Schlieren imaging: a powerful tool for atmospheric plasma diagnostic Enrico Traldi, Marco Boselli, Emanuele Simoncelli, Augusto Stancampiano, Matteo Gherardi, Vittorio Colombo and Gary S. Settles EPJ Techn Instrum, 5 1 (2018) 4 Published online: 10 May 2018 DOI: 10.1140/epjti/s40485-018-0045-1