EAST托卡马克电荷交换复合光谱诊断的绝对强度标定

电荷交换复合光谱(Charge e Xchange Recombination Spectroscopy,CXRS)诊断系统主要用于等离子体旋转速度和离子温度的测量。CXRS诊断的另外一个重要应用是通过测量光谱的绝对强度来确定杂质离子的密度,因此需要对系统进行绝对强度标定。在实验前通过精确校准过且各个波长强度已知的积分球光源对系统进行初步的标定;在实验过程中又利用托卡马克装置中等离子体自身产生的轫致辐射对系统的强度标定进行了进一步的检验。通过比较轫致辐射强度的实验测量值和理论计算值,可以发现两种方法得到的结果虽然存在一定的误差,但是它们的趋势是一致的。实验结果表明,利用轫致辐射进行绝对强度标定是可行的。     

HL-Ⅰ装置等离子体真空紫外光谱研究

本文叙述了在HL-1装置上做的真空紫外区(30～200nm)光谱实验。用微通道板象增强器摄出了光谱,对光谱进行了辨认和分析。用光电法测量了谱线随时间的变化和缩小孔栏时的杂质变化情况,观察了等离子体发生小破裂时出现的光谱现象,对杂质的来源及其某些性质进行了分析研究。用两条CIV谱线强度比测出了放电初期的电子温度。     

HL-I装置等离子体真空紫外光谱研究

本文叙述了在HL-1装置上做的真空紫外区(300—2000)光谱实验。用微通道板象增强器摄出了光谱,对光谱进行了辨认和分析。用光电法测量了谱线随时间的变化和缩小孔栏时的杂质变化情况,观察了等离子体发生小破裂时出现的光谱现象,对杂质的来源及其某些性质进行了分析研究。用两条CIV谱线强度比测出了放电初期的电子温度。     

EAST全超导托卡马克高分辨率EUV光谱仪诊断系统

EAST全超导托卡马克装置上建立一套极紫外(EUV)光谱诊断系统,用于高温等离子体高电离态杂质线辐射研究.该系统利用1200 l/mm凹面变线距全息光栅作为分光元件,工作波段50-500(A),波长分辨率Δλ-0.16(A)(186.6?),时间分辨为20 ms,空间观测范围为0-450 mm,基本覆盖EAST全超导托...     

EAST托卡马克激光吹气杂质注入系统控制系统设计及测试

开展托卡马克等离子体中杂质输运与杂质控制研究对于提升等离子体约束性能与保障装置安全有重要意义。为了在EAST(Experimental Advanced Superconducting Tokamak)托卡马克装置上开展杂质输运研究,需要发展一套用于注入示踪杂质粒子的激光吹气（Laser Blow-off,LBO）微量杂质注入系统。本文描述了一种用于EAST托卡马克装置上LBO系统的控制系统设计过程与测试结果。该系统采用了全新的自动控制流程,使得系统可以重复、定量地向EAST等离子体注入不同元素的示踪杂质粒子。该设计通过STM32单片机系统实现对聚焦透镜位移、激光器被触发时刻的准确控制,且激光光斑直径可调,以改变杂质注入量。测试结果显示,系统能快速检测到外触发信号并实现精确定时,激光光斑聚焦位置误差小于0.40 mm,达到激光吹气杂质注入实验要求。本研究对在EAST装置上开展等离子体杂质输运研究具有重要意义。     

利用真空紫外光谱研究HL-1装置杂质浓度(英文)

叙述了利用真空紫外光谱确定HL-1装置杂质浓度的方法,详细报告了用于解释光谱测量的杂质输运模型SITCODE。此模型可以计算各个电离态杂质的密度分布以及由杂质引起的电离,轫致辐射和激发等形式的能量损失,该模型是一维的结合新经典与反常输运的杂质输运模型,用模拟的线强度获得了氧的浓度并估计了氧杂质引起的辐射功率,较了不同电子温度和不同反常扩散系数的氧离子密度的径向分布。基于SITCODE,开发了一种杂质浓度的快速分析方法,在每次放电后利用测量的OⅥ103.2nm。线强度可计算出氧浓度,实现杂质浓度的实时分析。对HL-1托卡马克在不同放电情况下杂质浓度进行了测量,且对杂质输运情况进行了研究。     

