Discharge Characteristics of Large-Area High-Power RF Ion Source for Positive and Negative Neutral Beam Injectors

A large-area high-power radio-frequency（RF） driven ion source was developed for positive and negative neutral beam injectors at the Korea Atomic Energy Research Institute（KAERI）. The RF ion source consists of a driver region, including a helical antenna and a discharge chamber, and an expansion region. RF power can be transferred at up to 10 kW with a fixed frequency of 2 MHz through an optimized RF matching system. An actively water-cooled Faraday shield is located inside the driver region of the ion source for the stable and steady-state operations of high-power RF discharge. Plasma ignition of the ion source is initiated by the injection of argongas without a starter-filament heating, and the argon-gas is then slowly exchanged by the injection of hydrogen-gas to produce pure hydrogen plasmas. The uniformities of the plasma parameter,such as a plasma density and an electron temperature, are measured at the lowest area of the driver region using two RF-compensated electrostatic probes along the direction of the shortand long-dimensions of the driver region. The plasma parameters will be compared with those obtained at the lowest area of the expansion bucket to analyze the plasma expansion properties from the driver region to the expansion region.

Estimation of Ion Beam Trajectories for a Slot Aperture Accelerator of Long-Pulse Ion Source in Neutral Beam Injector

A neutral beam injection (NBI) system has been developed and is being tested for an Experimental Advanced Superconducting Tokamak (EAST) device. The NBI system needs to be employed for an auxiliary heating and current drive of EAST plasmas. The first long pulse ion source (LPIS-1) has been installed in the neutral beam test bed (NBTB) system, and the performance is being tested in the NBTB. The LPIS-1 consists of a magnetic bucket plasma generator with multipole cusp-fields and a set of tetrode accelerators with slit-type apertures (a transparency of 60%). The ion beam trajectories of the accelerator column are estimated for the LPIS-1, including an original structure, with the change of slit aperture distance, plasma grid shape, grid gap distance, and voltage ratio between a plasma grid and a gradient grid using the IGUN code. This kind of calculation for the ion beam trajectory may be useful for the estimation of beam extraction characteristics and the direction of accelerator upgrade or modification, prior to the experiments of ion beam extraction.

Thermal analysis of EAST neutral beam injectors for long-pulse beam operation

Two sets of neutral beam injectors(NBI-1 and NBI-2) have been mounted on the EAST tokamak since 2014. NBI-1 and NBI-2 are co-direction and counter-direction, respectively. As with indepth physics and engineering study of EAST, the ability of long pulse beam injection should be required in the NBI system. For NBIs, the most important and difficult thing that should be overcome is heat removal capacity of heat loaded components for long-pulse beam extraction. In this article, the thermal state of the components of EAST NBI is investigated using water flow calorimetry and thermocouple temperatures. Results show that(1) operation parameters have an obvious influence on the heat deposited on the inner components of the beamline,(2) a suitable operation parameter can decrease the heat loading effectively and obtain longer beam pulse length, and(3) under the cooling water pressure of 0.25 MPa, the predicted maximum beam pulse length will be up to 260 s with 50 keV beam energy by a duty factor of 0.5. The results present that, in this regard, the EAST NBI-1 system has the ability of long-pulse beam injection.

Achievement of 1000 s plasma generation of RF source for neutral beam injector

A radio frequency(RF) ion source was developed for neutral beam injector in Institute of Plasma Physics, Chinese Academy of Sciences(ASIPP). A cylindrical driver based RF plasma source was tested and optimized for long pulse operation. Recently, the plasma source achieved 1000 s stable plasma discharge with RF power of 35 k W and source pressure of 0.7 Pa for the first time.The heat loading on each of driver components such as the Faraday shield(FS), RF coil and expansion chamber was measured by the water flow calorimeter system. The experiment results showed that FS is the component with highest heat loading and the heat loading on FS was about 65.8% of total heat loading on source. The details of the long pulse operation of RF plasma source are presented in this paper.

R&D progress of high power ion source on EAST-NBI

The neutral beam injector （NBI） system was designed and developed mainly for the plasma heating on the Experimental Advanced Superconducting Tokamak （EAST）. The high power ion source is the key part of the NBI. A hot cathode ion source was used on the EAST-NBI. The ion source was conditioned on the ion source test bed with hydrogen gas and achieved the designed parameters. The deuterium gas was used when it moved to the EAST-NBI. The main performance of the ion source on EAST is presented in this paper. The highest beam power of 4.5 MW in NBI-1 and 2.75 MW in NBI-2 was achieved. The total neutral beam power is about 4.5 MW. The long pulse beam of 100 s is injected into the EAST plasma too.

