The numerical and experimental investigation of gyro-multiplier configurations
The numerical and experimental investigation of gyro-multiplier configurations
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发表时间：
2013-05
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通讯作者：
D. Constable
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作者：
D. Constable
本论文探讨了两种不同结构的回旋倍增器的可行性，这两种结构都工作在电子回旋频率的四次谐波。完整的数值建模和设计的一种新的，单腔陀螺倍增器实验的测试组件已被记录。此外，还进行了具有三个不同空腔部分的配置的数值模拟。将八倍方位角的谐振引入到圆柱形腔的壁中允许实现单腔陀螺倍增器布置，其中分别在37.5GHz和75 GHz的频率下产生第二谐波TE 2，2和第四谐波TE 4，3谐振。相互作用区域的平均半径为8 mm，平均深度为0.7 mm，长度为39 mm。所用的理想电子束的电压为60 kV，电流在5 A和10 A之间，限制在约0.7 T的磁场中。两个发射频率的分离是通过使用一个6 mm长的截止锥来实现的;然而，模式转换到两个以上的截止模式已经在数值上得到了证明。第4次谐波中包含的功率估计约为10-50 W。输出锥形的扩展已被证明足以将模式转换信号减少一个数量级，同时不影响第四谐波信号的传播。还进行了刀口电子枪和冲击器系统的设计和模拟，预测最终的电子束具有~ 19%的速度扩散。为了证明相互作用区域对二次谐波信号的“冷”响应，还记录了几个附加部件的设计、构造和测试。新型开槽壁模转换器，能够产生TEm，1模式从矩形TE 1，0输入信号，已被证明是高光谱纯度和大，约10%的带宽。一组半径为3.98 mm、在37- 4,1 GHz之间工作的TE 2，1发射器已显示出约56%的转换效率，而一组半径为3.78 mm的TE 4，1模式的类似发射器在70-80 GHz之间显示出20%的转换效率。一组涟漪壁模式转换器，最大半径，8.7毫米，具有20个周期，轴向正弦涟漪，深度为0.30毫米，设计转换的TE 2，1模式到TE 2，2，也已被证明。这些转换器显示约20 MHz带宽，约38 GHz。使用这些耦合器证明了波纹相互作用区域色散对入射四极模的偏振不敏感，与理论一致。通过检查具有三个不同腔部分的陀螺倍增器设置，已经证明，通过在基波下操作第一腔和第三腔，可以从半径略大于初始腔的半径的第二腔实现有效地产生第四谐波信号。检查的相互作用区域的半径分别为0.7 mm、0.783 mm和1.5 mm，长度分别为2.4 mm、2.4 mm和3.6 mm。采用电压为80 kV、束流为0.7 A、螺距因子为1.4的理想化电子束，在~14.15 T的约束磁场下，可产生基频为342.5 GHz的TE 1，2和TE 1，3模，以及频率为1.37 THz的TE 4，6模四次谐波。虽然对所施加的场的大小敏感，但是估计包含在第四谐波信号中的最大功率为120 W。
This thesis examines the feasibility of two different configurations of gyromultiplier, both of which operate at the fourth harmonic of the electron cyclotron frequency. The full numerical modelling and design of components for the testing of a novel, single cavity gyro-multiplier experiment has been documented. In addition, numerical simulations of a configuration featuring three distinct cavity sections have also been conducted. The introduction of an eight-fold azimuthal corrugation into the walls of a cylindrical cavity allows for the realisation of a single cavity gyro-multiplier arrangement, with generation of 2nd harmonic, TE2,2, and 4th harmonic, TE4,3, resonances, at frequencies of 37.5 GHz and 75 GHz, respectively. The interaction region is of mean radius, 8 mm, with a corrugation depth, 0.7 mm, and is 39 mm in length. The idealised electron beam utilised is of voltage, 60 kV, with current between 5 A and 10 A, confined in a magnetic field of ~0.7 T. Separation of the two emission frequencies was intended through the use of a 6 mm length cut-off taper; however, mode conversion to two above cut-off modes has been numerically demonstrated. The power contained in the 4th harmonic has been estimated at ~10-50 W. Extension of the output taper has proven to be sufficient to reduce the mode converted signals by an order of magnitude, while not impinging on the propagation of the 4th harmonic signal. The design and simulation of a knife-edge electron gun and kicker system has also been performed, with the final beam predicted to have a velocity spread of ~19%. In order to demonstrate the “cold” response of the interaction region to the 2nd harmonic signal, the design, construction and testing of several additional components are also documented. Novel slotted wall mode converters, capable of generating TEm,1 modes from a rectangular TE1,0 input signal, have demonstrated high spectral purity and large, ~10% bandwidth. A set of TE2,1 launchers, of 3.98 mm radius, operating between 37-41 GHz have demonstrated ~56% conversion efficiency, while a similar set for the TE4,1 mode, of 3.78 mm radius, demonstrated 20% conversion efficiency, between 70-80 GHz. A set of ripple wall mode converters, of maximum radius, 8.7 mm, featuring a 20 period, axial sinusoidal ripple, of depth 0.30 mm, designed to convert the TE2,1 mode to a TE2,2, have also been demonstrated. These converters display ~20 MHz bandwidth, at ~38 GHz. Using these couplers demonstrated the corrugated interaction region dispersion was insensitive to the polarisation of incident quadrupole modes, in keeping with theory. By examining a gyro-multiplier setup with three distinct cavity sections, it has been demonstrated that by operating the first and third cavities at the fundamental harmonic, effective generation of a 4th harmonic signal can be realised from a second cavity of radius slightly larger than that of the initial cavity. The interaction regions examined were of radius 0.7 mm, 0.783 mm, and 1.5 mm, and of lengths 2.4 mm, 2.4mm and 3.6 mm, respectively. By using an idealised electron beam of voltage, 80 kV, beam current of 0.7 A, and pitch factor of 1.4, generation of the TE1,2 and TE1,3 modes at a fundamental frequency of 342.5 GHz, and 4th harmonic, polarised in the TE4,6 mode at a frequency of 1.37 THz has been predicted, for a modest confining magnetic field of ~14.15 T. Although sensitive to the magnitude of the applied field, the maximum power contained in the 4th harmonic signal has been estimated to be 120 W.