Study on the Standard Surface Source of Gamma-ray in High Energy Region Based on ²²⁶Ra

The calibration of gamma-ray detection efficiency is the basic work of radioactivity measurement. Because of the scarcity of high-energy gamma-ray standard source, it is difficult to calibrate the high-energy gamma-ray detection efficiency. Based on long-lived radionuclide ²²⁶Ra and its long-term decay equilibrium radioactive daughter ²¹⁴Pb and ²¹⁴Bi, a standard surface source containing high-energy region gamma rays was developed. The energy range can cover 186 keV-2448 keV. The sealed planar source was prepared with ²²⁶Ra solution. By improving the structure of the source box, the effect of vertical spatial distribution on the accuracy of the source was significantly reduced. The activity of each gamma ray is calibrated by the standard device of the metering station,its stability and accuracy are tested. The results of tracking measurement for 30 days in succession show that the stability of each gamma ray counting rate is better than 1.5%. The efficiency curve of the calibration of the planar source is consistent with that of the ¹⁵²Eu standard source within 2%. The results show that the ²²⁶Ra surface source is stable, reliable and accurate. The surface source can be used for a long time, avoiding the cumbersome process of preparing ²⁴Na and other short-life standard source in high energy gamma ray detection efficiency calibration.