Laboratoire d'Optique Appliquée


Jun 22 2022


10 h 30 min

Generation and control of high-quality electron beams using Laser plasma WakeField Accelorators (LWFAs)

Shock-injection in laser driven plasma-based accelerators (LWFAs) are proofed to be an elegant and efficient approach for generating high quality electron beams. Yet, the charge of the produced beams is still limited to tens of pc, reducing then its use for a wider range of applications. The possibility to generate high charge beams by keeping a good quality, stays to be explored. Moreover, despite former studies focused on separate physical processes such as for example beam loadings, repulsive defocusing force, and laser evolution, a more general investigation of the plasma density parameters on the final beam parameters is required.

In this research, PIC simulations are performed to investigate the possibilities to improve plasma density parameters with shock (the density ratio , the downramp length  and the downramp position ) for producing high quality and high charge electron beams in the hundreds of MeVs range of energy.

We understand that the longitudinal distribution of the beam current  plays an important role in the injected beam charge as well as energy performance. Ways to tailoring  is studied.

Figure 1 Two examples of beam energy spectrum (subfigure a. and subfigure b.) corresponding to two downramp lengths . For both cases,  and , only downramp length changes,   and   respectively. The beam energy evolution through propagation distance z can be seen from the beam energy spectrum. The brighter the region, the lower the energy spread through the region. The beam longitudinal phase spaces for different propagation length are shown in the inset figures for better illustrating the beam energy evolution. Red lines in the longitudinal phase space inset figures are the beam current distribution through the longitudinal coordinate.


Figure 1 shows the beam energy spectrums for two beam current distributions. The beam energy evolution is plotted as red solid line and the beam energy spread  is plotted as colored lines. For both simulations, the charges of the injected beams are nearly equal with Q = 186 pCs, with different current distribution (red lines in the inset figures). Our zone of interests for beam deliveries are where the minimum energy spread min is found. For case(a)  with corresponding beam energy  and for case (b) with . The obtained beam parameters are adapted to applications of electron cancer therapies.

In this talk, ways to obtain desirable  are also discussed in details for potential applications like FELs and driver beams for PWFAs.