Experimental investigation of a compact relativistic magnetron with axial TE₁₁ mode radiation

As one of the relativistic electron tubes having compact configuration and high efficient output,the relativistic magnetron with direct axial radiation is very attractive in pulsed power and high power microwave fields for industrial and military applications.In this paper,the experimental investigation of a relativistic magnetron with axial TE 11 mode radiation is reported.Under a total length of ～ 0.3 m,volume of ～ 0.014 m 3,working at an applied voltage of 508 kV and a magnetic field of ～ 0.31 T,the relativistic magnetron radiates a microwave of 540 MW with the TE 11 mode at 2.35 GHz in the axial direction.The power conversion efficiency is 15.0%.After a lot of shots,the detected amplitudes of microwaves are nearly the same.The fluctuations of wave amplitudes are less than 0.3 dB.     

同轴辐射相对论磁控管的功率合成研究

同轴辐射相对论磁控管,又称具有衍射输出的相对论磁控管,是目前相对论磁控管在小型化和紧凑化方向发展的重要分支,也是有望成为最紧凑的窄带高功率微波源器件之一.根据同轴辐射相对论磁控管直接轴向辐射准TE11模式的方式和特点,开展了两路同轴辐射相对论磁控管共用一个喇叭的功率合成研究.通过对平行排列结果的分析讨论,提出了一种改善辐射方向性的方法和结构.最终的研究结果表明:当两路同轴辐射相对论磁控管并排靠近放置且夹角为7°,共用喇叭的参数为h=600mm,r=340mm时,π模反射系数为0.31,最大增益21.5dB,辐射模式为TE11模.     

双微波源共轴辐射馈线结构的设计

设计了一种将两个不同波段微波源输出微波馈向同一个馈源喇叭的双波段馈线结构。该结构不仅对两个微波源输出的TM01模进行了有效的模式转换,而且实现了两个波段的微波共用辐射天线。采用双弯曲圆波导模式转换器实现高频段微波源输出微波的模式转换和轴线的定量平移;采用中间模式为矩形波导TE10模的圆波导TM01模-同轴波导TE11模的模式转换器,实现低频段微波源输出微波的模式转换及与高频段微波源输出微波的共轴输出。数值仿真结果验证了设计思路的正确性。     

X波段过模弯曲圆波导TM01-HE11模式变换器研究

在波束波导和反射面天线的馈源应用中, 为了产生低副瓣且方向图等化的高斯波束, 需要将高功率微波转换为准高斯模HE₁₁模辐射. 本文利用弯曲圆波导可同时从TM₀₁模产生TE₁₁模和TM₁₁模的原理, 提出了采用双弯曲过模圆波导结构直接将TM₀₁转换为HE₁₁的模式变换器, 避免了常规微波领域中首先将TM₀₁转换为TE₁₁再用波纹式或半径渐变式TE₁₁-HE₁₁转换器转换为准高斯波束功率容量不足或尺寸过长的不足. 基于模式耦合理论和Taguchi优化算法对模式变换器的弯曲半径、相移直端长度及引入位置进行了优化, 使输出的TE₁₁和TM₁₁成一定比率, 以组成HE₁₁模式, 并对设计的模式变换器进行了全电磁波仿真分析, 结果表明输出波束的标量高斯含量在9.05–9.8 GHz范围内均高于99%, 理论功率容量可达4.5 GW. 关键词： 高功率微波 模式耦合理论 Taguchi优化算法 模式变换器     

HEM11 mode magnetically insulated transmission[2mm] line oscillator: simulation and experiment

A novel magnetically insulated transmission line oscillator (MILO) in which a modified HEM₁₁ mode is taken as its main interaction mode (HEM₁₁ mode MILO) is simulated and experimented in this paper. The excitation of the oscillation mode is made possible by carefully adjusting the arrangement of each resonant cavity in a two-dimensional slow wave structure. The special feature of such a device is that in the slow-wave-structure region, the interaction mode is HEM₁₁ mode which is a TM-like one that could interact with electron beams effectively; and in the coaxial output region, the microwave mode is TE₁₁ mode which has a favourable field density pattern to be directly radiated. Employing an electron beam of about 441 kV and 39.7 kA, HEM₁₁ mode MILO generates a high power microwave output of about 1.47 GW at 1.45 GHz in particle-in-cell simulation. The power conversion efficiency is about 8.4 % and the generated microwave is in a TE₁₁-like circular polarization mode. In a preliminary experiment investigation, high power microwave is detected from the device with a frequency of 1.46 GHz, an output energy of 43 J-47 J, and a pulse duration of 44 ns-49 ns when the input voltage is 430 kV-450 kV, and the diode current is 37 kA-39 kA.     

