<?xml version="1.0" encoding="UTF-8"?><xml><records><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Xiang-Bo Qi</style></author><author><style face="normal" font="default" size="100%">Chao-Hai Du</style></author><author><style face="normal" font="default" size="100%">Juan-Feng Zhu</style></author><author><style face="normal" font="default" size="100%">Shi Pan</style></author><author><style face="normal" font="default" size="100%">Pu-Kun Liu</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">The design of a multi-harmonic step-tunable gyrotron</style></title><secondary-title><style face="normal" font="default" size="100%">Physics of Plasmas </style></secondary-title></titles><dates><year><style  face="normal" font="default" size="100%">2017</style></year></dates><urls><web-urls><url><style face="normal" font="default" size="100%">http://aip.scitation.org/doi/abs/10.1063/1.4977452</style></url></web-urls></urls><volume><style face="normal" font="default" size="100%">24</style></volume><pages><style face="normal" font="default" size="100%">033101</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">&lt;p&gt;&lt;span&gt;The&amp;nbsp;&lt;/span&gt;theoretical&lt;span&gt;&amp;nbsp;study of a step-tunable&amp;nbsp;&lt;/span&gt;gyrotron&lt;span&gt;&amp;nbsp;&lt;/span&gt;controlled&lt;span&gt;&amp;nbsp;by successive excitation of multi-harmonic modes is presented in this paper. An axis-encircling&amp;nbsp;&lt;/span&gt;electron beam&lt;span&gt;&amp;nbsp;is employed to eliminate the harmonic mode competition. Physics images are depicted to elaborate the multi-harmonic interaction mechanism in determining the operating parameters at which arbitrary harmonic tuning can be realized by&amp;nbsp;&lt;/span&gt;magnetic field&lt;span&gt;&amp;nbsp;sweeping to achieve&amp;nbsp;&lt;/span&gt;controlled&lt;span&gt;&amp;nbsp;multiband frequencies' radiation. An important principle is revealed that a weak coupling coefficient under a high-harmonic interaction can be compensated by a high&amp;nbsp;&lt;/span&gt;&lt;em&gt;Q&lt;/em&gt;&lt;span&gt;-factor. To some extent, the complementation between the high Q-factor and weak coupling coefficient makes the high-harmonic mode potential to achieve high efficiency. Based on a previous optimized&amp;nbsp;&lt;/span&gt;magnetic cusp&lt;span&gt;&amp;nbsp;gun, the multi-harmonic step-tunable&amp;nbsp;&lt;/span&gt;gyrotron&lt;span&gt;&amp;nbsp;is feasible by using harmonic tuning of first-to-fourth harmonic modes. Multimode simulation shows that the multi-harmonic&amp;nbsp;&lt;/span&gt;gyrotron&lt;span&gt;&amp;nbsp;can operate on the 34 GHz first-harmonic TE&lt;/span&gt;&lt;span&gt;11&lt;/span&gt;&lt;span&gt;&amp;nbsp;mode, 54 GHz second-harmonic TE&lt;/span&gt;&lt;span&gt;21&lt;/span&gt;&lt;span&gt;&amp;nbsp;mode, 74 GHz third-harmonic TE&lt;/span&gt;&lt;span&gt;31&lt;/span&gt;&lt;span&gt;&amp;nbsp;mode, and 94 GHz fourth-harmonic TE&lt;/span&gt;&lt;span&gt;41&lt;/span&gt;&lt;span&gt;&amp;nbsp;mode, corresponding to peak efficiencies of 28.6%, 35.7%, 17.1%, and 11.4%, respectively. The multi-harmonic step-tunable&amp;nbsp;&lt;/span&gt;gyrotron&lt;span&gt;&amp;nbsp;provides new possibilities in millimeter–terahertz source development especially for advanced terahertz applications.&lt;/span&gt;&lt;/p&gt;</style></abstract><issue><style face="normal" font="default" size="100%">3</style></issue></record></records></xml>