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。     

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。     

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.     

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。     

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.     

EASTICRF天线电流带电磁分析

为了实现EAST托卡马克1000s以上的稳态先进模式运行的最终物理目标,两电流带双环共振(RDL)离子回旋共振（ICRF）天线被选择用来加热,电流带是ICRF天线关键部件,它通过近场区的耦合把能量传输到等离子体中。本文通过有限元方法对电流带在等离子体破裂和等离子体垂直位移事件两种工况下进行了电磁计算,给出了电流带感应电流密度大小分布情况、磁感应强度大小分布情况以及电流带所受的电磁力。利用电流带所受的电磁力作为载荷对电流带进行了结构分析,分析结果为验证电流带结构的可行性提供理论依据,分析方法对未来更高功率的ICRF天线电流带进行电磁分析具有一定的借鉴价值。     

Power Compensation for ICRF Heating in EAST

The source system covering a working frequency range of 24 MHz to 70 MHz with a total maximum output power of 12 MW has already been fabricated for Ion Cyclotron Range of Frequency(ICRF) heating in EAST from 2012. There are two continuous wave(CW) antennas consisting of four launching elements each fed by a separate 1.5 MW transmitter. Due to the strong mutual coupling among the launching elements, the injection power for launching elements should be imbalance to keep the k||(parallel wave number) spectrum of the launcher symmetric for ICRF heating. Cross power induced by the mutual coupling will also induce many significant issues,such as an uncontrollable phase of currents in launching elements, high voltage standing wave ratio(VSWR), and impedance mismatching. It is necessary to develop a power compensation system for antennas to keep the power balance between the feed points. The power balance system consists of two significant parts: a decoupler and phase control. The decoupler helps to achieve ports isolation to make the differential phase controllable and compensate partly cross power. After that, the differential phase of 0 or π will keep the power balance of two feed points completely. The first power compensation system consisting of four decouplers was assembled and tested for the port B antenna at the working frequency of 35 MHz. With the application of the power compensation system, the power balance, phase feedback control, and voltage standing wave ratio(VSWR) had obviously been improved in the 2015 EAST campaign.     

ICRF铁氧体快速匹配系统响应时间的研究

EAST搭建了铁氧体快速匹配系统来保证离子回旋波加热的功率输出。为了提高匹配系统的响应速度,通过理论计算与仿真分析相结合的方法,提出改善措施,实现了10 ms以内的系统响应时间。为搭建配备闭环控制的实时阻抗匹配系统奠定了基础。     

Observation of Central Toroidal Rotation Induced by ICRF on EAST

Core plasma rotation of both L-mode and H-mode discharges with ion cyclotron range of frequency(ICRF) minority heating(MH) scheme was measured with a tangential X-ray imaging crystal spectrometer on EAST(Experimental Advanced Superconducting Tokamak).Cocurrent central impurity toroidal rotation change was observed in ICRF-heated L-and H-mode plasmas.Rotation increment as high as 30 km/s was generated at ~1.7 MW ICRF power.Scaling results showed similar trend as the Rice scaling but with significant scattering,especially in L-mode plasmas.We varied the plasma current,toroidal field and magnetic configuration individually to study their effect on L-mode plasma rotation,while keeping the other major plasma parameters and heating unchanged during the scanning.It was found that larger plasma current could induce plasma rotation more efficiently.A scan of the toroidal magnetic field indicated that the largest rotation was obtained for on-axis ICRF heating.A comparison between lower-single-null(LSN)and double-null(DN) configurations showed that LSN discharges rendered a larger rotation change for the same power input and plasma parameters.     

Reference Design of ICRF Antenna for EAST

An antenna array suitable for plasma heating and current drive has been designed for the ion cyclotron resonance frequency range （ICRF） heating on the EAST superconducting tokamak. The ICRF heating is planned to operate in a frequency range of 30 MHz to 80 MHz and hence the antenna geometry is optimized for 55 MHz. The design is based on the conventional strap antenna element. The coupling properties of the antenna are calculated with a slab model of the plasma for the antenna simulation. The coupling code is extended for the analysis of the toroidal antenna array separated by septa.     

