The NEPTUNE facility for 2nd generation advanced accelerator experiments

The NEPTUNE Laboratory, under construction at UCLA, will be a user facility for exploring concepts useful for advanced accelerators. The programmatic goal for the laboratory is to inject extremely high quality electron bunches into a laser-driven plasma beat wave accelerator (PBWA) and explore ideas for extracting a high quality ΔE/E<0.1, ε_n<10 π mm-mrad, high energy (100 MeV) beam from a plasma structure 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 and linac. The new MARS laser will be about 1 TW (1005, 100 ps), up from 0.2 TW (70 J, 350 ps). This allows for doubling the spot size at the IP and quadrupling the interaction length while still driving gradients of 3 GeV/m. The SATURNUS gun will be upgraded to the Brookhaven 1.6 cell design. A novel, multi-cell plane-wave transformer (PWT) RF gun is also under development. A sync-pumped, sub-ps dye laser is available to directly produce ultrashort electron pulses (1/5 of an accelerating bucket). Part of the research program will be devoted to studying pulse compression and phase-locking techniques at these ultrahigh frequencies and diagnosing microbunches generated by such structures. Finally, shaped electron pulses will be studied for the electron driven PWFA concept