ICRF功率传输系统中预匹配支节设计

在EAST装置内离子回旋共振加热(ICRF)系统中,天线与液态调配器之间传输线上的驻波电压幅值会因为负载阻抗的变化而变得很大,为此设计了ICRF功率传输预匹配支节。本设计采用解析法和Smith圆图法相结合的分析方式,在ICRF系统中安装了预匹配支节,并对其降压效果进行了测试。测试结果表明,安装预匹配支节之后,预匹配支节与液态调配器之间传输线上的驻波电压幅值得到有效降低,可作为优化ICRF功率传输系统功率传输性能的候选者。     

基于EAST装置上液态调配器系统的研究

液态调配器是用于离子回旋共振加热系统以代替传统活塞式调配器的一种新型阻抗匹配装置。通过对液态调配器工作原理的研究,设计了液态调配器的油路系统,采用计算机和可编程控制器对系统进行控制。同时,对液态调配器各支节匹配高度的计算方法进行了研究,提出了计算公式,并利用实验中测得的数据对计算公式进行了验证。经过两轮EAST实验使用证实,该系统完全满足设计要求。     

基于Labview的液态调配器的远程控制

通过对三支节液态调配器系统的分析,设计了一个由计算机远程监控5套三支节液态调配器的控制系统.硬件部分由PC机、数据采集卡、模拟输出卡、PLC、接口电路及其油路系统组成,软件部分采用虚拟仪器开发软件Labview设计,并采用自动和手动两种控制方式.通过数据采集卡来采集支节高度达到监测的目的,并通过Labview与PLC的串口通讯来控制上升回路、下降回路的开关从而控制液面上升、下降或停止,而高度调节的快慢则由模拟输出卡控制阀门开度大小来控制.与原系统相比,计算机监控系统控制更灵活、精确、高效和易于操作.     

EAST离子回旋系统液态相移器的理论设计

对EAST离子回旋系统液态相移器的原理进行了理论分析和计算,结果表明:利用液态相移器可产生相位差,从而可用离子回旋波进行电流驱动。另外,液态相移器也可与单支节液态调配器结合使用,构成传输线阻抗匹配系统。     

EAST离子回旋波加热快速阻抗匹配系统的研究

离子回旋波加热是EAST装置最重要的辅助加热方法,在实验中获得了明显的加热效果。射频功率源与天线负载之间阻抗匹配才能保证最大的加热功率输出。在射频加热实验中,等离子体参数的改变将会引起天线负载阻抗的快速变化,为应对这一情况研制出了快速阻抗匹配系统。本文采用解析法和计算机仿真相结合的分析方式,研制了该阻抗匹配系统的铁氧体匹配支节,并对其性能进行了测试。测试结果表明,快速阻抗匹配系统的时间响应速度明显优于传统匹配方式的,可作为实时匹配的候选者。     

调频对ICRH天线系统单铁氧体阻抗匹配效果的研究

采用传输线理论分析了离子回旋共振加热(Ion Cyclotron Resonance Heating,ICRH)天线耦合阻抗变化时(2～8Ω),频率反馈控制对ICRH天线系统单铁氧体调谐器阻抗匹配效果的影响.模拟结果表明:在一定条件下,优化设计铁氧体长度及天线与单铁氧体调谐器之间的机械长度(归一化长度约0.540),结...     

ICRF传输系统的优化数值分析

在开展离子回旋波加热实验时,高驻波电压是高功率射频传输过程中需要解决的主要问题之一。论文基于传输线理论,详细介绍了利用同轴短路或开路支节进行优化射频传输系统的方法,分析计算了支节的接入位置、支节长度、以及支节接入后的传输线电压分布。分析结果表明:传输线射频电压在支节接入后得以大幅降低,系统传输能力得到有效提高,降低了打火的概率。     

聚变驱动次临界堆双冷嬗变包层热工水力学参数设计与分析

聚变驱动次临界堆双冷嬗变包层是一个以氦气和液态金属LiPb为冷却剂,以嬗变核废料为主要目的的多功能包层。依据功率平衡模型对不同工况优化的基础上,对该包层热工系统参数进行了设计分析。采用三维商用计算流体力学程序对第一壁和高功率密度区中液态LiPb的流场进行数值模拟计算,给出了优化的典型热工水力参数。     

