Some design data for the second harmonic, 1 MW, 15 GHz gyrotron for plasma heating at the NSTX tokamak

There is an interest in using long-pulsed gyrotrons for electron Bernstein wave heating and current drive at the NSTX tokamak at Princeton Plasma Physics Laboratory. Parameters of this tokamak dictate the choice of gyrotron radiation frequency about 14-15 GHz, and the goal is to develop a gyrotron delivering 1 MW power in 2-3 second pulses with an efficiency of about 50%. Preliminary design data for such a gyrotron operating at the fundamental cyclotron resonance were presented in (R. J. Temkin et al, MIT presentation at the gyrotron review meeting at CPI, Dec. 10, 2003). There can be an alternative solution, which is a gyrotron operating at the second cyclotron harmonic. The present paper contains some design data for such a second harmonic gyrotron.