托卡马克弯晶谱仪双晶体结构应用的初步研究

X射线弯晶谱仪作为托卡马克装置等离子体温度和旋转速度等参数诊断测量的重要手段之一,通常利用单晶体衍射分光来测量某种特定杂质的特征谱,这也限制了弯晶谱仪所能测量的等离子体温度范围。为解决更高温度等离子体测量问题,有效提高目前弯晶谱仪诊断系统温度测量范围,用双晶体代替原有单晶体,通过选择合适的晶体和Bragg衍射角组合,利用同一个探测器同时测量类氢和类氦的氩离子光谱,实现更高更宽温度范围测量。本文就东方超环(Experimental Advanced Superconducting Tokamak,EAST)弯晶谱仪双晶体应用方面的设计和技术实现进行了阐述,并首次在EAST装置上成功实现了氩离子类氦和类氢谱线的测量,利用类氦线和类氢线拟合得到的氩离子温度非常接近,验证了双晶体结构的可行性。     

EAST辐射偏滤器运行模式下等离子体杂质浓度评估方法

通过在偏滤器区域充入适量氖气（Ne）或氩气（Ar）,东方超环（Experimental Advanced Super-conducting Tokamak,EAST）托卡马克装置实现了辐射偏滤器运行模式。在辐射偏滤器运行模式下,靶板热负荷显著降低,有效缓解了高能粒子流对偏滤器靶板的损伤。但是在偏滤器区域充入过量杂质气体时,杂质粒子会沿着磁力线进入主等离子体,影响主等离子体的约束性能,甚至导致等离子体破裂。因此,有必要研究偏滤器区域等离子体杂质浓度的估算方法,分析充入杂质气体时该区域杂质的定量变化,以此来评估充入的杂质气体对芯部等离子体约束性能的影响。本文针对不同的杂质种类,建立了不同的杂质浓度估算方法。对于钨杂质,通过极紫外光谱（Extreme Ultraviolet Spectroscopy,EUV）诊断系统测量偏滤器区域钨杂质的辐射强度,再根据碰撞-辐射模型对该区域的钨杂质浓度进行了估算。对于Ne杂质,则通过等离子体有效电荷数(Z_eff)的变化进行了Ne杂质浓度估算。基于估算结果,对辐射偏滤器条件下的芯部杂质行为进行了讨论。上述杂质浓度评估方法对开展辐射偏滤器...     

欧洲联合环（JET）上的高密度、高性能高约束模等离子体

欧洲联合环上最近的实验[Rebut等人，《聚变工程与设计》22，7(1993)]目的是改善高密度的高约束模(H模)等离子体中的约束质量。通过强等离子体成形(三角形变度0．35＜δ＜0.5)、杂质植入和强场侧弹丸注入这三种方法已获得了如在密度接近或超过85％Grccnwald密度极限定标时由国际热核实验堆ITER—H98（7，2），定标预计的能量约束时间。观测到在约束末变差的情况下中心密度缓慢峰化。通过中心离子回旋共振加热可阻止锯齿损失和芯部杂质累积。在大三角形变度和杂质植入等离子体中，发现与Ⅰ型边缘定城模(ELMs)有关的平均功率损失的减小是因为在ELMs之间发生了附加损失。观炽到宽带磁起伏，这使我们想起其它托卡马克上有小ELMs的情况。已改变等离子体位形以寻找边缘坪项参数和小ELM损失的最佳组合。     

诊断中性束在合肥托卡马克等离子体中的衰减计算

考虑诊断中性束在HT-7等离子体中的电离，复合和电荷交换，对不同靶等离子体的等离子体温度、密度和杂质含量，计算了中性束在等离子体中的衰减。分析结果表明，等离子体的密度对中性束的衰减影响较大，而温度的变化对中性束衰减影响较小。当增大时，中性束衰减率随等离子体密度显著增大；当中性束的能量增大时，中性束也衰减较甚。含杂质中性束的衰减率也增大。最后，根据诊断中性束在EAST托卡马克中等离子体衰减的计算结果，给出了EAST托卡马克中等离子体所要求的诊断中性束参数。     

Tomography of emissivity for Doppler coherence imaging spectroscopy diagnostic in HL-2A

A newly developed Doppler coherence imaging spectroscopy(CIS) technique has been implemented in the HL-2 A tokamak for carbon impurity emissivity and flow measurement. In CIS diagnostics, the emissivity and flow profiles inside the plasma are measured by a camera from the line-integrated emissivity and line-averaged flow, respectively. A standard inference method, called tomographic inversion, is necessary. Such an inversion is relatively challenging due to the ill-conditioned nature. In this article, we report the recent application and comparison of two different tomography algorithms, Gaussian process tomography and Tikhonov tomography, on light intensity measured by CIS, including feasibility and benchmark studies.Finally, the tomographic results for real measurement data in HL-2A are presented.     

