EAST-NBI离子源电极打火分析及处理

强流离子源是EAST(Experimental Advanced Superconducting Tokamak)中性束注入器(Neutral Beam Injector,NBI)最关键的核心部件,其能达到的性能在很大程度上决定了EAST中性束注入器所能达到的指标。离子源在束引出时电极打火现象偶有发生,这对于离子源的正常运行有非常严重的影响,甚至危害离子源的寿命。本文结合离子源运行过程中的束引出实验波形和水流量热计(Water Flow Calorimetry,WFC)系统的测量数据得出等离子体发射面的束流光学系统一直处于非最佳聚焦状态是导致打火的原因,试通过优化高压投入时刻等离子体与高压的匹配,实现高压的稳定投入有效抑制打火现象的发生,并且给离子源加入硬件保护机制,为离子源安全稳定运行奠定基础。     

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.     

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...     

Results of Predictive Fokker?CPlanck Modelling of NBI Deuterons in ITER

First an analytical formalism is presented for calculating the source distribution of ions generated by neutral beam injection (NBI) in tokamak plasmas. A general NBI ion source term, applicable to studies in the phase space up to 6 dimensions, is provided for neutral beams with finite thickness and divergence. Further, using this source term for the envisaged NBI in ITER, we carry out 3D Fokker?CPlanck modelling of the steady-state deuteron distribution function of NBI produced fast deuterons relaxing on bulk plasma components. For two basic ITER scenarios we demonstrate the poloidal profiles of the beam deuteron density, of the NBI generated current as well as of the NBI power deposition to bulk electrons and ions. Further, we evaluate the capability of gamma and NPA diagnostics of NBI ions in ITER and demonstrate the sensitivity of the distributions of NBI generated ions to different ITER operation scenarios.     

基于多元线性回归模型的中性束质子比分析

中性束质子比的高低对其注入等离子体后的加热效果具有重要的影响。实验中,强流离子源的灯丝电压、弧压、进气量等宏观运行参数决定了中性束质子比的大小。以东方超环中性束注入测试台束引出实验为基础,利用多元线性回归模型对引出中性束质子比进行分析,建立了影响中性束质子比的预测方程,并对该模型的正确性进行了检验。结果表明,中性束质子比可利用以灯丝电压和弧压为自变量的多元线性回归模型进行分析,灯丝电压是影响质子比的关键参数,弧压次之。     

Commissioning of the first KSTAR neutral beam injection system and beam experiments

The neutral beam injection (NBI) system was designed to provide plasma heating and current drive for high performance and long pulse operation of the Korean Superconducting Tokamak Advanced Research (KSTAR) device using two co-current beam injection systems. Each neutral beam injection system was designed to inject three beams using three ion sources and each ion source has been designed to deliver more than 2.0 MW of deuterium neutral beam power for the 100-keV beam energy. Consequently, the final goal of the KSTAR NBI system aims to inject more than 12 MW of deuterium beam power with the two NBI for the long pulse operation of the KSTAR. As an initial step toward the long pulse (～300 s) KSTAR NBI system development, the first neutral beam injection system equipped with one ion source was constructed for the KSTAR 2010 campaign and successfully commissioned. During the KSTAR 2010 campaign, a MW-deuterium neutral beam was successfully injected to the KSTAR plasma with maximum beam energy of 90 keV and the L-H transition was observed with neutral beam heating. In recent 2011 campaign, the beam power of 1.5 MW is injected with the beam energy of 95 keV. With the beam injection, the ion and electron temperatures increased significantly, and increase of the toroidal rotation speed of the plasma was observed as well. This paper describes the design, construction, commissioning results of the first NBI system leading the successful heating experiments carried in the KSTAR 2010 and 2011 campaign and the trial of 300-s long pulse beam extraction.     

Electrical Parameter Measurement System of the Ion Source for EAST Neutral Beam Injector

Neutral beam injection (NBI) is recognized as one of the most effective means of plasma heating. A virtual instrument (VI) has been designed to provide electrical parameter measurement for the ion source of EAST-NBI. The VI is written using the National Instruments LabVIEW graphical programming language. All data acquisition (DAQ) is accomplished using ADLINK DAQ hardware interface and Task-oriented DAQ Driver. The VI can measure filament voltage, filament current, arc voltage, arc current and accelerating voltage etc. The data obtained from the VI are feedback of the ion source operation state and helpful to direct the operation parameter optimization of the ion source.     

