平顶脉冲强磁场技术及其应用

Flat-Top Pulsed High Magnetic Field Technology and Its Application

平顶脉冲磁场(FTPMF)是指峰值磁场能持续稳定一段时间的特殊强磁场,兼具脉冲磁场高场强和稳态磁场高稳定度的双重优点,在前沿基础科学研究和工程技术领域中具有重要应用价值。该文根据飞轮储能脉冲发电机、电容器、蓄电池在功率、容量、输出电压等方面的特点,综述了FTPMF的产生及其高精度调控方法,介绍了改善FTPMF的稳定度、平顶时间等参数指标的最新技术进展。分析了FTPMF对改善核磁共振(NMR)性能和在测量材料物性中的关键作用,结合国家脉冲强磁场科学中心工作,给出了铌金属单质^(93)Nb在22T下的NMR测量、自旋二聚体Ba_(3)Mn_(2)O_(8)在64T下的比热测量、以及电荷密度波材料Li_(0.9)Mo_(6)O_(17)在30T下的非线性I-V测量应用情况。最后,对发展FTPMF需要的电源系统协同供电、小型化与模块化、脉冲磁体材料、寿命及其状态监测等技术,以及FTPMF在脉冲场回旋管太赫兹波源上的应用等进行了展望。

Flat-top pulsed magnetic field(FTPMF)is a kind of peculiar high magnetic fields where the peak field remains nearly unchanged within a finite duration time.Due to the advantages of its high field strength and high stability,it offers great opportunities to not only frontier fundamental science but also advanced technology.This paper summarizes recent progresses on generation of the FTPMF and high precision control of the flat-top parameters(stability and duration)by utilizing different power supplies such as flywheel energy storage pulse generator,capacitor bank and battery.We also introduce the key roles of FTPMF to improve the nuclear magnetic resonance(NMR)and physical property measurements.Several experimental results conducted at the Wuhan National High Magnetic Field Center are reported.These include the NMR measurement of ^(93)Nb single crystal at 22T,specific heat of a spin dimer system Ba_(3)Mn_(2)O_(8) at 64T,as well as the nonlinear I-V characteristic measurement of the charge-density-wave compound Li_(0.9)Mo_(6)O_(17) in a field up to 30T.Finally,we discuss the cooperative power supply(miniaturization and modularization)and the material performance of the pulsed magnet.The application of FTPMF in pulsed field gyrotron terahertz source is also prospected.