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.     

Current Status of ICRF Heating Experiments on EAST

Radio frequency (RF) heating in the ion cyclotron range of frequencies (ICRF) is one of the primary auxiliary heating methods for EAST. The ICRF system provides 6 MW power in primary phase and will be capable of 10 MW later. Three 1.5 MW ICRF systems in a frequency range of 25 to 70 MHz have already been in operation. The ICRF heating launchers are designed to have two current straps with each driven by a RF power source of 1.5 MW. In this paper a brief introduction of the ICRF heating system capability in EAST and the preliminary results in EAST are presented.     

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。     

Recent ICRF coupling experiments on EAST

Recent ion cyclotron resonance frequency(ICRF) coupling experiments for optimizing ICRF heating in high power discharge were performed on EAST. The coupling experiments were focus on antenna phasing and gas puffing, which were performed separately on two ports of the ion cyclotron resonance heating(ICRH) system of EAST. The antenna phasing was performed on the I-port antenna, which consists of four toroidally spaced radiating straps operating in multiple phasing cases; the coupling performance was better under low wave number ∣k_‖∣(ranging from 4.5 to 6.5). By fuelling the plasma from gas injectors, placed as uniformly spaced array from top to bottom at each side limiter of the B-port antenna, which works in dipole phasing, the coupling resistance of the B-port antenna increased obviously.Furthermore, the coupling resistance of the I-port antenna was insensitive to a smaller rate of gas puffing but when the gas injection rate was more than a certain value(1021 s~(-1)), a sharp increase in the coupling resistance of the I-port antenna occurred, which was mainly caused by the toroidal asymmetric boundary density arising from gas puffing. A more specific analysis is given in the paper.     

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.     

EAST ICRF天线驱动结构改进设计

针对ICRF天线原有的驱动结构由于无自锁而导致天线移动过程中无法精确定位的缺点,给出了两种新的驱动结构设计方案,两种方案主要由步进电机和涡轮蜗杆减速器组成,均具有启动速度慢,推、拉力大,能精确定位的特点。在设计过程中,对两种驱动结构的启动转矩、丝杠的强度和稳定性进行了校核,通过理论计算分析,两种驱动结构设计均满足设计要求。整个驱动结构改进设计方案和方法可为其他同类装置提供有益的借鉴。     

975 MHz高功率移相器的研制

移相器是直线加速器射频系统中的关键部件之一,为确保大功率加速器稳定运行,所用移相器需承受高射频功率的传输。基于改变传输线长度的移相方式,本文设计了通过电长度调节和3 dB混合耦合调谐的复合式结构,通过分析射频性能优化各部分结构,并对整个移相器结构进行模拟计算,研制了一种高功率移相器。实验测试结果表明,该移相器工作频率为975 MHz,在工作频率处驻波比为1.02,可实现0°～360°线性移相,整个移相范围内插入损耗小于0.45 dB。     

EASTICRF天线真空馈口热-结构分析

真空馈口是ICRF天线中的一个重要部件,它对ICRF天线起真空密封作用。鉴于真空馈口的重要性和安全性,运用有限元方法对两种形式的真空馈口进行了热和热-结构分析,给出了两种形式的真空馈口上的温度分布和应力分布。结果显示：镀银的真空馈口上的温度变化和应力均小于未镀银的真空馈口上的温度变化和应力,但两种形式的真空馈口上的应力均小于材料的许用应力。分析结果验证了真空馈口结构设计的可行性和安全性。     

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 the Vacuum Feedthrough for the EAST ICRF Antenna

Detailed design of the vacuum feedthrough for the Ion Cyclotron Radio Frequency (ICRF) antenna in EAST, along with an electro-analysis and thermal structural analysis, is presented. The electric field, the voltage stand wave ratio (VSWR) and the stresses in the vacuum feedthrough are studied. A method using the rings of oxygen-free copper as the cushion and macro-beam plasma arc welding is applied in the assembly to protect the ceramic from being damaged during welding. The vacuum leak test on the prototype of vacuum feedthrough is introduced.