Description
Electron-positron pairs are produced by ultra-intense (multi-petawatt) laser pulses through the multiphoton Breit-Wheeler process [1]. The required peak intensity can be reduced by forming a tightly confined hot spot using several counter-propagating pulses [2,3]. Our aim is to further optimise this approach and move it closer to experimentally achievable conditions.
We simulate these setups via PIC-code Smilei [4], where we need to use tightly focused beams tailored to our application. A particular challenge is to reliably implement boundary conditions for many incident beams from coming arbitrary directions. Once the beam is estimated analytically, it requires to project it onto the boundaries. Once the field is not known, it is necessary to find a reliable efficient way to propagate the field considering its vectorial nature [5] in tight geometry beyond the actual native Smilei routines [6,7].
This contribution will present these schemes and outline ongoing development.
References
[1] G. Breit and J. A. Wheeler, Collision of Two Light Quanta, https://doi.org/10.1103/PhysRev.46.1087
[2] M. Jirka and S. Bulanov, Effects of colliding laser pulses polarization on cascade development in extreme focusing, https://doi.org/10.1103/PhysRevLett.133.125001
[3] M. Jirka, J. Vabek, and S. V. Bulanov, QED cascade in multiple radially polarized laser pulse collision, https://doi.org/10.1088/1361-6587/ae60a3
[4] J. Derouillat et al., Smilei : A collaborative, open-source, multi-purpose particle-in-cell code for plasma simulation https://doi.org/10.1016/j.cpc.2017.09.024
[5] I. Thiele, S. Skupin, and R. Nuter, Boundary conditions for arbitrarily shaped and tightly focused laser pulses in electromagnetic codes, https://doi.org/10.1016/j.jcp.2016.06.004
[6] F. Pérez and M. Grech, Oblique-incidence, arbitrary-profile wave injection for electromagnetic simulations, https://doi.org/10.1103/PhysRevE.99.033307
[7] K. Matsushima et. al, Fast calculation method for optical diffraction on tilted planes by use of the angular spectrum of plane waves, https://doi.org/10.1364/JOSAA.20.001755
