Complex and catastrophic ion beam focusing with a very thin electrostatic square rainbow lensS. Grujović Zdolšek, N. Nešković, I. Telečki and M. ĆosićEur. Phys. J. Plus, 137 4 (2022) 477DOI: https://doi.org/10.1140/epjp/s13360-022-02686-8