The Low-Field NMR System’s Application And Research

Since Purcell and Bloch found the nuclear magnetic resonance (NMR) in1946, more and more attention has been paid to NMR and NMR are gradually evolved into a comprehensive discipline that has a complete theory and practice after60-year development. Through the continuous efforts of scientists, NMR has been applied into the microcosmic field and achieved fruitful progress in exploring the structure and properties of substances direction. But the most research has been devoted to the high field spectrometer which is large, high precision. For some low field spectrometer suitable for civil did not get much attention. The purpose of this research is to study a small nuclear magnetic resonance device that is suitable for low field environment and can be used in the field of hyperpolarized gas monitoring and proton monitoring etc.This thesis describes the historical development of NMR, analyses various kinds of existing domestic and foreign research status of low field NMR. In addition, it presents the details of the basic theoretical knowledge of NMR, a full description of NMR using classical vector model, and analysis of the method for measuring and analyzing of NMR relaxation.This thesis manly focuses on the design of a low field NMR system. Firstly, it introduces the whole structure of the low field NMR system, analyzes the working principle of power amplifier,NMR probe,duplexer,pre-amplifier circuit and other parts of the hardware circuit in the magnetic resonance system. Secondly, it presents the actual circuit, experiments of each part of hardware circuit, and further improvement of the overall performance of the circuit after the comparison of the analysis and simulation results. Finally, it introduces the basic composition and design process of the data acquisition subsystem. In addition, software programming of the low field NMR system for data acquisition is completed. Combining with simulation test, the program has been improved.After testing the developed low field NMR system, the results show that the indicators are in line with the experimental requirements, thus a good experimental effect is achieved. At the same time, analysis of the difference between the expected and the experimental results is implemented. The thesis ends up with some suggestions about subsequent experimental work.