Advanced Techniques and Record Results

Interaction of high-intensity laser pulse with supersonic gas-jets delivered by fast electromagnetic valves is the most common technique in LWF experiments worldwide. This kind of target allows a uniform, underdense plasma to be the interaction medium, with a density that can be tuned by managing 

A minor but promising line of investigation concerns the use of plasmas preformed from thin foil targets, via the exploding-foil technique. In this scheme, a thin foil of material, usually plastic of few micron thickness, is exploded in the interaction with the ASE pedestal. The main pulse interacts then with the preproduced plasma enabling the onset of the LWF mechanism. The choice of the thickness and material of the target, as well as 

Other experiments reported the production of high-energy electrons with a similar set-up, and showed the suitability of such relativistic bunches for nuclear activation techniques. It has been showed that nuclear reactions could be efficiently triggered by electrons from thin CH foil targets [69], and also that nuclear reactions can be a useful tool to characterize the electron beam accelerated with similar targets [70]. This point will be further developed in Sect. 8.4. 

Recently, an interesting correlation between the laser pulse polarization and the ellipticity of the electron beam profile has been observed [71]. However, no major influence of laser polarization on the efficiency of the electron acceleration processes has been observed so far, nor this influence has been predicted by theory and simulations, differently from the proton acceleration. For proton acceleration, a great improvement on bunch charge and quality are expected by using circularly polarized laser pulses focused on thin foils at ultra-high intensities [72-74]. 

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