Development of 30 T Repeating Pulsed Field

研制了一套用于强磁场中子绕射实验的重复脉冲场系统。使用本系统可以产生高达30T的磁场。25T以上的磁场不是通过超导磁体获得的。因此，目前的场强是世界上中子衍射场最高的。磁体采用三层Bit型磁体。这种三层结构的使用改善了相邻层之间的电接触和机械接触，提高了磁体的寿命。作为25T以上中子衍射实验的首次测试，我们研究了三角形晶格反铁磁体CuFeO2的变磁相变。在20T附近发现了磁结构从非公度结构到公度结构的变化，还进行了Dy-Cu的中子衍射实验，并对变质转变的性质进行了探讨。这些结果为利用重复脉冲磁场系统在20T以上的超高场中进行中子衍射实验奠定了基础。

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.