Overview of Recent Gyrotron RD at KIT in View of the EU DEMO - Avramidis, K. A.; Aiello, G.; Brucker, P.T.; Gantenbein, G.; George, M.; Grossetti, G.; Illy, S.; Joannidis, I.C.; Jin, J.; Kalaria, P.C.; Marek, A.; Pazonakis, I.G.; et al. (International Conference on Infrared, Millimeter, and Terahertz Waves, IRMMW-THz, 2018)