Investigation on impurity transport using LBO technique

1. IntroductionIt is a common phenomenon in the tokamak devices that impurities have a concentrated trend towards the plasma central region. Impurity sourcesand its transport are very complicated, traditionalpassive methods can not be satisfied for the investigation of impurity transport. So transient perturbation methods have been developed and recognizedas the most appropriate for impurity transport measurement.The LBO technique is just the right transient perturbation method for this task…     

Observation of Impurity Accumulation After Hydrogen Multi-Pellet Injection in Large Helical Device

Impurity accumulation is studied for neutral beam-heated discharges after hydrogen multi-pellet injection in Large Helical Device (LHD). Iron density profiles are derived from radial profiles of EUV line emissions of FeXV-XXIV with the help of the collisional-radiative model. A peaked density profile of Fe²³⁺ is simulated by using one-dimensional impurity transport code. The result indicates a large inward velocity of -6 m/s at the impurity accumulation phase. However, the discharge is not entirely affected by the impurity accumulation, since the concentration of iron impurity, estimated to be 3.3x10^-5 to the electron density, is considerably small. On the other hand, a flat profile is observed for the carbon density of C⁶⁺, which is derived from the Z_eff profile, indicating a small inward velocity of -1 m/s. These results suggest atomic number dependence in the impurity accumulation of LHD, which is similar to the tokamak result.     

DIVIMP Modeling of Impurity Transport in EAST

Simulations of carbon impurity transport in SOL/divertor plasmas with Ohmic heating on EAST tokamak were performed using the two-dimensional（2D）Monte Carlo impurity transport code DIVIMP.The background plasmas for DIVIMP simulations were externally taken from B2.5/Eirene calculation.Besides the basic output of DIVIMP,the 2D density distributions of the carbon impurity with different ionization states and neutral carbon atoms were obtained,the2D distributions of CII and CIII emissivities from C＋1and C＋2radiation respectively were also calculated.Comparison between the measured and calculated CIII emissivities showed favorable agreement,indicating that the impurity physics transport models,as implemented in the DIVIMP code,are suitable for the EAST tokamak plasma condition.     

Numerical estimate of multi-species ion sound speed of Langmuir probe interpretations in the edge plasmas of Wendelstein 7-X

The recently modified EMC3-EIRENE code package has been widely applied as an edge-plasma analysis tool and resulted in successful validation against various measured trends seen in stellarator and tokamak plasma boundaries. It has been shown that the code package applied for Wendelstein 7-X(W7-X) discharges in the interpretive mode can assess the impact of impurity effects on the electron density, measured by a set of Langmuir probes. In particular the spatial quantification of impurities and effects from the effective charge state Zeffand effective mass meff, which are non-trivial to record by diagnostics, were examined. The results showed that earlier assumptions of the effective charge-state distribution and effective mass for reported Langmuir probe measurements must be revised. Subsequently, reprocessing these measurements with code-interpreted spatial profiles of the effective charge state and effective mass led to an overall improved physical consistency.     

Study on Radial Position of Impurity Ions in Core and Edge Plasma of LHD Using Space-Resolved EUV Spectrometer

Radial profiles of impurity ions of carbon, neon and iron were measured for high-temperature plasmas in large helical device (LHD) using a space-resolved extreme ultraviolet (EUV) spectrometer in the wavelength range of 60 to 400?. The radial positions of the impurity ions obtained are compared with the local ionization energies, Ei of these impurity ions and the electron temperatures TeZ there. The impurity ions with 0.3?Ei?1.0 keV are always located in outer region of plasma, i.e., 0.7?ρ?1.0, and those with Ei?0.3keV are located in the ergodic layer, i.e., 1.0?ρ?1.1, with a sharp peak edge., where ρ is the normalized radial position. It is newly found that TeZ is approximately equal to Ei for the impurity ions with Ei?0.3keV, whereas roughly half the value of Ei for the impurity ions with 0.3?Ei?1.0keV. It is known that TeZ is considerably lower than Ei in the plasma edge and approaches to Ei in the plasma core. Therefore, this result seems to originate from the difference in the transverse transport between the plasma edge at ρ?1.0 and the ergodic layer at ρ?1.0. The transverse transport is studied with an impurity transport simulation code. The result revealed that the difference appearing in the impurity radial positions can be qualitatively explained by the different values of diffusion coefficient, e.g., D=0.2 and 1.0m2/s, which can be taken as a typical index of the transverse transport.     