First results of negative ion extraction with Cs for CRAFT prototype negative beam source

In order to understand the physics and pre-study the engineering issues for radio frequency(RF)negative beam source,a prototype source with a single driver and three-electrode accelerator was developed.Recently,the beam source was tested on the RF source test facility with RF plasma generation,negative ion production and extraction.A magnetic filter system and a Cs injection system were employed to enhance the negative ion production.As a result,a long pulse of 105 s negative ion beam with current density of 153 A m-2 was repeatedly extracted successfully.The source pressure is 0.6 Pa and the ratio of co-extracted electron and negative ion current is around0.3.The details of design and experimental results of beam source were shown in this letter.

EAST强流离子源电源系统的初步测试运行

测试NBI大功率强流离子源的综合测试台正在建设,已研制了离子源等离子体发生器电源系统、等离子体电极高压电源及梯度极分压器、抑制极负高压电源等电源系统,以及高压传输线及缓冲器,在测试台上开展了对EAST中性束注入器第一台兆瓦级强流离子源样机进行整体电源系统测试和离子源起弧放电的初步测试,完成了离子源电源系统初步性能测试及系统整体联调,给出了各套电源系统测试运行达到的参数指标,在兆瓦级强流离子源样机上获得了首次离子源起弧放电的实验结果。

EAST中性束注入器研制进展

EAST(Experimental Advanced Superconducting Tokamak)作为世界上第一个全超导非圆截面托克马克,其目标是研究1 000 s的长脉冲稳态运行的前沿性物理问题,要达成这一目标,必须有高功率电流驱动和辅助加热系统以实现EAST装置的高参数稳态运行。中性束注入(Neutral Beam Injection,NBI)加热是等离子体辅助加热和维持最有效的手段之一,为此一套注入功率4–8 MW、脉冲宽度10–100 s的中性束注入系统于2010年开工建设,并于2014年实现了对等离子体的加热和驱动。本文主要展示了EAST中性束注入器的最新进展,从长脉冲束引出和高功率束引出两个方面介绍了EAST中性束注入器综合测试台的最新实验结果,结果表明在束功率和脉冲宽度方面已经达到或超过设计指标。

Overview of Development Status for EAST-NBI System

The neutral beam injection （NBI） system was developed on the Experimental Ad- vanced Superconducting Tokamak （EAST） for plasma heating and current driving. This paper presents the brief history, design, development, and the main experimental results of the R＆D of neutral beam injector on the test bed and on EAST. In particular, it will describe： （1） how the two beamlines with a total beam power of 8 MW were developed; （2） the design of the EAST-NBI system including the high power ion source, main vacuum chamber, inner components, beam diag- nostic system and sub-system; （3） the experimental results of beamline-1 on the summer campaign of EAST in 2014 and, （4） the status of beamline-2 and the future plan of EAST-NBIs.

强流离子源灯丝电源设计与分析

灯丝电源是中性束注入器等离子体发生器电源系统的重要组成部分,为了满足其低电压大电流输出特性要求,提出了带平衡电抗器双反星形整流电路的拓扑结构的电源设计方案。该拓扑结构与三相桥式整流电路相比较在采用相同器件下可达到更高功率,减少交流侧输入电流谐波并提高功率因素。分析了该拓扑结构下整流输出特性和所含的谐波分量,根据设计指标计算了整流变压器和平衡电抗器的相关参数,最后通过仿真和实验结果验证了这一拓扑结构的可行性。

中性束注入器离子源测试台可编程逻辑控制系统

为实现对离子源测试台系统现场设备的实时监控,设计了一套基于现场总线(Profibus)通讯协议的可编程逻辑控制器(PLC)系统。根据综合测试台测控要求确定PLC系统硬件配置,组建单主站Profibus-DP网络实现高速分布式I/O系统。该系统实时监测现场设备状态并与中性束注入总控实时交换数据,协调控制现场设备按序稳定运行。全图形化的人机操作界面实现了系统运行的可视化操作,数据的实时存储和显示为物理操作人员提供了实验分析依据。整个系统控制稳定可靠,重复性好,兼容性及扩展能力强。

中性束注入强流离子源放电电源及其时序控制

中性束注入是磁约束核聚变装置中加热等离子体最有效方法之一。为了建设完善中国环流器2号A装置1MW中性束注入器系统,对大功率强流离子源所需的弧放电电源、束线引出电源、辅助电源及控制时序等进行了设计研制。设计中采用了DSP控制技术、电流快速转移技术、IGBT串联调制器技术、高频开关电源技术、磁缓冲器技术以及工业以太网等诸多技术。该系统已经稳定地运行3a时间,开展了高参数注入实验,注入装置的中性束功率接近1MW,瞬时离子束功率超过2MW,脉冲宽度达到1s,在国内首次使等离子体离子温度超过2×107°C。实验结果表明:所研制的电源及控制系统能有效地用于强流离子束的引出和保护,完全满足HL-2A装置辅助加热系统的要求。

