Final Report Summary - FEMTOELEC (Innovative Femtosecond laser-plasma based electron source for studying ultrafast structural dynamics)
Until recently, laser wakefield acceleration relied on large-scale laser systems that delivered typically one laser pulse per second. This low repetition rate made it difficult to use the electron beams for applications. In FEMTOELEC, we proposed a new approach to laser wakefield acceleration using a high-repetition rate and small energy laser system. We succeeded in producing electron beams with a laser containing 1000 times less energy and delivering 1000 pulses per second, i.e. three orders of magnitude more than before. To do this, we developed a unique laser system that delivers the shortest laser pulses ever obtained at the multi-milliJoule level. We managed to produce laser pulses with a single optical cycle of 3.5 fs, and to use them to accelerate electrons to relativistic energies. In addition, we showed experimentally that the electron beam can be used to “image” a crystal lattice via electron diffraction and to follow its dynamics on ultrafast time scales. These first proof-of-principle experiments confirm the huge potential of laser driven electron beams for ultrafast imaging. Beyond the proof-of-concept, more work is now required to turn this electron source into a user-friendly instrument, able to deliver day-to-day operation with sub-10 fs temporal resolution. In conclusion, we showed that laser wakefield acceleration could be scaled to box-size laser systems, operating at high repetition rate and opening the way to applications in ultrafast imaging.