Radiation dose measurements of the insertion devices

The Advanced Photon Source (APS) uses Nd-Fe-B permanent magnets in the insertion devices to produce x-rays for scientific research. Earlier investigations have exhibited varying degrees of demagnetization of these magnets due to irradiation from electron beams, 60Co γ-rays, and high-energy neutrons. Although no detectable radiation-induced demagnetization has been observed in the APS insertion devices so far, partial demagnetization has been observed in at lest one insertion device at the European Synchrotron Radiation Facility (ESRF), where Nd-Fe-B permanent magnets are also used. A growing concern for the APS insertion devices, as well as the permanent magnets that will be used in next generation high-power light sources, like the FEL, resulted from the partial demagnetization observed in the ESRF devices. This concern in relation to radiation-induced demagnetization spurred a long-term project aimed to measure and analyze the total absorbed doses received by the APS insertion devices. The project required a reliable photon high dose dosimetry technique capable of measuring absorbed doses greater than 106 rad, which was not readily available at the APS. Through a collaboration with the National Institute of Standards and Technology (NIST), one such technique using radiachromic films was considered, tested, and calibrated at the APS. This consequently led to the implementation of radiachromic films as the technique of choice for measuring the total absorbed doses received by the insertion devices for each of the APS runs