Nath R, Schulz R J
Med Phys. 1977 Jan-Feb;4(1):36-41. doi: 10.1118/1.594299.
A sensitive and relatively simple method for obtaining an index of the spectral quality of high-energy x rays is presented. The method is based upon the use of photoactivation threshold detectors. Photonuclear reactions produce measurable amounts of radioactivity for radiation exposures of several thousand roentgens. Since the threshold energies for photonuclear reactions vary for different nuclei, the ratio of radioactivity induced in two appropriately selected foils is very sensitive to the x-ray spectrum. Photoactivation ratios (PAR) have been measured for 20-35-MV x rays using Co, Cu, Y, Zr, and Au activation foils. It is shown that the PAR method offers a sensitive and practical means for quality control of x-ray spectra, comparison of high-energy accelerators, and the measurement of variations of spectral quality control at different point in an irradiated volume.
本文介绍了一种灵敏且相对简单的获取高能X射线光谱质量指标的方法。该方法基于光激活阈值探测器的使用。光核反应在几千伦琴的辐射照射下会产生可测量的放射性。由于不同原子核的光核反应阈值能量不同，在两个适当选择的箔片中诱导的放射性比率对X射线光谱非常敏感。使用钴、铜、钇、锆和金激活箔测量了20 - 35兆伏X射线的光激活比率（PAR）。结果表明，PAR方法为X射线光谱的质量控制、高能加速器的比较以及辐照体积中不同点的光谱质量控制变化测量提供了一种灵敏且实用的手段。