Ion beam optics analysis and beam transmission simulation in the reflection magnet of the EAST NBI system

Detailed trajectories of the residual ion passing through a reflection magnet, which is installed in the Experimental Advanced Superconducting Tokamak (EAST) neutral beam injector (NBI) system to remove the residual ion from the beam path, are reported. Monte Carlo simulation has been performed to obtain estimations of the beam density on the high heat flux elements of reflection magnet. On magnet pole shielding, there are three high beam power density regions, resulting from beam line focus and corresponding to the full energy, half energy and third energy. These high heat flux regions will bring a serious challenge for steady-state operation. The simulation result indicates that the re-ionization loss is about 2.43% and the magnet pole shielding encounters a problem of beam line focus, which should be taken seriously during the steady-state operation.     

Design of the Prototype Negative Ion Source for Neutral Beam Injector at ASIPP

In order to support the design,manufacture and commissioning of the negativeion-based neutral beam injection(NBI) system for the Chinese Fusion Engineering Test Reactor(CFETR),the Hefei utility negative ion test equipment with RF source(HUNTER) was proposed at ASIPP.A prototype negative ion source will be developed at first.The main bodies of plasma source and accelerator of the prototype negative ion source are similar to that of the ion source for EAST-NBI.But instead of the filament-arc driver,an RF driver is adopted for the prototype negative ion source to fulfill the requirement of long pulse operation.A cesium seeding system and a magnetic filter are added for enhancing the negative ion density near the plasma grid and minimizing co-extracted electrons.Besides,an ITER-like extraction system is applied inside the accelerator,where the negative ion beam is extracted and accelerated up to 50 kV.     

HL-2AMW级中性束注入系统弧流电源设计

中性束注入是磁约束受控核聚变实验装置中加热等离子体最有效的方法之一。针对中国环流器2号中性束大功率离子源的特点,从系统功能、主电路拓扑结构、控制硬件及控制时序等方面对弧流电源进行设计。整个电源由低位移相交流调压、高压隔离降压变压器、整流滤波和电流快速转移电路4部分组成。IGBT与电阻串联组成电流快速转移阵列电路,与离子源并联,可实现电流单次或多次快速转移、参数远程设定,有效用于强流离子束的引出和保护。选用DSP和CPLD电路技术实现低位与高位控制器。实验数据显示,该电源最大输出为200kW/1000A,纹波小于2％,开关上升下降时间达μs级。目前,该电源已安全运行3年,可靠性高,完全满足装置离子源及系统要求,也可应用于其它等离子体技术应用场合。     

Design and Development of a Power Supply System for NBI Test Stand of EAST

A neutral beam injector (NBI) test stand was constructed to develop a multi-megawatt prototype ion source as an auxiliary heating system on experimental advanced superconducting tokamak. A power supply system for the NBI test stand components such as a set of dc power supplies for plasma generator, a dc high voltage power supply of a tetrode accelerator, a transmission line and a surge energy suppressor. Stable arc discharges of the plasma generator with hydrogen gases for 100 s long pulse have been produced by six Langmuir probes feedback loop regulation mode to control the arc power supply. The 4 MW hydrogen ion beam of 1 s is extracted with beam energy of 80 keV and the beam current of 52 A. The dc high voltage power supply for the plasma grid of the prototype ion source was designed to contribute maximum voltage of 100 kV and current of 100 A. The high voltage power output is continuously adjustable to satisfy with plasma physics experiment in operation frequency of 10 Hz. To prevent damage of the beam source at high voltage breakdown, core snubber using deltamax soft magnetic materials have been adopted to satisfy the input energy into the accelerator from the power supply can be reduced to about 5 J in the case of breakdown at 80 kV. For the transmission line, a disc shape multi cable coaxial configuration was adopted and which the dimension of the diameter is 140 mm at the core snubber. The major issues of discharge characteristics with long pulse and beam extraction with high power for the prototype ion source were investigated on the NBI test stand.     

Analysis of Power Deposition on Heat Load Components for EAST Neutral Beam Injector

Neutral beam injection is recognized as one of the most effective means of plasma heating. The target values of EAST Neutral beam injector (NBI) are beam energy 50–80 keV, injection beam total power 2–4 MW, beam pulse width 10–100 s. The beam power will deposit on the beam collimator due to the beam divergence and it will cause heat damage to heat load components, or even destroy the entire NBI system. In order to decrease the risk, the beam power deposited on heat load components should be assessed. In this article, the percent of power deposition on each heat load components has been calculated using Gaussian beam transmission model. Comparison of the results measured with water flow calorimeter and calculated results shows the beam transmission model has relative good agreement with real distribution. The results can direct the operation parameter optimization of EAST NBI.     

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.     

