2ND-GENERATION BEATWAVE EXPERIMENTS AT UCLA

The NEPTUNE Laboratory, under construction at UCLA, will be a user fac ility for exploring concepts useful for advanced accelerators. The pri mary programmatic goal for the laboratory is to inject extremely high- quality electron bunches into a laser-driven plasma beat wave accelera tor and explore ideas for extracting a high-quality Delta E/E < 0.1, e psilon < 10 pi mm mrad), high-energy (100 MeV) beam from a plasma stru cture operating at about 1 THz and about 3 GeV/m. The lab will combine an upgraded MARS CO2 laser and the state-of-the-art SATURNUS RF gun a nd linac, also undergoing an upgrade. The new MARS laser will be about 1 TW(100 J, 100 ps), up from 0.2 TW (70 J, 350 ps). This allows for d oubling the spot size of the laser beam and thereby quadrupling the in teraction length while still driving gradients of 3 GeV/m. The large d iameter of the accelerating structure relative to the injected electro n bunches (10:1 ratio) will minimize the deleterious effects of the ra dial dependence of the accelerating field and soften the radial focusi ng thus permitting, in principle, the extraction of a high-quality acc elerated beam. (C) 1998 Elsevier Science B.V. All rights reserved.