European research activities towards a future DEMO gyrotron - Jelonnek, J.; Aiello, G.; Alberti, S.; Avramidis, K.; Bertinetti, A.; Bruschi, A.; Chelis, J.; Franke, T.; Gantenbein, G.; Garavaglia, S.; Granucci, G.; Grossetti, G.; et al. (EPJ Web of Conferences, 2017)