RF System Modeling And Research On Algorithm Of Digital Low Level RF System Of Soft X-ray Free Electron Lasers

Free electron laser (XFEL) which uses a beam of electrons with high qualityhigh relativity as its working medium, and then generated by wave periodic changesin the magnetic field is a new light source with a high brightness, short pulse,performance can be tuned, time and space coherence. These characteristics make thefree electron laser has a wide application in many fields of scientific research,especially in material science and photochemistry, information science, environmentalscience and life science, internationally known as the fourth generation light sourcehas been widely development. In this context, a1GeV soft X-ray FEL facility(SXFEL) will be built close to Shanghai Synchrotron Radiation Facility (SSRF). Afterthe commissioning of SXFEL, all the critical technology issues should be test andpredominated. The SXFEL is mainly used as the pre research of hard X-ray freeelectron laser facility in China.For the requirement of SXFEL facility, RF system with high performance, highgradient accelerating structure and short period undulator should be issued. In thedissertation, the detail background of the low level RF system is reviewed, and thedesign proposal of the LLRF system is introduced.In the dissertation, the detail design and research of RF low level system arediscussed. A design scheme of high frequency low level control system of soft X rayfree electron laser was determined and the design of the low level control system iscompleted through detailed investigation.In the dissertation, mathematical models of the high frequency device are derivedfrom the basis accelerator physics and microwave theory. The influence ripple of themodulator on klystron is analyzed. The model of SLED is analyzed in detail. Theeffects from the parameters variations are analyzed. Through theoretical analyses, theprecision of the parameters are Preliminary determination.This paper designs the algorithm of IQ modulation, digital PI regulator, digitalphase shifter, digital FIR filter, CRODIC, etc. The common used math functions are packaged together as a universal library, so it can be shared with each other.Combined with the requirement of Shanghai soft X-ray free electron laser, lowlevel RF system based on MTCA.4was studied. The prototype of LLRF based onMTCA.4was built and tested in laboratory.