Development of reflection gratings for advanced ECRH scenarios Burkhard Plaum, Martin Schubert, Achim Zeitler, Walter Kasparek, Carsten Lechte, Jörg Stober and ASDEX Upgrade Team EPJ Web Conf., 203 (2019) 04012 Published online: 25 March 2019 DOI: 10.1051/epjconf/201920304012