A tunable magnetically insulated transmission line oscillator

A tunable magnetically insulated transmission line oscillator（MILO） is put forward and simulated. When the MILO is driven by a 430 k V, 40.6 k A electron beam, high-power microwave is generated with a peak output power of 3.0 GW and frequency of 1.51 GHz, and the relevant power conversion efficiency is 17.2%. The 3-d B tunable frequency range（the relative output power is above half of the peak output power） is 2.25–0.825 GHz when the outer radius of the slow-wave structure（SWS） vanes ranges from 77 mm to 155 mm, and the 3-d B tuning bandwidth is 92%, which is sufficient for the aim of large-scale tuning and high power output.

Investigation of an X-band magnetically insulated transmission line oscillator

An X-band magnetically insulated transmission line oscillator （MILO） is designed and investigated numerically and experimentally for the first time. The X-band MILO is optimized in detail with KARAT code. In simulation, the X-band MILO, driven by a 720 kV, 53 kA electron beam, comes to a nonlinear steady state in 4.0 ns. High-power microwaves （HPM） of TEM mode is generated with an average power of 4.1 GW, a frequency of 9.3 GHz, and power conversion efficiency of 10.870 in durations of 0-40 ns. The device is fabricated according to the simulation results. In experiments, when the voltage is 400 kV and the current is 50 kA, the radiated microwave power reaches about 110 MW and the dominating frequency is 9.7GHz. Because the surfaces of the cathode end and the beam dump are destroyed, the diode voltage cannot increase continuously. However, when the diode voltage is 400 kV, the average power output is obtained to be 700 MW in simulation. The impedance of the device is clearly smaller than the simulation prediction. Moreover, the duration of the microwave pulse is obviously shorter than that of the current pulse. The experimental results are greatly different from the simulation predictions. The preliminary analyses show that the generations of the anode plasma, the cathode flare and the anode flare are the essential cause for the remarkable deviation of the experimental results from the simulation predictions.

Magnetically insulated transmission line oscillator oscillated in a modified HEM_(11) 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 TEll-like circularly polarized mode; its polarization direction is decided by the rotation direction of the SWS.

HEM_(11) mode magnetically insulated transmission 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, the 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 TEll-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 kV450 kV, and the diode current is 37 kA-39 kA.

Experimental Study of Current Loss of Stainless Steel Magnetically Insulated Transmission Line with Current Density at MA/cm Level

A magnetically insulated transmission line （MITL） is used to transmit high power electric pulses in large pulse power systems. However, current loss is unavoidable, especially when the current density is up to 1 MA/cm. In the paper, the current loss of an MITL made of stainless steel, which is usually used in large pulse power generators, is experimentally studied, and possible mechanisms to explain the current loss of the MITL are analyzed and discussed. From the experimental results, the relationship between loss current density and input current density follows approximately a power law. The loss is also related to the configuration of the MITL.

Simulational Investigation of a High-Efficiency X-Band Magnetically Insulated Line Oscillator

Abstract The magnetically insulated line oscillator （MILO） is a gigawatt-class, coaxial crossed-field microwave tube, which is at present a major hotspot in the field of high-power mi- crowaves （HPM） research. In order to improve the power conversion efficiency and eliminate or at least minimize anode plasma formation in the load region and radio frequency （RF） breakdown in the slow wave structure （SWS） section, an X-band MILO is presented and inyestigated nu- merically with KARAT code. The design idea is briefly presented and the simulation results are given and discussed. In the simulation, HPM is generated with peak power of 3.4 GW, maximum electric field of about 1 MV/cm, and peak power conversion efficiency of 14.0%, when the voltage is 559.1 kV and the current is 43.2 kA. The microwave frequency is pure and falls in the X-band of 9.0 GHz. The theoretical investigation and the simulation results are given to prove that the anode plasma formation and the RF breakdown can be effectively avoided or at least minimized, respectively.

Low frequency acoustic properties of bilayer membrane acoustic metamaterial with magnetic oscillator

A bilayer membrane acoustic metamaterial was proposed to overcome the influence of the mass law on traditional acoustic materials and obtain a lightweight thin-layer structure that can effectively isolate low frequency noise. The finite element analysis（FEA） results agree well with the experimental results.It is proved that the sound transmission losses（STLs） of the proposed structures are higher than those of same surface density acoustic materials. The introduction of the magnetic mass block is different from the traditional design method, in which only a passive mass block is fixed on the membrane. The magnetic force will cause tension in the membrane, increase membrane prestress, and improve overall structural stiffness. The effects of the geometry size on the STLs are discussed in detail. The kind of method presented in this paper can provide a new means for engineering noise control.

Dynamic Model for the Z Accelerator Vacuum Section Based on Transmission Line Code

The transmission-line-circuit model of the Z accelerator, developed originally by W. A. STYGAR, P. A. CORCORAN, et al., is revised. The revised model uses different calculations for the electron loss and flow impedance in the magnetically insulated transmission line system of the Z accelerator before and after magnetic insulation is established. By including electron pressure and zero electric field at the cathode, a closed set of equations is obtained at each time step, and dynamic shunt resistance （used to represent any electron loss to the anode） and flow impedance are solved, which have been incorporated into the transmission line code for simulations of the vacuum section in the Z accelerator. Finally, the results are discussed in comparison with earlier findings to show the effectiveness and limitations of the model.

