Study on beam quality of CW photoinjector based DC gun

Electron beam quality is very important in the highaveragepower FEL. According to the characters of CAEP highaveragepower FEL, CW Photoinjector Based DC Gun is proposed in the paper. The beam emittance growth is also investigated under the condition that the beam distribution on the cathode is of Gauss's distribution. The beam emittance growth is mainly due to the space charge effect when the electron beam is accelerated and drifts after acceleration, so the field strength and the voltage are both very important to the injector. With the novel structure of the electrostatic acceleration, the field strength is more than 10MV/m, and the voltage is more than 1MV. After the beam simulation by PARMELA code, 5mm.mrad of the normalized beam emittance (rms) is acquired when the beam charge