Plasma-based electron acceleration is arguably one of the most promising alternatives to more conventional radio-frequency acceleration techniques. Several landmark results have already been obtained, including accelerating fields exceeding 100 GV/m , charge-coupling in a multi-stage accelerator , and the laser-driven acceleration of electrons up to 8 GeV in only
20 cm of plasma . Due to the intrinsic asymmetry in the plasma-based accelerating fields, the acceleration of positrons is far more complex, requiring seed positron beams with rather challenging characteristics, including sub-micron emittance and ultra-short longitudinal length
(1 to 10s of microns).
Our group has recently demonstrated that positron beams with such characteristics can be generated in a fully laser-driven configuration [4-6], opening up the possibility for the extensive experimental study of plasma-based acceleration of positrons, with the long-term goal of working towards a plasma-based collider . Numerical work carried out by our group  has
demonstrated that fs-scale positron beams containing ~pC of charge in a 5% energy slice at the GeV level can be generated using the upcoming next generation of laser facilities, currently either under construction or commissioning. For instance, a dedicated positron beam line based
on a plasma source of this kind has been designed for the EuPRAXIA facility , currently being reviewed by ESFRI.
In this seminar, preliminary experimental work at the sub-GeV level [10,11] will be presented, confirming the numerical predictions reported in  and demonstrating the possibility of measuring, simultaneously and in a non-invasive manner, all the main positron beam characteristics, including spectrum, overall charge, energy-resolved emittance, and
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