Laser plasma accelerators have the ability to produce high-quality electron beams in compact, all-optical-driven configurations, with the electron beams uniquely suited for a wide variety of accelerator-based applications. However, fluctuations and drifts in the laser delivery to the mm-scale plasma target (the electron beam source) will translate into electron beam source variations that can limit their utility for demanding applications like light sources. Based on previous work in developing a nonperturbative diagnostic for the high-power laser delivery at focus [1], we present a full four-dimensional active-stabilization system for the laser (transverse laser focus position and laser pointing angle in both transverse planes) and experimentally demonstrate how, as a result of the laser stabilization, critical parameters in the electron beam source were stabilized. Through the use of an energy resolved imaging system for the electron beam, we directly monitor the jitter in the transverse electron beam source location. Furthermore, the dispersion in the orthogonal plane to the magnetic spectrometer was recorded for each shot which is tied to the source pointing angle of the electron beam and, in part, driven by the angle of the laser at the interaction point. Our laser stabilization system reduced variation in the electron beam source location from ∼12 to 3 μm and reduced the dispersion jitter of the electron beam by 20%.

Efficiently shaping femtosecond, transverse Gaussian laser beams to flat-top beams with flat wavefronts is critical for large-scale material processing and manufacturing. Existing beam shaping devices fall short either in final beam homogeneity or efficiency. We present an approach that uses refractive optics to perform the majority of the beam shaping and then uses a fine-tune device (spatial light modulator) to refine the intensity profile. For the beam that we selected, circularly asymmetric with intensity fluctuations, our method achieved a uniformity of 0.055 within 90% of the beam area at 92% efficiency. The optimization involved an iterative beam shaping process that converged to optimum within 10 iterations.