Compact free electron laser (FEL) technology enabled by plasma-based accelerators is rapidly maturing with several milestone demonstrations in the last 2-3 years. Still, critical work is needed to bridge the gap from proof of concept experiments to reliable operation of plasma-based FELs. At the BELLA Center, we have a laser plasma accelerator (LPA) beamline equipped with an electron beam transport section that culminates in a 4m long, strong focusing undulator. This undulator system with 16 embedded FODO cells, represents a comparable proxy to many undulator systems used at XFEL beamlines. Notably, the presence of distributed focusing imposes tight requirements on both transverse matching and alignment of the beam through the undulator in order to enable FEL lasing. Recent efforts have demonstrated quasi matched propagation of the LPA beam in the undulator. Additionally, through control of the launch trajectory into the undulator coherent enhancement of the undulator radiation can be triggered, a strong indication of FEL gain. Recent results and future plans are discussed.

Owing to strong 10-100 GV/m accelerator gradients, Laser Plasma Accelerators (LPAs) have the capability to generate high-brightness and high-energy electron beams in compact facilities. The (sub)PW laser systems that drive LPAs are currently operating at 1-10 Hz repetition rates, while the next generation of multi-kHz technologies are being aggressively pursued at various R&D facilities worldwide. The robustness and stability of LPAs can largely be traced back to the laser performance. Fluctuations in laser pointing and other laser parameters directly translate to variations in electron beam parameters. Here we present results from recent techniques that mitigate laser fluctuations in a two-fold approach: (1) develop on-line and non-perturbative high-power laser diagnostics, both for the high-power laser as well as for a correlated background laser [1], and (2) implementation of active feedback systems to stabilize the high-power laser. Experimental results [2] show that through execution of these efforts at the BELLA Center LPA facilities, we have made significant improvements to the LPA electron beam and light source stability.