Investigation on current loss of high-power vacuum transmission lines with coaxial-disk transitions by particle-in-cell simulations

Coaxial-disk transitions can generate non-uniform magnetic fields and abrupt impedance variations in magnetically insulated transmission lines(MITLs),resulting in disturbed electron flow and non-negligible current loss.In this paper,3 D particle-in-cell simulations are conducted with UNPIC-3 d to investigate the current loss mechanism and the influence of the input parameters of the coaxial-disk transition on current loss in an MITL system.The results reveal that the magnetic field non-uniformity causes major current loss in the MITL after the coaxialdisk transition,and the non-uniformity decreases with the distance away from the transition.The uniformity of the magnetic field is improved when increasing the number of feed lines of a linear transformer driver-based accelerator with coaxial-disk transitions.The number of input feed lines should be no less than four in the azimuthal distribution to obtain acceptable uniformity of the magnetic field.To make the ratio of the current loss to the total current of the accelerator less than 2%at peak anode current,the ratio of the current in each feed line to the total current should be no less than 8%.

阶梯阴极型L波段MILO的实验研究

对阶梯阴极型L波段磁绝缘线振荡器（MILO）进行了实验研究。介绍了测试方法与测试系统；开展了阴极电子发射实验。发现阴极电子发射不均匀是对称结构MILO产生非对称微波模式的最关键的因素之一；并对二极管屏蔽环尺寸、扼流片半径、提取间隙等进行了研究。在电子束电压约420kV、电流33kA的条件下，得到了阶梯阴极型L波段MILO的高功率微波辐射功率为1．22～1．47GW，脉宽大于20ns，频率为1．21GHz。柬波转换效率约为10％。器件产生微波模式为TM01模。经过模式转换器后的辐射模式为TE11模。

高阶模抑制型MILO慢波结构高频特性分析(英文)

理论分析了高阶模抑制型磁绝缘线振荡器(MILO)慢波结构,推导了其各分区电磁场分布。通过对场分布的进一步分析可以发现,角向开槽使得原始MILO结构中的两个简并的HEM11模式去简并,分裂成为极化方向与开槽方向垂直或平行的两个模式;通过改变慢波结构叶片间开槽角向位置相对关系,可以破坏高阶模式之间π模谐振关系,从而抑制高阶模式的起振,使器件稳定工作在基模。

L波段MILO低真空下工作特性的粒子模拟与实验研究

通过实验和粒子模拟相结合的方法对L波段MILO在低真空度下的工作特性进行了研究。实验和模拟中都观察到了低真空情况下MILO的功率增强和频率升高,在2 Pa内,粒子模拟中没有观察到脉冲缩短现象,实验上脉宽略有下降,但是辐射微波单脉冲能量增大,MILO工作性能在低真空下有一定提高。研究发现适量等离子体填充同样可以改善MILO工作性能。

P波段混合型MILO的粒子模拟

结合负载限制型磁绝缘线振荡器(MILO)和渐变型MILO的特点提出并设计了P波段混合型MILO的结构,主要以负载限制型MILO结构作为雏形,将其内部仅含有的1根提取叶片用3根长度渐变的慢波叶片组成的渐变段替换。该结构可更好地实现束波相互作用,并使提取间隙电场与MILO输出同轴结构处的电场达到更好的匹配,增加微波输出功率。器件纵向总长度为47 cm,外筒直径为44 cm。优化后的2.5维全电磁粒子模拟结果表明:在二极管工作电压550 keV、电流约57 kA的情况下,输出微波的中心频率为640MHz,平均功率为4.27 GW,束波转换效率为13.6%,器件4 ns时起振,6 ns达到饱和,且微波输出功率十分稳定,最终输出微波模式为TEM模。

四腔阶梯阴极L波段MILO数值模拟

为了提高器件微波输出功率和功率转换效率,设计了一种四腔结构L波段阶梯阴极磁绝缘线振荡器,运用开放腔高频分析方法得到了谐振频率和高频电场分布,并计算得到了器件的有载品质因数。运用粒子模拟方法对器件进行研究,典型的粒子模拟结果为:在束压为578kV和束流为46.5kA条件下,得到功率为5.1GW的微波输出,工作频率为1.21GHz,功率转换效率为18.9%。最后讨论了电压变化对器件的功率转换效率和频率的影响:器件工作频率受电压变化影响较小;功率转换效率受电压影响较大,在电压为667kV时效率达到最大值20.45%。

Frequency Tunability and Slow-Wave Characteristics of a High-Efficiency Ridged MILO