L波段全腔提取轴向输出相对论磁控管设计

设计了一种全腔提取轴向输出相对论磁控管。在模工作的N腔磁控管中, 该结构利用磁耦合的方式通过两个相邻谐振腔在一个扇形波导内激励起TE11模, 然后再由N/2个相位相同的扇形波导TE11模沿轴向向外传输。对L波段全腔提取轴向输出磁控管进行了仿真设计, 在600 kV, 6.3 kA的条件下, 获得1.89 GW微波输出, 功率转换效率50%, 微波频率1.57 GHz。该结构在径向方向上仅增加一个扇形波导厚度, 便于实现相对论磁控管的紧凑、高效设计。     

Magnetically insulated transmission line oscillator oscillated in a modified HEM11 mode

This paper puts forward a novel magnetically insulated transmission line oscillator (MILO) for the first time which takes a modified HEM11 mode as its main interaction mode. The excitation of the oscillation mode is made possible by carefully adjusting the arrangements of each resonant cavity in a two-dimensional (2-D) slow wave structure. The high frequency characteristics are analyzed and a PIC simulation is carried out; the detailed results are discussed to get a better understanding of this new MILO. Employing an electron beam of about 441 kV and 39.7 kA, it finds that the modified HEM11 mode MILO generates a high power microwave output of about 1.47 GW at 1.45 GHz. The power conversion efficiency is about 8.4% and the generated microwave is in a TE11-like circularly polarized mode; its polarization direction is decided by the rotation direction of the SWS.     

HEM11模磁绝缘线振荡器的高频分析

作为小型化和紧凑型的高功率微波源,磁绝缘线振荡器(MILO)在过去十几年里得到了广泛的研究和发展.在大多数研究中,最低的对称模一直被当作器件的主模.然而,由于结构的对称性或者电子发射均匀度不理想等原因,很容易激励起非对称模式.计算了MILO同轴结构中同时包含对称模和非对称模的本征方程.在此基础上,通过对结构的优化设计,提出了一种HEM₁₁模工作的MILO,并开展了原理性实验.在二极管的电压为480kV,电流为39kA条件下得到了功率为1.2GW,脉冲宽度为40ns的微波输出,功率转换 关键词： 磁绝缘线振荡器 高频特性 11模')" href="#">HEM₁₁模 开放腔     

Electron cyclotron resonance breakdown studies in a linear plasma system

Electron cyclotron resonance (ECR) plasma breakdown is studied in a small linear cylindrical system with four different gases — hydrogen, helium, argon and nitrogen. Microwave power in the experimental system is delivered by a magnetron at 2.45 ± 0.02 GHz in TE₁₀ mode and launched radially to have extra-ordinary (X) wave in plasma. The axial magnetic field required for ECR in the system is such that the fundamental ECR surface (B = 875.0 G) resides at the geometrical centre of the plasma system. ECR breakdown parameters such as plasma delay time and plasma decay time from plasma density measurements are carried out at the centre using a Langmuir probe. The operating parameters such as working gas pressure (1 × 10⁻⁵−1× 10⁻² mbar) and input microwave power (160–800 W) are varied and the corresponding effect on the breakdown parameters is studied. The experimental results obtained are presented in this paper.      

