Improved Magnetron Injection Guns for Gyrotrons

75258-Gyrotrons and gyroklystrons, used for high power radio frequency applications in the DOE Fusion program, are being adversely impacted by poorly performing cathodes for which the current emission is not uniform over the entire surface. This results in a reduced operating efficiency along with excessive power densities in the spent beam collector. This project will determine the causes of emission non-uniformity and develop cost-effective, uniformly emitting cathodes for improved performance. Both temperature and work function issues will be addressed, as well as improvements in electron gun design and cathode manufacture. In Phase I, an existing test facility will be modified to incorporate infrared temperature measurements, so that the relative impact of temperature and work function can be determined. This information, along with simulations using two- and three dimensional thermomechanical and beam optics tools, will be used to evaluate the impact of changes in cathode materials, mechanical and geometrical variations, and modifications to manufacturing processes and procedures. Commercial Applications and Other Benefits as described by the awardee: Increased gyrotron performance should impact several applications, including electron cyclotron heating, current drive, and the control of instabilities in fusion plasmas. Gyrotron cost reduction also would enable these devices to be used in other applications, including industrial heating and defense systems.