Laser Extraction of an Electron Beam from a Modified Elongated Betatron Accelerator

The Modified Elongated Betatron Accelerator (MEBA) that was developed at UCI has demonstrated injection, trapping and confinement of about 1012 electrons. The electrons have been accelerated to about 1 MeV. They occupy an annular region 80 cm long with a 6 cm radius and a thickness of about 0.5 cm. We propose to contract this annular beam from 80 cm to a few centimeters by moving the magnetic mirrors. Then the beam will be extracted by means of a laser-initiated channel to guide the beam across the magnetic field. This will be accomplished with a gas puff valve to inject benzene gas and a KrF laser. In this paper, we describe the necessary modifications of the accelerator to accomplish laser extraction of the beam.