同步辐射硬X射线光子通量的绝对测量

Absolute measurement of photon flux for synchrotron radiation hard X-rays

在北京同步辐射光源上使用自由空气电离室绝对测量了同步辐射硬X射线光子通量。通过自由空气电离室复现空气比释动能率量值,根据在电离辐射量及其单位中定义的空气比释动能与注量及通量的关系,定量得到了光子通量。由于在测量期间,光子通量随时间变化,而测量需要一定的时间,因此,研究了配套的在线通量监测系统,监测带来的不确定度为0.03%。通过测量空气衰减修正因子及复合损失修正因子,结合在线通量监测,在能量为15keV的同步辐射X射线上用自由空气电离室复现了空气比释动能率。在实际实验条件下复现的空气比释动能率为0.239Gy/s,从而得到同步辐射X射线的光子通量为5.28×10~9 photons/s,相对标准不确定度为0.68%。

The photon flux of the synchrotron radiation hard X rays was measured in Beijing Synchrotron Radiation Facility(BSRF)using a free air ionization chamber.Absolute air kerma can be obtained with the free air ionization chamber.The photon flux was calculated based on the relation between air kerma and flux in the fundamental quantities and units for ionizing radiation.Because the photon flux changes over time during the measurement,an online monitoring system was applied,and the uncertainty of which is0.03%.The air attenuation correction factor and ion recombination correction factor were measured at15keV synchrotron radiation X rays.The measurement results show that the absolute air kerma rate at15keV synchrotron radiation X rays is0.239Gy/s,accordingly,the photon flux of the source is5.28×109photons/s,the relative uncertainty is0.68%.