Irradiation of Nd - Fe - B Permanent Magnets with APS Bending Magnet X - rays and 60 Co γ - rays

Introduction The Advanced Photon Source (APS), as well as other third-generation synchrotron light sources, uses permanent magnets in the insertion devices to produce x-rays for scientific research [1,2]. When placed in a high-energy storage ring, these permanent magnets are subjected to irradiation from synchrotron radiation, high-energy bremsstrahlung, and bremsstrahlung-produced photoneutrons. Previous investigations have exhibited varying degrees of degradation in the intensity of magnetization of these magnets [3] due to The APS specifically uses Nd-Fe-B permanent magnets in their insertion devices [2]. Although no detectable radiation-induced demagnetization has been observed in the APS insertion devices so far [12], partial demagnetization has been observed in at least one insertion device at the European Synchrotron Radiation Facility (ESRF) [4,6], where Nd-Fe-B permanent magnets are also used. LS-288 2 A growing concern for the APS insertion devices as well as the insertion devices of next-generation light sources, such as the Free Electron Laser (FEL) [13,14] where permanent magnets will also be used, resulted from the partial demagnetization observed at the ESRF. Next-generation light sources will by far exceed the third-generation sources in terms of brightness, coherence, beam power, and energy [14]. The brightness of radiation produced in such sources is expected to be several orders of magnitude higher than current, third-generation sources [15]. This increase in brightness from the enhanced synchrotron radiation would result in a greater absorbed dose to the insertion devices from synchrotron radiation scattering. Bremsstrahlung radiation will also be several orders of magnitude higher for future light sources and is expected to increase the absorbed doses to the insertion devices. The high power output of these next generation sources is expected to degrade the vacuum of the long straight sections many orders of magnitude. This vacuum degradation due to radiation desorption will increase the absorbed dose received by the insertion devices due to increased gas bremsstrahlung, as gas bremsstrahlung from the straight section increases linearly with pressure [16]. The longer straight section of approximately 50 meters will also account for an increase in bremsstrahlung. Larger beam bunches required for the single-pass operation of linear accelerators used in next-generation sources again will contribute to an increase in bremsstrahlung, as measurements at the APS showed that bremsstrahlung increases as the square of the transverse bunch profiles [16]. Smaller vacuum chambers proposed for use in the next-generation sources may also contribute to the absorbed doses due to bremsstrahlung depending on the beam location inside …