• Z.G. He, Q.K. Jia, X.E. Wang
  USTC/NSRL, Hefei, Anhui

A Photo-Cathode RF Gun is under development at NSRL. In this paper, the drive laser system is introduced and performance parameters are presented. We adopt a BNL type gun with laser illuminating the cathode at oblique incidence. To orrect 'time slew' and 'elliptical spot' problems arisen on the cathode, an adjustable optical transport line is designed.

• Q.K. Jia, H. Geng, H.T. Li
  USTC/NSRL, Hefei, Anhui

An easy-to-implement scheme called Enhanced High Gain Harmonic Generation has been proposed and shown to be able to significantly enhance the performance of traditional HGHG-FEL. In this paper we investigate the effects of the system parameters in EHGHG scheme, such as the electron energy tuning, the energy spread, the dispersive strength, amount of the phase shift, and the power of seed laser. The numerical results are presented, and shown that: the EHGHG scheme has acceptable the parameters tolerance requirements and is not more or even less sensitive to the system parameters than that of the existing scheme.

• Q.K. Jia
  USTC/NSRL, Hefei, Anhui

The enhancement of arbitrary odd harmonic field is analyzed for pure permanent magnet undulator. The two dimensional analytical formula of the magnetic field is given for a modified Harbch type undulator, in which the magnet blocks have different size. It is shown that the odd harmonic field can be enhanced by optimal the length ratio of the vertical magnetized magnet blocks and the horizontal magnetized magnet blocks, the 3rd harmonic field can exceeded 20% of the fundamental field and 7th harmonic field can exceeded 3 % of the fundamental field for magnet gap-period ratio equal to 0.1.