Monte Carlo Study in Radiation Damage Experiments of Permanent Magnets by High Energy Electrons

The demagnetization of permanent magnets used in the insertion device, becomes one of the most important issues of the next generation light sources. The demagnetization experiment has been carried out at the electron linac of Pohang Light Source. To find out the mechanism of radiation damage to the magnet, the radiation field around and inside the target and magnet in the experiment is investigated with Monte Carlo code FLUKA (2005 version). The energy spectra of photons and neutrons around the target and magnet are derived and analyzed The 3-dimensional dose distributions in the target and magnet due to 2 GeV incident electrons and secondary particles are also calculated. The calculated results under different target conditions (Cu, Ta target or no target) are compared. Some important parameters such as dose and 1 MeV equivalent fluence are summarized. Finally the demagnetization of the magnet due to radiation at high energy accelerator is discussed