NBI双潘宁离子源参数的静电探针测量

介绍了静电探针在22cm双潘宁离子源中心等离子体参数测量中的应用。测出了探针的伏安特性曲线,由该曲线求出在弧流为200 A时,电子温度约为6.0 eV,密度约为2×1012cm-3,这对于调整放电控制条件,获得高效率大功率的离子源有重要的参考价值,并且对于今后实现强而且均匀的中性束束流的引出也有着重要意义。

基于数字控制大功率整流电源的设计

针对典型的大功率整流电源,提出了一种基于数字控制的设计方案。通过对大功率中性束注入器离子源灯丝电源的方案设计和实验结果,验证了数字控制方案的可行性与优越性。由于数字控制方案的应用,使得灯丝电源的设计更加智能化和简单化,为相关的应用场合提供了参考。

强流双潘宁离子源弧特性研究

针对22cm双潘宁离子源,研究了其弧流与放电调节参数的关系以及二次进气的效果,确定了拉长弧流脉宽、提高弧流强度与稳定性、达成离子源合适工作状态的措施,为获得高品质的弧流提供了依据。离子源弧特性测试研究结果对提高强流离子源的工作性能以实现NBI系统强流准稳态运行有重要的指导意义。

中性束注入RF负离子源的发展及其特性研究

相对于灯丝源,RF源由于不需要维护现在已经成为灯丝源的一个令人感兴趣的替代品I,PP伽兴研究所对RF负离子源的大量的研究工作直接导致了ITER选择RF负离子源作为ITER堆中性束注入系统的离子源.这项工作使用三个实验装置:BATMAN、MANITU及RADI,这三个实验装置沿三条线平行的进行不同的研究.实验结果表明IPP的RF负离子源已经达到甚至超过了ITER的要求.

MNI—1U中性注入器高压长脉冲稳定电源研制

本文介绍一种为MNI-1U中性注入器研制的大功率长脉冲高压稳定电源。电路的技术指标为:输出脉冲电压50kV,脉冲电流30A,脉冲宽度50ms,上升下降时间小于25μs,平顶稳定度优于0.5％,调整响应时间30μs。当作直流高压稳压和稳流电源使用时,输出电压1-80kV,电流0.5—5A,电压或电流的稳定度可优于0.1％

聚变堆中性束注入系统的电偏转器概念设计

中性束注入是磁约束核聚变研究重要的辅助加热和电流驱动手段。由于负离子源中性束注入系统束能量高、束斑大,电偏转已经成为剩余离子剥离的首选方案,其剩余离子剥离设备被称为电偏转器。电偏转器作为实现束流中性化的核心设备,其性能决定了中性束注入系统的工作效率。本文提出了聚变堆主机关键系统研究中负离子源中性束注入系统电偏转器的概念设计方案,通过理论计算和束流沉积模拟初步确定了电偏转器的结构和其表面较为均匀的热负荷分布,完成了电偏转器的参数设计,此设计可为电偏转器进一步的工程设计提供设计参考。

中性束注入器用串联高压缓冲器优化设计

为了优化中性束注入器(NBI)用高压缓冲器的布局,分析了缓冲器结构设计参数和缓冲器性能的相互关系,并通过等效电路仿真模型修正了缓冲器放电峰值电流经验公式,得到了不同激励信号下串联高压缓冲器在高频脉冲放电情况下的特性,最后,在高压缓冲器理论分析和仿真分析的基础上,对设计的非晶缓冲器和Deltmax缓冲器串联高压测试件进行了短路放电测试,得到了短路放电瞬间串联缓冲器的分压和回路的放电电流。放电实验结果表明,黑色非晶缓冲器感应电压频率响应比较快,Deltmax缓冲器可以消耗更多的故障电流能量,非晶缓冲器和Deltmax缓冲器这2种不同直流缓冲器的串联能够有效地抑制高压直流故障短路电流并吸收故障电能。

HL-2M装置中性束离子源束光学红外成像实验研究

为了研究HL-2M装置中性束注入(NBI)加热用的80k V/45A/5s热阴极离子源束光学特性,采用红外电荷耦合元件(CCD)成像技术,测量离子源引出粒子束轰击量热靶板产生的温度分布,得到束功率密度空间分布区间特征参数1/e半宽度。在NBI热阴极离子源调试平台上,扫描离子源的放电和引出参数,利用CCD红外热像仪获得了对应参数下量热靶上的束功率密度分布。实验结果表明,HL-2M装置NBI加热系统80k V/45A离子源可用的导流系数范围为0.7~1.5?P。同样导流系数下,梯度电极与等离子体电极的分压比较高时,引出束流的半宽度较小。