Abstract
Over the last few years, the insertion devices played a key role in the development of synchrotron light sources. The applications on the free electron lasers and the third generation storage rings are getting demanding of the undulator with long length and small gaps. Such applications increase the loading and difficulty of the magnetic field measurement. Other than the existing Hall probe and coil methods used in the society of accelerator, several laboratories tried to conceive a wire- based system lately so as to speed up the magnetic field measurement on the small-gap insertion devices or long ones for efficient magnetic tuning. The pulsed wire method (PWM) is one of the candidates for these purposes. In spite of the easy setup of the system of PWM, the application limitation of this method has been raised. Generally the thin wires were used and only the short magnets were measured to reduce the dispersion effect due to the stiffness of the wires. Nevertheless, a lot of spurious signals on the string wave distorting of the real field signals were still commonly observed. In this thesis the author clarified the effects from wire imperfection and dispersion of string wave, which are deemed to the main sources of the distortion and limitations. For improvement, a strategy using thick wire instead to average out the imperfection was proposed, followed by canceling the dispersion and tracing back the normal field signal by using the fast Fourier transform calculation with the knowledge of digital signal process (DSP). The author studied a test PWM system over two prototype insertion devices of National Synchrotron Radiation Research Center (NSRRC). Detailed study showed that this method will be reliable and useful in precise measurement. The fidelity is quite close to Hall probe measurement and even outweighs it in integral field aspects. Furthermore, the study reflects that the physical and mathematical models of string wave need more efforts to explore.