Development of a 140GHz 3rd cyclotron harmonic gyro-peniotron oscillator

大功率毫米波管是聚变等离子体研究中电子回旋共振加热和等离子体诊断的重要器件。在大型核聚变装置中，尤其需要研制波长较短的亚毫米波管。高次回旋快波管比其他回旋快波管具有更低的磁场要求和更高的工作频率，因此高次回旋快波管适合于上述高功率高频应用。在本项目中，我们对第三回旋加速器gyro-peniotron的开发进行了以下工作。我们设计了TE<@2021<@D2模式腔体和电子枪，分别用于在回旋加速器频率三次谐波和60KV加速电压和10A加速电流束流条件下工作的试管。该试管的设计指标如下：振荡频率为140GHz，启动电流为4A，输出功率为45.5KW，效率为9.0%。试管是在东芝公司制造的。实验结果与讨论139.5GHz的第三次回旋加速器谐振振荡在束流为5A时产生，输出功率随束流的增大而增大。通过测量输出波导的辐射方向图，验证了振荡模式为TE_<021>模式。目前，在光束电流为6A时，最大输出功率为3.3KW。我们期望通过重新调整试管中心轴和所用磁铁的排列，能够大大增加其输出功率。从仿真结果中没有观察到预期的模式竞争。

High power millimetre wave tubes are great important devices in fusion plasma researches for the electron cyclotron resonance heating and plasma diagonostics. The development of tube with shorter wavelength up to submillimetre wave range is especially required in large fusion devices. The high harmonic gyro-peniotron is desirable for such high power and high frequency applications as the above because of its lower magnetic field requirement and higher operation frequency due to the favorable peniotron operation mechanism than these of other cyclotron fastwave tubes.In this project, wa have performed the following tasks concerning with the 3rd cyclotron gyro-peniotron development.1. Design of 140GHz gyro-peniotron We designed the TE<@2021<@D2 mode cavity and the electron gun, thich were used for the test tube operating at the third harmonics of the cyclotron frequency and at the beam conditions of acceleration voltage and curent of 60KV and 10A, respectively. The design specifications of the test tube are as follows: Oscillation frequency is 140GHz, starting current is 4A and the output power and the efficiency are 45.5KW and 9.0%, respectively. The test tube was fabricated at Toshiba corporation.2. Experimental results and discussions The 3rd cyclotron harmonic oscillation at 139.5GHz initiates at the beam current of 5A and the output power increases with increase of the beam current. The mode of oscillation is verified to be TE_<021> mode by measuring the radiation pattern from the output waveguide. Up to date, the maximum output power of 3.3KW was obtained at beam current of 6A. We are expecting to be able to increase considerably its output power by readjusting the arrangement of centre axes of the test tube and the used magnets. No mode compitition has been observed as expected from the simulation results.