EAST中性束注入器稳态偏转磁铁的参数设计与估算研究

中性束注入器偏转磁铁是剥离束流中剩余离子的关键设备,它与剩余离子吞食器等内部部件构成了中性束注入器的束偏转系统。束偏转系统的性能对中性束注入器束流的品质及其束传输效率发挥着重要作用。本文根据EAST(Experimental Advanced Superconducting Tokamak,EAST)中性束注入器对束偏转系统的要求,对其偏转磁铁各性能参数进行了估算。为中性束注入器设计了一台用以剩余离子180°偏转的偏转磁铁。该偏转磁铁采用H型二极电磁铁结构;其磁极端面设计为138cm×47cm的圆角矩形结构;其线圈设计为每侧2饼,每饼2层,每层8根的串联结构,导线选用外方内圆空心铜导体,以满足偏转磁铁稳态运行的需要。该设计的偏转磁铁在370 A励磁电流条件下,可提供80keV氘离子束偏转所需的磁场。实验测试结果显示:500 A励磁电流稳态运行条件下,偏转磁铁线圈冷却水温升约21.5℃,该设计结构的偏转磁铁满足EAST中性束注入器满参数稳态运行和未来运行参数逐步提高的需要。     

Simulation of EAST off-axis neutral beam heating and current drive

The capability of off-axis neutral beam heating and current drive has been investigated with NUBEAM for Experimental Advanced Superconducting Tokamak (EAST). Three different approaches to realize off-axis Neutral Beam Injection (NBI) have been studied. Simulation results for on- and off-axis NBI are reported. The effects of the alignment of NBI relative to the magnetic field pitch on off-axis neutral beam heating and current drive are observed and discussed qualitatively. By comparing the numerical results, a most favorable off-axis NBI configuration is recommended. The capability to control sawtooth is also investigated by comparing locations of the q = 1 rational surface and the peak of the fast ion density profile.     

Overview of Development Status for EAST-NBI System

The neutral beam injection(NBI) system was developed on the Experimental Advanced Superconducting Tokamak(EAST) for plasma heating and current driving. This paper presents the brief history, design, development, and the main experimental results of the RD 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 diagnostic 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.     

Investigation of Arc Regulation of Hot Cathode Ion Source with Langmuir Probe

The neutral beam injector (NBI) is one of the main plasma heating methods for nuclear fusion devices. For the hot cathode high current ion source, the arc current and beam current tends to increase during the beam pulse. In order to gets long pulse beam extraction, the arc regulation technology is employed. The Langmuir probes are installed on the experimental advanced superconducting tokamak-NBI ion source, to feedback control the arc discharge and beam extraction. The experimental results show that, the long pulse of 100 s ion beam is extracted with beam energy of 30 keV with arc regulation. More the results are presented in this paper.     

Synchronous Output Control System of Two Megawatt Hot Cathode Bucket Ion Sources for NBI

Synchronous output of one beam line's two megawatt hot cathode bucket ion sources is required when Neutral Beam Injector(NBI) works on the Experimental Advanced Superconducting Tokamak(EAST).Neutral Beam Injector Control System(NBICS) realizes synchronous output and asynchronous output of two ion sources with network communication and hardware triggers.And the synchronous time can be set by operator.In synchronous mode,two megawatt hot cathode bucket ion sources can produce neutral beams at any relative time with higher energy than two sources' asynchronous output.Two megawatt hot cathode bucket ion sources' synchronous output makes an important contribution to NBI system of 4-8 MW with 10-100 s pulse length and provides more and better parameters for EAST physical experiments.     

基于CSS的NBI射频离子源控制程序设计

离子源是中性束注入器(Neutral Beam Injector,NBI)的关键子系统之一,根据射频离子源的实验和运行需求,本文设计了一套基于物理实验与工业控制系统(Experimental Physics and Industrial Control System,EPICS)架构的控制程序,实现对射频离子源实验和调试过程的远程监控功能。NBI射频离子源控制程序通过集成开发平台(Control System Studio,CSS)的交互界面开发模块(Best OPI Yet,BOY)实现友好的人机交互界面,使用Jython实现界面逻辑,支持服务器/客户端和EPICS两种通信架构。程序已经上线近半年,实验表明,射频离子源控制程序具备了放电模式设置、时序幅值设置、设备状态实时监控、采集数据实时波形显示等功能,满足了射频离子源实验的远程控制和数据可视化的需求。     

The Power Supply System of Ion Source for NBI

The power supply system of ion source for the Neutral Beam Injector (NBI) in the HT-7 superconducting tokamak is based on a single injector with one ion source that can deliver 700 kW of neutral beam power. Experiments and a discharges test on the ion source were successfully performed. In this paper, the circuit structures and features of every power supply are described and the results of the discharges test are presented.