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Stable Sheet-Beam Transport in Periodic Nonsymmetric Quadrupole Field
Zhanliang Wang,Yubin Gong,Yanyu Wei,Zhaoyun Duan,Huarong Gong,Zhigang Lu,Lingna Yue,Hairong Yin,Jin Xu,Yuanbao Li,Pukun Liu,Gun-Sik Park IEEE 2010 IEEE transactions on plasma science Vol.38 No.1
<P>Stable sheet electron-beam transport is critical for sheet-beam microwave device which is attractive for high-power millimeter wave to terahertz-regime radiation. This paper studies the stable sheet-beam transport in periodic nonsymmetric quadrupole field. First, the conditions for stable round- and sheet-beam transport in periodic magnetic quadrupole field are deduced. In the deduction, we find that the symmetric quadrupole field and the space-charge field of sheet beam are not well matched. In order to settle this problem, we use periodic nonsymmetric quadrupole field instead of periodic symmetric quadrupole field to transport sheet beam. Finally, 3-D PIC simulations verify the conditions for stable sheet-beam transport and show that periodic nonsymmetric quadrupole field is intrinsically well suited for sheet-beam transport.</P>
A Rectangular Groove-Loaded Folded Waveguide for Millimeter-Wave Traveling-Wave Tubes
Mingliang Liao,Yanyu Wei,Yubin Gong,Jun He,Wenxiang Wang,Gun-Sik Park IEEE 2010 IEEE transactions on plasma science Vol.38 No.7
<P>A folded waveguide (FW) is a promising slow-wave structure (SWS) for millimeter-wave traveling-wave tubes (TWTs) with the advantages of high power and considerable bandwidth. A novel rectangular groove-loaded FW SWS is analyzed for the purpose of gaining higher power with a smaller size compared with the normal circuit. The high-frequency characteristics, including dispersion properties and interaction impedance, are investigated by numerical simulation, and the nonlinear large-signal performance of such a TWT is also analyzed by a 3-D particle-in-cell code MAGIC3D. Compared with a normal circuit, larger gain and electronic efficiency together with notably higher output power at a Ka-band are predicted by the simulation. Meanwhile, the novel circuit is also much shorter than the normal circuit with good performance at the working frequencies. It, therefore, will favor the miniaturized design of a high-power millimeter-wave TWT.</P>
Investigation on a W Band Ridge-Loaded Folded Waveguide TWT
Jun He,Yanyu Wei,Yubin Gong,Wenxiang Wang,Gun-Sik Park IEEE 2011 IEEE transactions on plasma science Vol.39 No.8
<P>A W-band ridge-loaded folded waveguide traveling-wave tube (FWTWT) is modeled, and the nonlinear interaction between the electron beam and the electromagnetic field is investigated by utilizing a 3-D particle-in-cell (PIC) code, MAGIC. The process of beam-wave interaction for millimeter wave TWT is presented, including the longitudinal momentum of the electron, the averaged radiation power, and the influence of input power on output power. Compared with the conventional FWTWT at 95 GHz, the ridge-loaded FWTWT obtains a 29.3% higher output power and shortens 31.7% interaction distance. The radiation power and the gain of TWT are raised up in most of the working band covering from 85 to 97 GHz, indicating effectual enhancement of beam-wave interaction by loading ridge. Furthermore, the novel FWTWT works in 7-GHz bandwidth with output power varying only 1 dB throughout the band.</P>