Hybrid Transmission Line for ECRH in the Helically Symmetric Experiment

The HSX oversized, mode-converting ECRH transmission line has been upgraded to a hybrid system to increase launched microwave power and reduce electrical arcing. Filtering of high-order, spurious modes ensures efficient coupling to a Gaussian beam for optimal electron heating. A Vlasov mode converter and two phase-correcting ellipsoidal mirrors convert the TE₀₂ gyrotron output mode to a symmetric, linearly polarized, microwave beam. A swappable twist reflector plate rotates beam polarization for 2nd-harmonic X-mode or fundamental O-mode ECRH. Long distances are traversed by coupling the beam to a dual-mode (TE₁₁ + TM₁₁), smooth, circular cross-section waveguide. This system has been successfully tested without arcing for 50 ms pulses and over 100 kW of launched power. Analysis of the microwave beam for 50 kW, 2 ms microwave pulses reveals agreement with predicted beam shapes at two beam locations. The new system has also demonstrated increased plasma stored energy for ECRH plasmas with equal launched power.     

高功率回旋行波管新型输出渐变段的设计

利用正余弦拟合的方法和半径渐变波导的耦合波理论设计出一种Ka波段TE01模回旋行波管新型输出渐变段。通过Matlab数值计算和HFSS仿真优化,研究了该新型渐变段的反射系数、传输参数、模式纯度、对杂模的耦合等性能指标。计算结果表明:在长度为80 mm、口径由14 mm变化到32 mm的情况下,在30～33 GHz该新型渐变段的传输参数大于-0.000 52 dB,反射参数小于-65 dB,模式纯度大于0.995,对TE02模和TE03模耦合在-40 dB以下。在等长度和等口径下,与Dolph-Chebyshev渐变段进行比较,结果显示在30～33 GHz内,新型渐变段比其传输参数更好、反射参数更小、模式纯度更高等。测试样品的冷测实验结果为在28～35 GHz范围内,其反射参数小于-30 dB,传输参数大于-0.3 dB。     

高功率微波在等离子体填充波导中的谐波产生

采用等离子体流体理论，研究了高功率微波在等离子体填充波导中的谐波产生，导出了非线性波动方程. 对二次谐波产生进行了数值计算与分析. 理论分析和数值计算表明，高功率微波将在等离子体填充波导中激发起谐波，TE_0n模式与TM_0n模式的基波都将激发起TM类型的谐波. 关键词： 高功率微波 谐波产生 等离子体填充波导     

非均匀扰动结构TE0n模式变换器研究

本文提出一种半径和周期双重扰动的非均匀圆波导TE_0n模式变换器. 通过耦合波理论(CWT)和数值优化方法对该模式变换器进行研究, 计算结果与电磁仿真软件基本一致. 与传统的均匀结构半径微扰模式变换器比较, 非均匀扰动结构TE_0n模式变换器可以在更少的波纹周期内实现高于均匀结构的模式转换效率, 95%功率转换绝对带宽增加150%, 器件长度减小接近一半. 本文的研究工作为设计轴向尺寸短、工作带宽大、 转换效率高的高功率回旋管外接模式变换器提供了重要参考.     

X波段高功率微波TE11模圆极化器

 基于圆波导TE₁₁模的模式简并特性和微波在椭圆波导中传输两个正交TE11模式相速不同的性质,研制了一种带有椭圆波导结构的圆波导TE₁₁模圆极化器。该圆极化器通过圆波导到椭圆波导的过渡段,将输入的线极化TE₁₁模式分成两个等幅、正交的TE₁₁模,然后调整椭圆波导长度,使得两个正交的TE₁₁模式的相位差为90°,实现了TE₁₁模式微波线极化到圆极化的转换。利用时域有限差分软件优化设计了该圆极化器,并按照优化的结构尺寸加工了一套实验装置进行了实验测试,测试结果表明：在工作频率9～10 GHz范围内,该圆极化器轴比小于1 dB,驻波比小于1.1,且功率容量大于1.6 GW。     

Experimental Study of a Slot Antenna Excited by a TE011 Mode Coaxial Cavity

A slot antenna is developed to excite the high harmonic waveguide mode for generating large-area plasmas. This antenna consists of a TE₀₁₁ mode coaxial cavity with the axial slots positioned on equal interval on the inner wall. The waves radiated from those slots can excite the high harmonic mode in the central area. With the azimuthal symmetric wave field of the TE₀₁₁ mode, the number of the slots can be chosen to match the field pattern of the high harmonic mode. In this report, the dispersion relation of the coaxial waveguide, the coupling scheme and the mode competition of the cavity are studied. A method has been successfully developed to suppress the TE₁₂₁ mode which is the most competing mode to the TE₀₁₁ mode.     

