Effects of undulator harmonic field enhancement on electron beam spontaneous radiation

Making good use of harmonic radiation field is one of the most straight forward methods to generate radiation at short wavelength. The enhancement of undulator harmonic magnetic field could increase the radiation intensity at the harmonic wavelength. A modified Halbach undulator was analyzed, and its magnetic contents were computed. The analysis shows that the modified Halbach undulator could improve the third harmonic magnetic field to 25% of the fundamental. The effect of the enhanced harmonic magnetic field on the spontaneous radiation spectrum was analyzed using the electron beam parameters in Hefei Light Source. The analysis shows that when the third harmonic magnetic field is improved to 25% of the fundamental in the modified Halbach undulator, the photon flux at the third harmonic o