用于受控热核聚变的兆瓦级同轴腔回旋振荡器的注-波互作用分析

相对于高阶工作模式的单腔回旋管,同轴腔回旋管具有缓解模式竞争,提高单模工作的稳定性,以及增大功率容量的优点,宜用于受控热核聚变中的电子回旋共振加热和电子回旋电流驱动而受关注.详细地研究了工作频率为170 GHz,TE_(34,11),模同轴腔回旋管的结构参数、电子束参数及腔壁损耗对注-波互作用的影响.首先对170 GHz兆瓦级功率模式选择进行分析,给出了工作模式.再次,基于时域自洽非线性理论,编写了时域单模稳态注-波互作用程序,分析了电流、磁场强度和腔壁欧姆损耗对互作用的影响,并对工作参数进行了优化.模拟结果表明:当电子束电流为68 A,工作电压为65 kV,引导磁场强度为6.58 T时,可获得2.18 MW的输出功率,49.23%的效率,外腔壁上的欧姆损耗密度峰值为1.94 kW/cm~2,内导体表面的小于0.15 W/cm~2;互作用效率随速度零散增大而降低,输出频率向下偏移;电子注厚度对互作用也有相似的影响.

Beam-wave interaction analysis of a megawatt coaxial cavity gyrotron for controlled thermonuclear fusion

Relative to the single-cavity gyrotrons operating in high-order mode, the coaxial cavity gyrotrons have the advantages of reducing mode competition, improving the stability of single mode operation and increasing the power capacity. Therefore, the coaxial cavity gyrotrons are more suitable for electron cyclotron resonance heating and electron cyclotron current driving in controlled thermonuclear fusion and attract much attention. The effects of structure parameters, electron beam parameters and ohmic losses on the beam-wave interaction of a coaxial cavity gyrotron operating at 170 GHz, mode were investigated in detail. Firstly, the mode selection of 170-GHz MW-class gyrotrons was analyzed and mode was chosen as the operating mode. Secondly, based on the time-dependent self-consistent nonlinear theory, a time-domain single-mode steady-state code was written to study the beam-wave interaction. The influences of the beam current, the magnetic field and the ohmic losses on the cavity walls were analyzed and the operating parameters were optimized. The simulation results show that when the voltage, the beam current and the axial guiding magnetic field are designed to be 65 kV, 68 A and 6.58 T, an output with 2.18 MW power and 49.23 % efficiency can be obtained, the peak ohmic loss density on the outer wall of the cavity is 1.94 kW/cm², and the peak ohmic loss density on the insert is less than 0.15 W/cm². The interaction efficiency decreases with the increase of electron velocity spread, and the output frequency shifts downward. The thickness of electron beam has similar effects on the interaction.