Effects of variation of the laser pulse width on the laser induced photoelectrons

The effects of the variation of the Laser pulse width on the laser induced photoelectrons, from the BNL gun is presented, including the variation in the emittance of the beam, which is crucial to the operation of a Free Electron Laser (FEL). The radio-frequency (RF) electron gun with a photocathode in the end wall of an RF cavity is excited by a laser pulse that is synchronized with the RF, is powered by a conventional type SLAC klystron, and is designed to produce a low emittance beam of 4.65 MeV at the gun exit with the field gradient of 100 MV/m on the Cathode.