Parameter optimizations for vacuum laser acceleration at ATF/BNL

The major difficulty in using laser fields in the vacuum to accelerate the electrons is that its phase velocity of the electric field for accelerated electrons is faster than the speed of light when the electrons travel over long distance larger than 3 times the laser Rayleigh length. Its acceleration length can be defined with simple optics. In order to get the higher energy gain at ATF/BNL, the laser parameters and related electron beam are analytically investigated. The experiment specifics require an extremely small electron beam size. Achieving and measuring such small beams present a real challenge. The vacuum laser acceleration experiment will be conducted at the Brookhaven Accelerator Test Facility (ATF), using its high-power CO2 laser and tiny focused electron beam. An energy gain of the order of 0.5 MeV is expected.