The establishment of reference radiation device in the range of (20 - 300) kV X-rays

For promoting the work that the air-kerma primary standard value be transferred, the reference radiation device is established in the range of (20-300) kV X-rays. Two low-energy reference radiation qualities 50 kV (a) and 50 kV (b) recommend by CCRI are established on the uniform radiation field. The distance from the source to the reference plane is 1 m. Half-value layer and homogeneity coefficient are measured by the fitting method. The difference with the recommended values is within 2%. Their spectrum distribution can be got by Monte Carlo simulation software EGSnrc and their average energies are calculated to be 33.3 keV and 28.1 keV respectively. (authors)