A high-efficiency ridged magnetically insulated transmission line oscillator (RMILO) is proposed and investigated theoretically and numerically in this paper. In the RMILO, ridge-disk vanes are introduced to enhance the power efficiency. Theoretical investigation shows that the ridge-disk can enhance the coupling impedance of the slow-wave structure (SWS), and so enhance the power efficiency. Moreover, the ridge has a weak influence on frequency, so, it influences little on the tunability of the MILO. In simulation, when the applied voltage is increased to 807 kV, the RMILO can get the 3 dB tunable frequency range with 7.6 - 13.9 GHz and the 3 dB tuning bandwidth with 58.6% which has an increase of 27.6% compared with the conventional MILO. So, the tuning performance of the RMILO is more superior. Besides, the RMILO gets the maximum output power of 7.1 GW, the corresponding power efficiency is 22.6% and the frequency is 1.400 GHz. Furthermore, when the applied voltage is increased to 807 kV, high-power microwave with a power of 13.5 GW, frequency of 1.400 GHz, and ef?ciency of 24.5% is generated, which has an increase of 20.2% compared with the conventional MILO. The simulation results con?rm the ones predicted by theoretical analysis.

15 MA Z箍缩装置真空磁绝缘传输线鞘层电子流分析

基于建立的15 MA Z箍缩装置等效电路模型,获得了外层磁绝缘传输线(magnetically-insulated transmission line,MITL)鞘层电子流分布规律:从时间上看,鞘层电子流幅值先减小、后增大,波形呈“马鞍”型;从空间上看,鞘层电子流沿着功率流方向逐渐减小.分析了MITL参数,包括恒阻抗段真空阻抗、恒间隙段间距,以及柱孔盘旋面位置半径对MITL末端鞘层电子流的影响.计算结果显示:MITL末端鞘层电子流受MITL末端阻抗和柱孔盘旋面位置半径的影响较大.当15 MA装置四层MITL并联真空阻抗从0.42Ω增大到0.84Ω时,在负载聚爆前5 ns时刻,MITL末端鞘层电子流从184.7 kA降低至106.9 kA,负载峰值电流减小约0.5 MA.

绝缘子清洗机器人静磁场分析及优化

绝缘子清洗机器人在绝缘子串上开展清洗作业时,可能会影响输电线路上的静磁场环境,导致周围静磁场产生变化,其磁场强度可能越限。因此需要开展机器人绝缘子串清洗作业的静磁场分析。针对机器人清洗110 kV输电线路上的水平悬式绝缘子情况,基于ANSYS有限元分析软件分析机器人到达绝缘子串3处位置时的静磁场强度大小以及分布情况;同时为了降低机器人对周围静磁场环境的影响,对机器人的制作材料进行了优化。静磁场分析结果表明,在110 kV输电线的输送功率为10~50 MW范围内,机器人移动到绝缘子串3处位置时的磁感应强度均达到了限值;比较了铝质材料和镀铜材料的静磁场强度,结果表明,机器人制造材料更换为磁导率相对较低的镀铜材料时,可以减少周围磁场强度的大小,缩小机器人移动到不同位置时的磁场强度相对变化量,降低机器人对输电线路电磁环境的影响。

紧凑型L波段磁绝缘线振荡器的实验研究

设计加工了一个紧凑型L波段磁绝缘线振荡器(MILO)并进行了实验研究。该MILO具有一个新型收集极和一个新型模式转换器,射频扼流腔减为一个,同时将阴极杆设计成变阻抗结构,该MILO由一台自建的600kV,8Ω,100ns加速器SPARK 01驱动。在二极管电压为515～538kV,二极管电流为58～61kA的条件下,该MILO在实验中获得了1.76～1.78GHz,2.2～2.5GW的TM01模高功率微波辐射,功率转换效率为7.3%～7.9%。在30ns的有效电压脉宽下,实验中测得微波脉冲半高宽为15ns。实验结果与模拟结果符合得较好。

强风区750kV复合绝缘子抗风性能研究

在我国西北部的特高压输电线路中,复合绝缘子被广泛应用,但途经＂三十里风区＂的750 kV输电线路,在运行不到一年时间内,就出现大量绝缘子伞裙根部断裂故障。强风条件下伞裙发生持续稳定的强烈摆动,最终导致硅橡胶材料疲劳断裂。该文首先利用有限元软件分析流体中复合绝缘子的受力情况,研究绝缘子各部位的风压分布和伞裙附近的流场特点;其次提出一套复合绝缘子风洞实验方法,研究两支典型750 kV复合绝缘子在25～60 m/s风速范围内的伞裙动态过程。风洞实验研究发现,在V型串的悬挂方式下,背风侧绝缘子串伞裙相对迎风侧绝缘子更易起振,且芯棒与来流夹角的变化对其起振风速影响显著,最不利来流迎风角在50°;绝缘子的停振风速相对于起振风速降低最高可达17.6%;通过不同风速下伞裙摆动频率和幅度研究,发现随风速的升高,摆动频率较稳定,但摆动幅度会明显提高,伞裙摆动幅度最大可达伞间距的79%。

共顶点同轴圆锥形及圆盘形传输线的电参数计算公式

用安培环路定理、高斯定理推导了共顶点同轴圆锥形及圆盘形两种重要的理想传输线电参数的计算公式,给出了电场、电感、电容及阻抗的解析表达式或数值求解方法;用实例验证了推导的公式和介绍的方法;应用验证后的公式或方法对一个设计进行了估算,得到了合理的结果。