Matching strategies for a plasma booster

Abstract

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.

Plasma boosted electron beams for driving Free Electron Lasers

“…Again, we scan initial electron beam size and injection phase for best performances. We also allow for a non zero value of the α T Twiss parameter, since it has been reported [19,28] that a converging beam envelope at the ramp beginning can improve quality preservation. We notice that the witness must be injected closer to the driver with respect to the ideal setting: this is due to the fact that in the ramps, due to low plasma density and larger driver spot size, the laser group velocity is larger than in the plateau.…”

“…Another non ideal feature whose effect cannot be predicted by scalings is the unavoidable presence of plasma ramps at the capillary tips, due to gas leakage. It has been shown how these features can be fruitfully exploited to ease matching into/from plasma [19]; however, this would require a lengthy optimization both of transport and of capillary engineering so, in this work, we will only assess the maximum acceptable ramp length for avoiding an excessive beam degradation, assuming the ramps have an exponential behavior.…”

High quality electron bunches for a multistage GeV accelerator with resonant multipulse ionization injection

“…5). Simulation of the laser-plasma (including ionization) process have been performed with the 2D-cylindrical hybrid QFluid code [50], including cross checks with ALaDyn code in the hybrid plasma configuration (fluid plasma background with kinetic trapped particles) and in the laserenvelope approximation [51][52][53].…”

Overview of plasma lens experiments and recent results at SPARC_LAB

“…A density shaping can be achieved by either varying the capillary diameter along its length [10], or tailoring the gas profile [11], or eventually exploiting optical-ionization methods [12]. Advantages of density ramps are discussed in [13,14,15], however ramps are still an open question and consequently under investigation due to their cumbersome nature. We notice that ramps can be formed by non-fully ionized gas eventually non-even in thermal equilibrium, conditions that might affect bunch quality at some degree.…”