This paper presents a theoretical study of a matching strategy for the laser-plasma wakefield accelerator where the injected electron beam is produced by an external source. The matching is achieved after an initial focusing using conventional beam optics, combining a linear tapering of plasma density and the increasing non linearity of the plasma wake due to the focusing of the laser driver. Both effects contribute in increasing the focusing strength from an initial relatively low value, to the considerably higher value present in the flat top plasma profile, where acceleration takes place. The same procedure is exploited to match the beam from plasma to vacuum once acceleration has occurred. Beam loading plays a crucial role both at the very beginning and end of the whole process. In the last stage, two more effects take place: a partial emittance compensation, reducing emittance value by a sizable amount, and a reduction of the energy spread, due to the relevant beam loading operating when the laser is defocused.
Laser and plasma accelerators