late Dr. Robert J. (Bob) Barker, a strong and influential propo- nent of HPM research, as well as a prolific contributor to the. IEEE and the Nuclear and Plasma ...
IEEE TRANSACTIONS ON PLASMA SCIENCE, VOL. 42, NO. 6, JUNE 2014
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Guest Editorial The Fifteenth Special Issue on High-Power Microwave Generation
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HE publication this year of the Fifteenth Special Issue on High-Power Microwave Generation continues a tradition in the field dating back to 1985. While the editors are concerned with the somewhat sparse selection of papers in this issue, the diversity of authorship both geographically and across research institutions is gratifying. The body of work represented by this volume emphasizes a clear continuation, in fact acceleration, of the use computational tools, which has represented a consistent trend in recent issues. Most notable are Particle in Cell (PIC) codes, which have enabled the optimization and virtual prototyping of a variety of High Power Microwave (HPM) sources. The overwhelming success of modern computational tools has all but eliminated the need for empirical iteration in the hardware realization of a given source design. Instead, any iteration proceeds during a virtual, numerical design process, and the final design is the only one built, saving both time and money. The current volume begins appropriately with a tribute to the late Dr. Robert J. (Bob) Barker, a strong and influential proponent of HPM research, as well as a prolific contributor to the IEEE and the Nuclear and Plasma Sciences Society. Dr. Barker was an accomplished computational plasma physicist is his own right, enabling the development of the two dimensional MAGIC code and three dimensional SOS PIC code. Undoubtedly, however, most who knew him would agree that his greatest contribution to the field came as a Program Manager with the Air Force Office of Scientific Research (AFOSR). His tenure there led to AFOSR becoming the principal funding agent for basic research across the breadth of the HPM arena. He strongly emphasized the development and use of PIC codes within the HPM research community. The fruits of this emphasis are abundantly clear in the papers comprising this issue. Next is a paper by Scott A. Rice and John Verboncoeur comparing the results of two secondary electron emission models, one proposed by Vaughn and one by Furman and Pivi. Both of these models are in use in numerical simulation codes. Then, a paper by Yuan Liang describes the analysis of dispersion and gain in nonstaggered bilateral metal grating periodic structures. This paper includes numerical analysis of the effects of various parameters on the linear growth rate in these structures. M. R. Amin, K. Ogura, J. Kojima, and M. R. H. Sagor analyze trapezoidally corrugated slow wave structures for backward wave oscillators, including numerical solution of the dispersion relation of the structures. Next, Yabin Zhang, Yubin Gong, Zhanliang Wang, Shuaihong Liu,
Yanyu Wei, Zhaoun Duan, Xianbao Shi, Yanshuai Wang, Luqi Zhang, and Qing Zhou numerically and experimentally study a high power Ka-band rectangular double grating sheet beam BWO with a graphite cathode. Ayush Saxena, Kunal Shambharkar, Navdeep Singh, and Faruk Kazi report on the 3-D PIC code simulation of a reflex triode virtual cathode oscillator. The simulations compare favorably with experimental results. Then, Sebastien Pottier, Friedman Tchoffo Talom, Dominique Jousse, Franck Hamm, Patrick Sirot, and Rene Vezinet discuss a pulsed high-power compact antenna for high-power microwave applications. The antenna works over a large bandwidth and can be excited by a variety of HPM sources. The Special Issue concludes with a manuscript, in keeping with the theme of advanced computational tools, from Kartikeyan Machavaram, Parth Kalaria, and Manfred Thumm discussing the design of a high efficiency tapered cavity gyrotron for fusion-plasma heating applications. This volume illustrates the continued and expanding use of computational tools in HPM research, enabling the full realization of the promise of virtual prototyping. Not only do computational tools enable a faster, less expensive design process, and more complete exploration of the design space, but the designs are more robust than ever before. Many devices that were previously impossible can now be designed with the aid of computational tools. The editors would like to express their appreciation to the contributors to this Special Issue, and particularly to the individuals who invested considerable time and effort in reviewing the manuscripts. The Guest Editors would like to thank Dr. Monica Blank for her support and advice and, of course, the IEEE Editorial Staff without whom this Special Issue would not be possible. A NDREW D. G REENWOOD Air Force Research Laboratory Kirtland AFB, NM 87117 USA F. M ARK L EHR, Chief Engineer High Power Electromagnetics Division Air Force Research Laboratory Directed Energy Directorate Kirtland AFB, NM 87117 USA E MILIO A. NANNI Massachusetts Institute of Technology Cambridge, MA 02139 USA
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