大功率太赫兹返波管的数值模拟研究

Numerical Simulation Research on High Power Terahertz Backward Wave Oscillator

为了提升传统超高频小功率返波管的工作频率和输出功率,提出了一种过模表面波太赫兹返波管的紧凑结构.其中,慢波系统是在一段过模圆柱波导内壁沿圆周方向平行挖去若干个均匀环形槽构成的,相邻槽间距固定不变.该结构较之传统的单模结构能有效地降低管内电场强度、避免场击穿,提高系统在太赫兹频段的功率容量.采用数值模拟的方法对该慢波系统的结构参数进行了筛选,最终选取波导内半径为2 mm、槽深为0.2 mm、槽宽为0.6 mm、单周期长度为1 mm,共采用17个周期.利用2.5维粒子模拟程序对系统进行了热测实验,在电子注电压为550 kV、电子注电流为350 A的条件下,模拟得到了14.4 MW的峰值功率输出,其能量转换效率达到7.5%,振荡频率高于0.14 THz,时域波形及频谱特性良好.

In order to increase the work frequency and output power capacity of the conventional microwave backward wave oscillator （BWO）, a compact high power THz BWO was proposed. This THz BWO consisting of a large cross-section slow wave system operated as an overmoded surface wave oscillator. The slow wave system （SWS） was constructed as follows： a series of annular slots were formed in parallel in the Phi direction along the inner wall of an overmoded cylindrical wave guide, and the distance between every two slots was equivalent. This kind of SWS decreased the field strength in the structure efficiently and enhanced the power capacity of the device obversely in the THz regime. The structural parameters were optimized with the numerical simulation method, and a set of best parameters were presented. The hot test simulation of the device was implemented with the 2.5-dimensional particle-in-cell simulation programme. Under the condition of 550 kV voltage and 350 A current, the output power of 14.4 MW was achieved at the frequency of 0. 146 THz. And an efficiency of 7. 5% was also obtained with a perfect time plot and fine spectrum characteristic.