Laser Plasma Electron Acceleration with kHz Lasers

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Laser-plasma acceleration has emerged as a promising technique for producing electron beams in a compact manner. In the majority of cases, 100 TeraWatt to PetaWatt scale laser systems, with rather low repetition rates (Hz or less), are used to drive such accelerators and to produce electron beams up to the GeV scale. However, many applications require higher repetition rates up to the kHz level and beyond. Very recently, first proof-of-principle experiments have demonstrated laser-plasma acceleration of few-MeV electrons at kHz repetition rates. These first results are encouraging but the observed beams are not useful for applications yet as they lack reliability and stability. The current project, HighRep, aims to bring kHz laser-plasma acceleration to a higher level of maturity. To do so, we will develop innovative targets to better control the injection into the accelerating plasma waves, which should, in turn, increase the stability, reliability and robustness of the electron source. The target developments will follow two main research paths: (i) micro-nozzles for producing controlled tailored gas-jet distributions at the micrometer level, permitting for instance to trigger electron injection in density transitions, (ii) cluster targets with micrometer positioning of single clusters, for controlling injection and increasing the electron energy to 10 MeV and beyond. Laser-plasma accelerators have the potential of producing femtosecond X-ray bursts via betatron radiation of the electrons in the plasma wakefield. Within HighRep, we will carry out first measurements of the emitted X-UV light at kHz repetition rate. The project is crucially based on the complementarity of the French and German groups, both in terms of expertise and equipment. In particular, the collaboration between the two groups will permit to perform experiments on two different 1 TW state-of-the-art laser systems that have very different parameters. This will allow us to study kHz laser-plasma acceleration in different regimes and to estimate which laser technology is most promising.