Active control for high repetition-rate laser wakefield accelerators

Many potential applications of laser accelerator sources require operation at high repetition rate. Here, few-milliJoule pulses are generated at kilohertz repetition rate for wakefield acceleration. A genetic algorithm is implemented using a deformable mirror with the wakefield electron beam signal optimized onto several different masks used as feedback. This procedure allows a heuristic search for the optimal wavefront under laser-plasma conditions that is not known a priori. We are able to improve the electron beam charge and angular distribution by an order of magnitude. These improvements do not simply correspond to finding the ‘best’ focal spot, as the highest quality vacuum focal spot produces an inferior electron beam. The saved deformable mirror configurations coupled with the use of a Shack-Hartmann wavefront sensor promise to characterize the laser phase front that induces a plasma wave which provides optimal accelerating fields. In progress is the addition of a cold jacket that insulates the gas delivery system to achieve a gas target with higher density for complete characterization.