Study On The Power Supply And Magnet Of A Pulsed Magnetic Field System And Realization Of Pulsed Flattop Fields

Magnetic fields can directly affect the behavior of electrons and some particles of this kind, it is an important and basic research tool for modern scientific research. With the development of the scientific research, the demand of the strength of the field becomes higher and higher, which is mainly due to the higher field can induces more new scientific phenomenon.High magnetic field refers to the field that the strength is higher than that of commercial superconducting magnets. High magnetic field is always divided into two kinds:continuous high magnetic field (CHMF) and pulsed high magnetic field (PHMF). The field of CHMF is steady and continuous, while the field of PHMF is just a pulse, the field is changing every seconds and not continuous. This dissertation will focus on the construction and problems of PHMF.A PHMF laboratory always has three parts:the pulsed power supplies, the magnets and scientific experimental infrastructure. The scientific experimental infrastructure provides experimental conditions (like low temperature, Vacuum and so on) and measuring the signal of the sample. But the part of scientific experimental infrastructure will not be discussed in this paper.There are three kinds of power supplies for PHMF:capacitor banks, pulsed generators and inductors of storing energy. The most important two kinds of those are capacitor banks and pulsed generators. The structure of capacitor banks is simple, the construction, the operation and maintain are easy; the pulsed generator power supply has very high energy storage density, and the output voltage can be controlled according to the actual requirement. The power supply system of the PHMF will be discussed in chapter 2.Magnets are the core of the pulsed field facility. There are magnetic field, thermal field and stress field in a magnet, and those three fields interact on one another. The current of the magnets generates magnetic field, then the Lorentz Force will act on the winding of the magnets, the material will deforms and lead to the change of the stress field. The current will also generate heat in the magnet, which induces the rise of the temperature and the increase of the magnet resistance. On the other side, the resistance will affect the heating power and the temperature. So the magnetic field deeply interacts with the thermal field. The thermal field also interacts with the stress field, such as heat stress. The physical process in pulsed magnets is very complicated. The physical process and the basic electromagnetic parameters of magnets will be discussed in chapter 3.The CHMF generates steady and continuous field and the PHMF generates higher field. Both high stability and high strength of the field are demanded for some scientific experiments such as NMR and the measurement of specific heat. To satisfy these kinds of demands, a pulsed flattop field is proposed. It is a kind of field that is in between the CHMF and the PHMF. It provides a steady field for a time and has higher strength than the CHMF. This paper will discuss the implement method for realizing the pulsed flattop field. This paper designed a dual coils magnet to realize flattop field. The inner coil is powered by capacitor bank to provide a regular pulse field waveform, while the outer coil is energized by a controllable pulsed generator which starts to work when the field of the inner coils falls. The outer coil works to keep the sum of field at hole of the magnet constant. When reaching the desired duration, the pulsed power supply works inverse to take back the energy of the outer coil, then field falls quickly. Chapter 4 will discuss the whole scheme and the optimization of the magnet considering the power supplies. Chapter 5 introduces the manufacture process of the magnet and the test results of the magnets.