中文摘要：

为了发展大功率太赫兹辐射源,本文对大半径同轴谐振腔回旋管进行了理论和数值模拟研究,理论计算结果表明在同轴谐振腔中其角向对称的TE0n模式的截止频率与n近似成正比关系,与内外导体之间的距离近似成反比关系.根据上述特点作者设计了一只大半径同轴腔0.3THz、TE04模回旋管,数值计算和粒子模拟结果表明：大半径同轴谐振腔太赫兹回旋管与空心波导谐振腔回旋管相比具有很多优点：腔体尺寸相对较大,工作电流可以大幅度提高;其对称的TE0n模式与非对称的TEmn模式的间隔较大,有利于克服模式竞争.

英文摘要：

In order to develop high power Terahertz sources,a large radius coaxial cavity gyrotron has been studied in this paper.The results of theoretical calculation show that in a coaxial cavity the cutoff frequency of TE0n mode is almost proportional to n and in inverse proportion to the distance between inner and outer conductor.According to these characteristics a large radius coaxial cavity 0.3THz TE04 mode gyrotron is designed.The results of numerical calculation and PIC simulation show the large radius coaxial gyrotrons have a lot of advantages compared with the waveguide gyrotrons：the size of coaxial cavity is comparatively larger and outpwt power can be increased.The interval between TE0n and TEmn mode is increased which has improved mode competition greatly.