Development of vacuum ultraviolet spectroscopy for measuring edge impurity emission in the EAST tokamak

The dominant wavelength range of edge impurity emissions moves from the visible range to the vacuum ultraviolet(VUV) range, as heating power increasing in the Experimental Advanced Superconducting Tokamak(EAST). The measurement provided by the existing visible spectroscopies in EAST is not sufficient for impurity transport studies for high-parameters plasmas. Therefore, in this study, a VUV spectroscopy is newly developed to measure edge impurity emissions in EAST. One Seya-Namioka VUV spectrometer(McPherson 234/302) is used in the system, equipped with a concave-corrected holographic grating with groove density of 600 grooves mm~(–1). Impurity line emissions can be observed in the wavelength range ofλ=50–700 nm, covering VUV, near ultraviolet and visible ranges. The observed vertical range is Z=-350–350 mm. The minimum sampling time can be set to 5 ms under full vertical binning(FVB) mode. VUV spectroscopy has been used to measure the edge impurity emission for the 2019 EAST experimental campaign. Impurity spectra are identified for several impurity species, i.e., lithium(Li), carbon(C), oxygen(O), and iron(Fe). Several candidates for tungsten(W) lines are also measured but their clear identification is very difficult due to a strong overlap with Fe lines. Time evolutions of impurity carbon emissions of CII at 134.5 nm and CIII at97.7 nm are analyzed to prove the system capability of time-resolved measurement. The measurements of the VUV spectroscopy are very helpful for edge impurity transport study in the high-parameters plasma in EAST.     

Temporal and spatial study of differently charged ions emitted by ns-laser-produced tungsten plasmas using time-of-flight mass spectroscopy

Tungsten (W) is an important material in tokamak walls and divertors.The W ion charge state distribution and the dynamic behavior of ions play important roles in the investigation of plasma-wall interactions using laser-ablation-based diagnostics such as laser-induced breakdown spectroscopy and laser-induced ablation spectroscopy.In this work,we investigate the temporal and spatial evolutions of differently charged ions in a nanosecond-laser-produced W plasma in vacuum using time-of-flight mass spectroscopy.Ions with different charge states from 1 to 7 (W+ to W7+) are all observed.The temporal evolutions of the differently charged ions show that ions with higher charge states have higher velocities,indicating that space separation occurs between the differently charged ion groups.Spatially-resolved mass spectroscopy measurements further demonstrate the separation phenomenon.The temporal profile can be accurately fitted by a shifted Maxwell-Boltzmann distribution,and the velocities of the differently charged ions are also obtained from the fittings.It is found that the ion velocities increase continuously from the measured position of 0.75 cm to 2.25 cm away from the target surface,which indicates that the acceleration process lasts through the period of plasma expansion.The acceleration and space separation of the differently charged ions confirm that there is a dynamic plasma sheath in the laser-produced plasma,which provides essential information for the theoretical laser-ablation model with plasma formation and expansion.     

A Study of the von Neumann Stability Analysis of a Semi-implicit Numerical Method Applied Over the Radial Impurity Transport Equation in Tokamak Plasma

The radial impurity transport equation for tokamak plasma is a form of diffusion–convection–reaction equation. The impurity transport equation is solved to determine the distribution of impurity (non-fuel) ion species with different ionization states perpendicular to magnetic surfaces of tokamak plasma. The equation for each charge (ionization) state Z is a non-linear, second-order in space, first-order in time, parabolic partial differential equation coupled to the previous Z???1 and the next Z?+?1 charge states of the impurity species through its reaction term. The number of differential equations to be solved simultaneously is hence determined by the number of ionization states of the impurity species studied. The solution to the set of these coupled equations can be obtained using a semi-implicit numerical method applied on it. The present study describes the application of von Neumann stability analysis over the semi-implicit numerical method applied over the radial impurity transport equation and determines a generic stability criterion for the method. The stability analysis is further illustrated using the geometry of Aditya tokamak installed at the Institute for Plasma Research Gandhinagar, India as an example. The impurity species considered is oxygen (Atomic number?=?8). This leads to a set of eight coupled equations for charge states Z?=?1 to 8 over which von Neumann analysis is illustrated in present study.     

Impurity Measurement and Study on HL-2A Divertor Tokamak

HL-2A tokamak with two close divertors has been operated since 2003. In the experimental campaign of 2004 the divertor configuration has been successfully formed and the sillconization as a wall conditioning has been firstly done in this device. The divertor configuration can be reconstructed by the CFc code. Impurity behavior has been investigated during the experiment with divertor configuration and wall conditioning. The reduction of impurity is clear under both conditions of divertor configuration and siliconization.