage ripple was recalculated and compared with the defined value. The value of the mammography radiation field was determined by using RC6M ionization chamber. A new primary standard of air kerma was constructed at the NIM. Four radiation quality air kerma rates were obtained, and the barracoda dosimeter was calibrated.A new set of benchmark molybdenum target X-ray device was autonomously designed and built. The thesis established the molybdenum target X-ray 25 kV,28 kV,30 kV,35 kV specifications under radiation quality, and a series of experiments were designed and completed. The cylindrical ionization chamber is an important part of the reference device, in this paper, the ionization chamber leakage current, voltage saturation curve and long-term stability were studied. A set of ionization current measurement system is built, which is closely matched with the software and hardware, achieving the purpose of accurately measuring the ionization current.The completion of the above work, basically achieved the goals of the project acceptance index. The result laid the foundations for the molybdenum target X ray four norms of international comparison and the domestic breast value traceability.