At present,the international research on the X ray air kinetic energy standard is only up to 400 kV,however for higher energy X ray, the corresponding standard has not been established. In this paper,we analyze the uncertainty of the air kinetic energy of self derived 250~450 kV X ray,and get the uncertainties of physical constants, effective measurement volume, positioning distance, current measurement,temperature,air pressure and correction factor respectively. What's more,we also get the uncertainty of the relative synthetic standard of the 250~450 kV X-ray air kerma is 0.31% and the uncertainty of development is 0.62% (k=2). The leading two values of the source of uncertainty are the ionization work and correction factor,which are meeting the requirements of the reappearance of X ray air kinetic energy.%目前,国际上对X射线空气比释动能基准的研究最高只达到400 kV,对于更高能量的X射线尚未建立相应基准.本文对自建立的250~450 kV X射线空气比释动能结果的不确定度进行了分析,分别得到了物理常数、有效测量体积、定位距离、电流测量、温度、气压、修正因子的不确定度.最终得到250~450 kV X射线空气比释动能结果的相对合成标准不确定度为0.31%,扩展不确定度为0.62%(k=2),其中不确定度来源中最大的2个量为电离功和修正因子,满足X射线空气比释动能复现的要求.
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