用样条函数作曲线拟合的一些问题

描述了确定三次样条曲线拟合参数的方法。参数包括节点数、节点位置和与系统误差相联系的权重。很好地给出了应用拟合准则的条件。     

阻抗匹配靶制备及靶参数精密测量

通过精密轧机轧制Al、Cu、Au等高纯金属箔片,采用精密微装配技术获得应用于激光状态方程实验所需的阻抗匹配靶。运用台阶仪和白光干涉仪分别对阻抗匹配靶进行靶参数精密测量。在“神光Ⅱ”上进行阻抗匹配的实验打靶,获得了相关靶型的实验图像。     

Theoretical Analysis of Triple Liquid Stub Tuner Impedance Matching for ICRH on Tokamaks

The impedance matching is crucial for continuous wave operation of ion cyclotron resonance heating(ICRH) antennae with high power injection into plasmas.A sudden increase in the reflected radio frequency power due to an impedance mismatch of the ICRH system is an issue which must be solved for present-day and future fusion reactors.This paper presents a method for theoretical analysis of ICRH system impedance matching for a triple liquid stub tuner under plasma operational conditions.The relationship of the antenna input impedance with the plasma parameters and operating frequency is first obtained using a global solution.Then,the relations of the plasma parameters and operating frequency with the matching liquid heights are indirectly obtained through numerical simulation according to transmission line theory and matching conditions.The method provides an alternative theoretical method,rather than measurements,to study triple liquid stub tuner impedance matching for ICRH,which may be beneficial for the design of ICRH systems on tokamaks.     

Design and Realization of Liquid Stub Tuner Control System

In microwave circuit and aerial system, impedance matching is very important. Liquid stub tuner is a new type of impedance matching device. In the HT-7 Tokamak Ion Cyclotron Resonance Heating ( ICRH ) system, we have already adopted liquid stub tuner to replacethe conventional stub tuner. It is urgent to develop a control system of the liquid stub tuner.This paper mainly introduces the design and realization of the liquid stub tuner control system ,and briefly introduces its three controlling functions: local control, remote control and computer control.     

Design of a New Type of Stub Tuner in ICRF Experiment

In the Ion Cyclotron Range of Frequency(ICRF) heating experiment,impedance matching is of great practical significance,because wide variations in antenna loading are observed within the discharge,in tokamaks operating in H-mode.A sudden decrease in antenna loading accompanying the L-mode to H-mode transition typically occurs on a timescale of a few millisec onds,as does the increase in loading at the H- to L-mode transition.Therefore,it is necessary to match dynamically in the transmission line between the generator output and the antenna input connections[1].A new type of stub tuner being developed utilizes the difference in radio-frequency wavelengths between gas and liquid due to different relative dielectric constants.The impedance matching can be adjusted in realtime in an attempt to track the variations in the antenna loading.Since there are no mechanically moving parts in the short ends of stub,the change can be more convenient and safe,moreover,it can withstand higher voltage without breakdown.this system device will be applied in the HT-7 superconductor Tokamak ICRF experiment.     

Real-time fast ferrite ICRF tuning system on the Alcator C-Mod tokamak

A real-time ion cyclotron range of frequencies (ICRF) antenna matching system has been successfully implemented on Alcator C-Mod. This is a triple-stub tuning system working at 80 MHz, where one stub acts as a pre-matching stub and the other two stubs use fast ferrite tuners (FFTs) to accomplish fast tuning. It utilizes a digital controller for feedback control (200 μs per iteration) using real-time antenna loading measurements as inputs and the coil currents to the FFT as outputs. The system has achieved and maintained matching for a large range of plasma parameters, including L-mode, H-mode, and plasmas with edge localized modes. It has succeeded in delivering up to 1.85 MW net rf power into H-mode plasmas at maximum voltage of 37 kV on the unmatched side of the matching system.     

