Magnetic flux loss in rare-earth magnets irradiated with 200 MeV protons

• Published in: Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms Beam interactions with materials and atoms, 2001-10, Vol.183 (3), p.323-328
• Main Authors: Ito, Yoshifumi, Yasuda, Keisuke, Ishigami, Ryoya, Hatori, Satoshi, Okada, Osami, Ohashi, Ken, Tanaka, Shintarou
• Format: Article
• Language: English
• Subjects: 200 MeV proton beam; Nd–Fe–B magnet; Radiation-induced damage; Rare-earth permanent magnet; Sm–Co magnet; Wakasa-wan multi-purpose accelerator with synchrotron and tandam (W-MAST)
• ISSN: 0168-583X; 1872-9584
• DOI: 10.1016/S0168-583X(01)00725-X

The effects of 200 MeV proton irradiation on the magnetic flux of Nd–Fe–B and Sm–Co magnets have been investigated over the dose range from ∼10 2 Gray to ∼2×10 5 Gray. Nd–Fe–B magnets with coercive force H cj 1.15 MA/m and 2.5 MA/m were used as samples, where their permeance coefficient P c was 0.5∼2.0. The magnetic flux of Nd–Fe–B magnets decreased as the proton dose increased, while the flux of Sm–Co magnet did not change. The relation between the flux loss Δ Φ of Nd–Fe–B magnets and the absorbed dose D was expressed as Δ Φ=− ηlog D+const., where value η was 39±3% with D in Gray. The absorbed dose D 20, which caused the flux loss of 20%, was 5.1×10 2 Gray for P c=0.5,2.0×10 3 Gray for P c=1.0, and 6.8×10 3 Gray for P c=2.0 in case of Nd–Fe–B magnets with H cj=1.15 MA/m. The dose D 20 was 2.3×10 4 Gray for P c=0.5, and 2.9×10 5 Gray for P c=2.0 in case of Ne–Fe–B magnets with H cj=2.5 MA/m. Increase of both of permeance coefficient and coercive force led to the enhancement of the resistance to the radiation-induced damage.