Topological acceleration
The flexibility on the plasma topology is a distinctive aspect of plasma based accelerators that remains nearly unexplored. It is a distinctive property of the plasma, which contrasts with conventional accelerators. The plasma provides great flexibility on its topology because plasma wakefields are determined by electrons, whose trajectory can be precisely controlled using intense lasers. The freedom to modify the plasma wakefield topology is very important because the topology defines crucial aspects of the field structure in plasma accelerators. For example, the typical wakefield structure in the plasma is spherical. This geometry provides linear accelerating and focusing fields for electrons [lu'06]. However, considering instead doughnut-shaped plasma waves, positron acceleration can also occur [vieira'14].
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Recently, we have demonstrated that intense lasers can impart orbital angular momentum into plasma waves, and excite a new type of twisted plasma waves [vieira'18]. To achieve this, we considered a special class of lasers that have a helical intensity profile, which is reminiscent of a cork-screw. These lasers are then known as light springs [pariente'15].
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Controlling the wakefield topology is interesting as it provides a new fundamental degree of freedom to control the properties of the accelerated particles. We have illustrated this principle by showing that twisted plasma waves can accelerate electrons with quantized orbital angular momentum levels. As these electrons may then also carry an intrinsic magnetic moment, they could provide new tools to probe magnetic properties of matter. Moreover, as electrons accelerate in the plasma, they perform spiraling trajectories, thereby resembling a mini-synchrotron. Thus, such electron bunches, which are challenging to produce using conventional accelerators, may have interesting applications in radiation generation.
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The movie below, from a 3D Osiris simulation, shows the spiraling electron motion during acceleration in a twisted plasma wave. The twisted To know more please find the paper here: J. Vieira et al. Phys. Rev. Lett. 121, 054801 (2018).
Bibliography:
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[lu'06] W. Lu et al., Phys. Rev. Lett. 96, 165002 (2006)
[vieira'14] J. Vieira et al., Phys. Rev. Lett. 112, 215001 (2014)
[pariente'15] G. Pariente et al., Optics Lett. 40, 2037 (2015)
[vieira'18] J. Vieira et al, Phys. Rev. Lett. 1212, 054801 (2018).
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