The laser-plasma-accelerator-driven free electron laser project at the BELLA Center

At LBNL's BELLA Center, we have established a new facility dedicated to driving incoherent and coherent undulator radiation by electron beams produced in a laser plasma accelerator (LPA). A dedicated 100-TW class 5Hz laser system is coupled to a mm-scale LPA, followed by state-of-the-art electron beam transport, phase-space manipulation, diagnostics, and a 4-meter-long undulator. The viability of a compact coherent undulator-based light source [the free electron laser (FEL)], operational in the soft X-ray regime, hinges on the ability of the LPA to produce sufficiently bright electron beams and maintain this quality during transport. Intrinsic mrad-scale divergence, %-level energy spread, and fluctuations in beam energy, make this a challenging task. In this presentation we will present our approach, including improved laser stability, robust down-ramp injection in the LPA, compact active plasma lens technology for compact transport, a chicane for slice energy spread reduction, and the strong-focusing VISA undulator for enhanced beam-radiation interaction. Both simulations and experimental results will be presented.