Development of the alternate entry port for the ATF

We discuss a second entry port for the Accelerator Test Facility (ATF) injection system at Brookhaven National Laboratory, which consists of a photocathode rf gun and a straight-ahead beamline directly into the 50 MeV linac. The proposed second entry port should improve the beam quality and lower the emittance needed for FEL (Free Electron Laser), and laser-acceleration experiments. A discussion on the laser driven high brightness photoelectrons through the primary entry port (a low energy 180 degrees achromatic double bend transport line) now in operation, and a beam analysis for the proposed secondary port is also given