Polarization dependent beam pointing jitter in laser wake field accelerators

Laser wakefield accelerators (LWFA) have rapidly evolved from proof-of-principle experiments to advanced concepts focusing on improving their beam properties, stability and reliability. With various techniques LWFAs have achieved high energy, low energy spread, high charge and low emittance beams with high spectral stability, essential for a high quality accelerator. The stability of beam pointing and source position however, is equally critical. Here we present experimental results, which show a laser polarization dependent contribution to electron beam pointing jitter in laser wakefield accelerators (LWFA). We develop a theoretical model for the polarization dependence in terms of the transverse dynamics of trapped electrons, resonantly driven by bubble centroid oscillations. The latter are generated by the carrier wave phase evolution at the self-steepened laser pulse front. In the model, the polarization dependent jitter originates from shot-to-shot fluctuations of the laser carrier envelope phase. This suggests that for non-CEP stabilized systems the polarization dependent jitter may form an ultimate limit to beam pointing stability in LWFAs.