Magnetization measurement scheme for radiation demagnetization evaluation of permanent magnets

Fuwa, Yasuhiro   ; Kuriyama, Yasutoshi*; Iwashita, Yoshihisa*

Radiation demagnetization by neutron irradiation has been measured using the Kyoto University research reactor to evaluate the radiation resistance of permanent magnet materials used for beam optics of accelerators. In the demagnetization evaluation, it is essential to measure the magnetization before and after neutron irradiation accurately, but in the case of measuring the magnetic field using a Hall probe, the displacement of the measured value due to the probe position is relatively large and causes errors in the demagnetization evaluation. In order to realize magnetization measurement with less systematic error, we have developed a method to measure the magnitude of magnetization from the induced electromotive force on coils by rotating the magnet near the coil. By adopting this rotating-magnet method for magnetization measurements, the error of the measured value can be reduced to 0.1%, and the measurement accuracy of radiation demagnetization has been improved.