Tunable biasing magnetic field design of ferrite tuner for ICRF heating system in EAST

Ion cyclotron range of frequency(ICRF) heating has been used in tokamaks as one of the most successful auxiliary heating tools and has been adopted in the EAST. However, the antenna load will fluctuate with the change of plasma parameters in the ICRF heating process. To ensure the steady operation of the ICRF heating system in the EAST, fast ferrite tuner(FFT) has been carried out to achieve real-time impedance matching. For the requirements of the FFT impedance matching system, the magnet system of the ferrite tuner(FT) was designed by numerical simulations and experimental analysis, where the biasing magnetic circuit and alternating magnetic circuit were the key researched parts of the ferrite magnet. The integral design goal of the FT magnetic circuit is that DC bias magnetic field is 2000 Gs and alternating magnetic field is±400 Gs. In the FTT, E-type magnetic circuit was adopted. Ferrite material is Nd Fe B with a thickness of 30 mm by setting the working point of Nd Fe B, and the ampere turn of excitation coil is 25 through the theoretical calculation and simulation analysis. The coil inductance to generate alternating magnetic field is about 7 m H. Eddy-current effect has been analyzed, while the magnetic field distribution has been measured by a Hall probe in the medium plane of the biasing magnet. Finally, the test results show the good performance of the biasing magnet satisfying the design and operating requirements of the FFT.     

Theory on dynamic matching with adjustable capacitors for the ICRF system of ASDEX Upgrade

The coupling of electromagnetic waves in the Ion Cyclotron Range of Frequencies (ICRF) is an important method to heat magnetically confined plasmas. Changing plasma conditions, which originate from processes like L-mode to H-mode transition or gas puffing, vary the load impedance of the ICRF antennas. To optimize the power transfer from the radio frequency (RF) generators to the antennas and consequently to the plasma, as well as to protect the RF sources against too high reflected power, a system that matches (i.e. transforms) the antenna input impedance to the impedance required by the generator is necessary. At ASDEX Upgrade this matching system consists of two stub tuners for each antenna, which match the antenna impedance for a value preset before the discharge. The length of the stubs cannot be changed fast enough to compensate plasma variations even on the moderate timescale of the confinement time in ASDEX Upgrade. The use of 3 dB-couplers allows operation even with varying load, at the cost of a reduced power to the plasma.When adjustable capacitors are applied in parallel to the stubs, dynamic matching becomes possible on the tens of ms timescale. The paper describes first the calculation of the required capacitance using transmission line theory. In a second model a minimum search algorithm finds, for a given antenna impedance, the length of the stubs needed for matching, now including the initial values of the capacitors. For the chosen pre-match point in the Smith chart, the range of impedances around this point is calculated for which the voltage standing wave ratio (VSWR) can be lowered below a minimum value by readjusting the capacitors within their maximum and minimum values. The matching range is thereby significantly larger than without the application of adjustable capacitors, at least with a frequency of 30 MHz and 36.5 MHz.     

Analysis of double stub tuner control stability in a phased array antenna with strong cross-coupling

Active stub tuning with a fast ferrite tuner (FFT) has greatly increased the effectiveness of fusion ion cyclotron range of frequency (ICRF) systems (50–100 MHz) by allowing for the antenna system to respond dynamically to changes in the plasma load impedance such as during the L–H transition or edge localized modes (ELMs). A high power waveguide double-stub tuner is under development for use with the Alcator C-Mod lower hybrid current drive (LHCD) system at 4.6 GHz. The amplitude and relative phase shift between adjacent columns of an LHCD antenna are critical for control of the launched n_|| spectrum. Adding a double-stub tuning network will perturb the phase and amplitude of the forward wave particularly if the unmatched reflection coefficient is high. This effect can be compensated by adjusting the phase of the low power microwave drive for each klystron amplifier. Cross-coupling of the reflected power between columns of the launcher must also be considered. The problem is simulated by cascading a scattering matrix for the plasma provided by a linear coupling model with the measured launcher scattering matrix and that of the FFTs. The solution is advanced in an iterative manner similar to the time-dependent behavior of the real system. System performance is presented under a range of edge density conditions from under-dense to over-dense and a range of launched n_||. Simulations predict power reflection coefficients (Γ²) of less than 1% with no contamination of the n_|| spectrum. Instability of the FFT tuning network can be problematic for certain plasma conditions and relative phasings, but reducing the control gain of the FFT network stabilizes the system.