We report the first observation of large amplitude Langmuir waves in a plasma of nanometer-scale clusters. The shape of these wakefields is captured by a single-shot frequency-domain holography diagnostic at an oblique angle of incidence. The wavefronts are observed to curve backwards, in contrast to the forwards curvature of wakefields in uniform plasma. The first wakefield period is longer than those trailing it. The features of the data are well described by a fully relativistic two-dimensional particle-in-cell simulation.
|Working group||Laser-driven electron acceleration|