Radiation levels experienced by the insertion devices of the third-generation synchrotron radiation sources

Third-generation synchrotron radiation sources like the Advanced Photon Source (APS) use insertion devices made of Nd-Fe-B permanent magnets to produce X-rays for scientific research. The concern of radiation-induced demagnetisation of these insertion devices spurred a-project aimed to measure and analyse the radiation levels experienced by these insertion devices during the operation of synchrotron radiation sources. The project required a reliable photon high-dose dosimetry technique capable of measuring high integrated dose levels during one operational cycle. Radiachromic dosimeters were considered for this purpose. In collaboration with the National Institute of Standards and Technology (NIST) these dosimeters were tested, calibrated and used at the Advanced Photon Source. Prior to each run radiachromic dosimeters are placed on the upstream and downstream edges of the 2.5 m long insertion devices. Following each operational cycle these dosimeters are retrieved from the storage ring and optical density changes are analysed. The measurements are compared with previous estimates. The results show that the previous predictions grossly underestimate the radiation levels received by the insertion devices.