Above the illustration in the text, the paper references work from 2001-2006 for motivating that geometry:

    [19]  J. Khachan and S. Collis, Phys. Plasmas8, 1299 (2001).
    [20]  J. Khachan, D. Moore, and S. Bosi, Phys. Plasmas10, 596 (2003).
    [21]  O.  Shrier,  J.  Khachan,  S.  Bosi,  M.  Fitzgerald,  and  N.Evans, Phys. Plasmas13, 012703 (2006)

In particular all three citations refer to Joseph Khachan's work:

https://sydney.edu.au/science/about/our-people/academic-staf...

And Bosi seems to have been at Sydney at the time as well:

https://www.une.edu.au/staff-profiles/science-and-technology...