Preface
In December 2016, we published a focus issue on applications-oriented gyrotrons. In this sequel to the focus issue, we are pleased to highlight a very special paper entitled “Reflections on the University of Maryland’s program investigating gyro-amplifiers as potential sources for linear colliders.” It is a unique documentation of a series of milestones on ultra-high-power gyro-amplifiers based on more than 60 journal papers (including 6 PRLs) over a 2-decade span. In these efforts, the authors took an original approach for every key component of the device. Best known among them are a carefully researched relativistic magnetron injection gun with a thermionic cathode, advanced over-moded cavities, and high-power transmission line components. If this state-of-the-art technology is ahead of its time, it may only be slightly considering the rapid advance of particle accelerators.
Kwo Ray Chu
Guest Editor
March.31, 2017
TST, Vol. 10, No. 1, PP. 1-43
(Invited Review Paper) Reflections on the university of maryland’s program investigating gyro-amplifiers as potential sources for linear colliders
W. Lawson 1*, J. P. Calame 2, G. S. Nusinovich 3, and B. Hogan 4
1 Department of Electrical and Computer Engineering, University of Maryland, College Park, MD 20742, USA
2 present address: Naval Research Laboratory, 4555 Overlook Ave SW, Washington, DC 20375, USA
3 Institute for Research in Electronics and Applied Physics, University of Maryland, College Park, MD 20742, USA
4 present address: NOAA's National Ocean Service, 1305 East West Hwy, Silver Spring, MD 20910, USA
* Email: lawson@ece.umd.edu
(Received January10, 2017)
Abstract: Over two decades of research on gyro-amplifiers as potential sources for linear colliders at the University of Maryland is reviewed. A 500kV, 400-800A, 1ms pulse generator energized single- and double-anode Magnetron Injection Guns to generate high-energy, small-orbit, rotating beams in a peak magnetic field over ½ T. Over 20 different gyro-amplifier configurations were tested during the course of the project. The project produced over 60 journal articles and over 100 conference presentations. Key results included 30MW of peak power in a second-harmonic gyroklystron operating near 19.76GHz and about 80MW of peak power with a fundamental-mode coaxial gyroklystron near 8.6GHz. Along the way, advances were made in the theoretical modeling of small-signal and large-signal gyroklystron performance, scattering matrix formulations of various cavity configurations, Telegraphist equation formulations of mode transducers, Magnetron Injection Gun (MIG) design, overmoded directional coupler designs, and drift tube loading. Some efforts were also undertaken to better understand the physics of beam-wave interaction in relativistic gyro-amplifiers with the goal to increase the devices’ efficiency. Mostly due to problems with the final MIG, the program never achieved its goal of powering a small section for an advanced accelerator. Nonetheless, the program pushed the state-of-the-art in peak power density for microsecond accelerators, and tools developed and experience gained have positively impacted a number of gyro-amplifier devices at other institutions as well as gyro-amplifiers developed for other applications.
Keywords: Gyroklystrons, Gyro-amplifiers, MIGs, Microwave absorbers, Electromagnetic waves
doi: 10.11906/TST.001-043.2017.03.01
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