Series of powerful CW gyrotrons in the range 105 – 140 GHz Gregory Denisov, Igor Kazansky, Vladimir Malygin, Elena Soluyanova, Evgeny Tai and Aleksey Chirkov EPJ Web Conf., 147 (2017) 04003 Published online: 24 July 2017 DOI: 10.1051/epjconf/201714704003