Experimental Study on Flux Trapping and Flux Jump on Pulsed-Field Magnetization Process for Mg-B Trapped-Field Magnet
Résumé
MgB2 bulk materials used as quasi permanent magnets are characterized as its uniform field trapping property originated homogeneous microstructure of simple metallic compound. Beautiful conical shape of trapped field distribution would suggest us to utilize it to compact and stable magnets for practical industries. The only and crucial drawback is its thermal instability which causes sudden dissipation of trapped flux called “flux jump”, which is attributed to the poor specific heat of the material which would be utilized at low temperature less than 20 K. The authors carried on the successive PFM experiments with use of 15 K cryocooler, and precisely investigated various flux jump phenomena in detail. The motions of flux invasion are classified as three modes called “no flux flow (NFF)”, “fast flux flow (FFF)”, and “flux jump (FJ)” regions. The authors clarified that the introduction of metallic inclusion by adding Ti are effective to expand the NFF region to high applied field and to prevent the flux jump to happen.