| Since the end of the 19 th century,Roentgen has discovered an unknown ray and named X-rays.X-ray applications have become more and more widely used in medical diagnostics,medical treatment,industrial nondestructive testing,radiation breeding,non-contact measurement,and high-energy physics research.In recent decades,the amount of ionizing radiation mainly used in China is mainly the amount of irradiation,and the air kerma energy as a new generation of ionizing radiation can replace the amount of irradiation in most cases.The comparison of the air kerma energy has also begun.National Institute of Metrology,China(NIM)has completed(60~250)KV X-ray air kerma benchmarks and(10~60)KV X-ray air kerma benchmarks.In 2017,NIM obtained the medium and low energy benchmark certificate.The molybdenum target X-ray reference was also compared to BIPM in April 2018.In recent years,breast cancer has developed into the first killer of serious threats to women's health.Among the various examination methods,mammography has greatly reduced the rate of missed early breast cancer,and thus reduced breast cancer mortality by 25%-30%.Improvements in inspection equipment can improve image quality and ability to examine early breast cancer.For most people,the density of breast tissue is small,and the image resolution and contrast formed by Mo target X-ray machine are higher;but for some breast tissue with large thickness and high density,in order to reduce the absorbed dose of patients,The W target is more suitable.The W target X-ray energy has a high wavelength and a short wavelength,and it is easier to penetrate a tissue having a high density,and can shorten the irradiation time by 1/5 to 2/3.However,its air kerma has not been successfully transmitted.In this paper,a tungsten target molybdenum filter X-ray radiation with a tube voltage of 23,25,28,30,35 KV was established in the low-energy X-ray reference radiation field of China Institute of Metrology.The additional filtration was 0.06 mm Mo.Its half-value layer measurement shows that the half-value layer is maintained at 0.346 to0.405 mm of aluminum.The effective energy is maintained at 15.4 to 16.4 keV,which is significantly higher than the molybdenum target X-rays excited by the same tube voltage.The measured radiation energy spectrum was measured,and the measurement results showed that the energy spectrum and the analog spectrum had a very high coincidencedegree,and the accuracy of the established radiation quality was further demonstrated.At60 cm away from the focal spot of the light pipe,the measurement of the radiation field using the finger type ionization chamber showed that the 95% effective radiation field diameter was 50 mm,which fully met the experimental requirements.The correction factor was measured for the newly processed molybdenum target ionization chamber and the low energy reference ionization chamber,and the fixed value work was completed.The two ionization chambers RC6M-9066 and 34069-000234 were scaled to verify the accuracy of the reference ionization chamber setup.The recurrence uncertainty of air kerma rate was controlled at 0.41%,and the scale factor uncertainty was 0.42% and0.43%,respectively. |
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