| Short period undulators are of significant interest to synchrotron radiation society for their capabilities to produce photons with higher energies as well as they allow more periods to be hosted within the same length.Permanent magnet(PM)based short period undulator is the most promising scheme.As the period length goes shorter,the field quality degrades due to the imperfections in the PM blocks,which can not be well compensated by traditional field correction methods.The most prone ones of the field quality issues are the large variation in the field integral errors and the large initial shim distances.This dissertation focus on the development of new effective correction methods that lead to better field qualities of short period PM based undulators.The first chapter described the field quality issues caused by the imperfections in PM blocks,the existing correction methods,and their limitations.The main structure and the highlights of this dissertation were also listed in this chapter.The second chapter presented the basic knowledge of PM-based undulators,including their designs,the effects of the field errors as well as the measurements of these errors.A new method for sorting the PM blocks of hybrid undulator was presented in the third chapter.This method took the local imperfections of PM blocks into consideration with the help of an innovative magnetic field mapping device whose calibration was emphasized.In the fourth chapter,a new method for correcting the field integral error of hybrid undulators by the fine machining of soft iron poles are presented.The implementations of this method on two newly developed undulators lead to field integral error below 20 μT · m.The last chapter summarized this dissertation.The works in this dissertation laid a technical foundation for the development of PM-based short period undulators. |
