Development of 30 T Repeating Pulsed Field

研制了一种用于高磁场中子衍射实验的重复脉冲场系统。使用本系统可产生高达30 T的磁场。25t以上的磁场还没有通过超导磁体获得过。因此，目前的场强是世界上中子衍射的最高场强。磁铁采用三层苦磁体。三层结构的使用改善了相邻层之间的电气和机械接触，实现了较长的磁铁寿命。作为25 T以上中子衍射实验的第一个测试，我们研究了三角形晶格反铁磁体CuFeO2的超磁相变。在20 t左右，磁性结构由不对称结构向对称结构转变。在Dy Cu中进行了中子衍射实验，研究了超磁性跃迁的性质。本文的研究结果证实了利用重复脉冲磁场系统在20 T以上的超高场中进行中子衍射实验的可行性。

A repeating pulsed field system has been developed for the neutron diffraction experiments in high magnetic fields. Magnetic fields as high as 30 T can be generated by using the present system. Magnetic fields above 25 T have not been obtained by way of a superconducting magnet. Therefore, the present field intensity is the highest field for neutron diffraction in the world. As the magnet, 3-layer Bitter type magnet is used. The use of the 3-layer structure improves the electric and mechanical contacts between the adjacent layers and the loge life-time of magnet is achieved.As the first test of the neutron diffraction experiments above 25 T, we have investigated the metamagnetic phase transition in a triangular lattice anti-ferromagnet CuFeO2. The change of the magnetic structure from the incommensurate to the commensurate structure was found around 20 T. The neutron diffraction experiments in Dy Cu was also made and the nature of metamagentic transition was investigated. The present results have established the feasibility of the neutron diffraction experiments in very high fields above 20 T by using a repeating pulsed magnetic field system.