同轴虚阴极谐振效应研究

中国工程物理研究院应用电子学研究所的一些实验表明由阳极反射板、阳极网和阴极发射的电子束形成的环状虚阴极围成的准谐振腔是决定同轴虚阴极输出微波功率和传输模式的关键所在. 在二极管电压350kV，电流23kA条件下，获得了500MW的微波输出功率，能量转换效率约6.2％，工作频率3.3GHz，输出微波主要由TM₀₁模式和TE₁₁模式组成. 对同轴虚阴极的谐振效应进行了分析. 关键词： 高功率微波 同轴虚阴极 谐振腔 模式竞争     

Nonlinear analysis of a multi-cavity gyro-twystron

To preserve high gain, high efficiency and high power merits of gyroklystron, a gyro-twystron is designed using an electron beam with α(v_⊥/v_z) greater than unity. With a multi-cavity section of high gain, the length of the waveguide output section can be made shorter than the threshold length of the absolute instability without losing total system gain. Numerical simulations are carried out to analyze a ka-band gyro- twystron consisting of three TE₁₁₁ mode cavities and an output section of a TE₁₁ mode waveguide. Stability study is performed to ensure the tube without self-excited oscillations. With α=1.5, the 3-dB linear and saturated gain bandwidth in excess of 2 % can be obtained by stagger tuning for an 80 kV, 3 A electron beam with 5 % axial velocity spread. The maximum saturated gain is more than 55 dB at 33 % efficiency. By tapering the magnetic field of the last 2 cm of the interaction region, the efficiency can be increased to 43 % without degrading the bandwidth, which corresponds to an output power of 103 kW.     

Experimental Study of a High Power Coupler for a Tunable Cavity Formed by a Vane-Type Structure

In this study, a high power coupler designed for a tunable planar cavity is experimentally tested. The cavity consists of a periodical vane-type structure, of which the height of the vane can be mechanically adjusted so that the resonance frequency can be fine tuned. The cavity is designed to be operated at mode and resonant at 2.45 GHz. The high power coupler is composed of a rectangular waveguide and a cylindrical ceramic rod with tapered ends. One end of the ceramic rod is intruded into the gap between two vanes of the cavity. Through this coupler, the TE₁₀ mode of the rectangular waveguide is converted into the TE₁₁ mode of the ceramic rod and then couples to the TEM mode in the gap between vanes of the cavity. Experimental results show that a microwave power up to 5 kW can be effectively transmitted to excite the mode of the cavity . This cavity can be used to excite large area plasmas     

Analysis and Numerical Calculations of the Beam-Wave Interaction for Gyroklystron Amplifiers

A four-cavity gyroklystron was designed and optimized after analysis and calculation of RF system and magnetron injection gun, numerical simulations showed that the TE₀₁₁ mode gyroklystron achieved 280kW peak output power, 38% efficiency, 35dB saturated gain with 250Mhz bandwidth centered at 34GHz for a 68 kV, 11A electron beam. The numerical simulation results were used to build a Ka band high power gyroklystron amplifier. In this paper, analysis and numerical calculation results of the beam-wave interaction are presented. The influences of electron beam, RF system parameters, magnetic field, and input RF signal on output power, efficiency, bandwidth and gain are discussed.     

用于磁控管轴向辐射TE_(11)模式的紧凑型输出结构北大核心CSCD

提出了一种用于轴向输出相对论磁控管中具有TE_(11)辐射模式的紧凑型输出结构。该器件采用6谐振腔结构并工作在π模式上,通过合理设计谐振腔结构与输出圆波导之间过渡结构,模拟实现了圆TE_(11)模式微波的轴向输出。与传统衍射输出相对论磁控管相比,本文设计的轴向输出结构,不仅能在输出波导中获得更加纯净的微波模式,而且能减小磁控管的径向尺寸,使得系统更加紧凑化。初步的粒子模拟结果表明:当电压为280kV、磁场强度为0.5T时,该器件的工作频率为4.18GHz,输出功率为247.0 MW,功率转换效率达到21.9%。