HL-2A装置快离子Dα诊断和模拟分析

介绍了HL-2A装置上的快离子Dα(FIDA)诊断,并利用FIDASIM与TRANSP程序对快离子进行模拟分析,通过分析FIDA谱获得了快离子在相空间的分布。对模拟结果与实验结果进行对比,分析表明模拟得到的FIDA谱的演化趋势与实验吻合,验证了用TRANSP程序模拟的快离子分布的可靠性。     

Preliminary analysis of impurity transport in HL-2A ohmic discharges

This paper describes the behaviour of impurity transport in HL-2A ohmic discharges. In 2005, small quantities of metallic impurities （A1, Ni and Ti） were successfully injected into HL-2A plasmas by laser blow-off technique, and their progression was followed by the soft x-ray cameras with good spatial and temporal resolutions. The impurity confinement time is estimated from the characteristic decay time of the soft x-ray signal of the injected impurities, and it is about 30-60 ms. The transport coefficients of impurities （including diffusion coefficient and convection velocity） in radial different region have been derived by using a one-dimenslonal impurity transport code, the results present that diffusion coefficient is much smaller in the central region of plasmas than the outside of it, and it is much larger than that of neoclassical theory predictions; namely, it is anomalous.[第一段]     

Pellet Enhanced Performance on the HL-2A Tokamak

Enhanced confinement has been achieved by the centre fuelling of pellet injection on the HL-2A tokamak. The energy confinement time increases from 50ms to 140ms after the pellet injection. Experimental results show that the improvement of the confinement is related to the decrease of the electron heat transport. Several phenomena which may lead to the improved confinement have been observed in the experiments. After the pellet injection the hollow electron temperature profile and the peaked electron density profile can be sustained for about 200ms, but the improved confinement remains at about 500ms. Sawtooth features and MHD modes have been observed by soft x-ray array and the Mirnov probes. The weak （or reversed） magnetic shear is thought to be an important cause of the low electron heat transport.     

HL-2A装置高密度破裂的实验观测

大破裂发生时，不仅会在第一壁和偏滤器靶板上产生大的热负载沉积。并会由于晕电流而产生强烈电磁力。这种电磁力能够对偏滤器室及真空室内的部件造成损害。因此，如何避免大破裂放电是托卡马克运行中一个重要课题。为了减轻和控制大破裂，必须清楚地认识其产生机制和发生特性。     

HL-2A装置偏滤器中的微波干涉仪测量

微波干涉仪测量等离子体电子密度是一种常规监测工具，利用这种工具可以给出电子密度随时间变化的波形图。等离子体电子密度和微波干涉仪测出的相位差之间的关系为：     

基于谱估计方法的等离子体湍流三波耦合数据处理算法

基于数字谱分析技术求解波耦合方程,进而计算与三波相互作用相关联的线性耦合系数和能量转移,以此开发了数据处理程序用于研究HL-2A 装置等离子体边缘湍流中的非线性能量传递过程。介绍了算法设计和开发的主要思想。应用该程序对与带状流相关的一次放电的实验数据进行了数据处理研究。结果表明,带状流是由等离子体湍流的能量逆级联所驱动的。     

微波多普勒反射计数据分析的一种优化方法

结合对多普勒频谱的分析,提出一种基于双高斯拟合的轴对称-非对称谱(SAS)分析方法。在此方法下,功率谱主要由轴对称功率谱和非轴对称功率谱两部分组成。前者主要由等离子体截止层密度的扰动调制决定,后者主要由波数为k _⊥=2k₀sinθ 的湍流的极向密度扰动决定。在分析多普勒反射计的数据时,相较于常用的频谱重心(COG)分析方法和相位微分(δ-phase)法,SAS 谱分析不仅提高了求取多普勒频移的准确性,同时还可以获取等离子体中波数为k_⊥ 的极向湍流的密度扰动强度和截止层的密度扰动强度。     

HL-2A 装置上的快扫Q 波段微波反射系统研制

介绍了在HL-2A 装置上发展的一套快速扫频的Q 波段外差微波反射系统,用于高时空分辨测量等离子体边缘到约束区的电子密度分布。该系统采用外差式连续波扫频调制技术(VCO),由外部任意波电压控制,工作频率为33~50GHz,全波段扫频周期达到6μs。在台面标定中发展了VCO 源的动态标定技术,并解决了微波源及器件的非线性响应、波导的色散特性等因素造成差频频率动态范围过大的问题,使反射面固定时系统输出的差频为定频信号,有利于降低噪声干扰和数据处理。同时发展了直接相位处理技术,实现快速的电子密度分布反演。实验中用该微波反射系统测得了L 模、H 模等不同等离子体放电条件下的电子密度分布,观测ELM 爆发前后台基区的形成与垮塌过程。     

Favourable scenarios established by SMBI for the realization of the ELMy H-mode at HL-2A

The ELMy H-mode plasmas realized with the supersonic molecular beam injection(SMBI) are studied in relation to the energy confinement and the heating power for the L–H transition(P_(L-H) ) in the HL-2A tokamak. A database is assembled for this study based on the ELMy H-mode discharges during the experimental campaigns in the period 2009–2013at the HL-2A tokamak. The statistical results show that the SMBI is favourable for reaching the H-mode by reducing the heating power at the L–H transition and for the H-mode performance by improving the energy confinement compared with the ordinary gas puffing(GP). The reduction of P_(L-H) is about 20% when the density is low, and the energy confinement enhancement factor of H_(H98y2)= τ_E/τ_(th,98y2) ≈ 1.5 is achieved with the SMBI. Note that in the database the density dependence of P_(L-H) is non-monotonic with the ˉne,min≈ 3×10~(19) m~(-3) at which the P_(L-H) is minimum. Most of P_(L-H) data are on the low density branch where the P_(L-H) increases with the decrease in density. The minimum of the P_(L-H) in HL-2A is comparable to the ITPA multi-machine threshold power scaling P_(thr■scal08). The physics behind the reduction of the P_(L-H) with the SMBI is also investigated in relation to the change of the density gradient at the plasma edge, the gas fuelling efficiency, and the recycling.     

A nonlinear wave coupling algorithm and its programing and application in plasma turbulences

The fully developed turbulence can be regarded as a nonlinear system, with wave coupling inside, which causes the nonlinear energy to transfer, and drives the turbulence to develop further or be suppressed. Spectral analysis is one of the most effective methods to study turbulence system. In order to apply it to the study of the nonlinear wave coupling process of edge plasma turbulence, an efficient algorithm based on spectral analysis technology is proposed to solve the nonlinear wave coupling equation. The algorithm is based on a mandatory temporal static condition with the nonideal spectra separated from the ideal spectra. The realization idea and programing flow are given. According to the characteristics of plasma turbulence, the simulation data are constructed and used to verify the algorithm and its implementation program. The simulation results and experimental results show the accuracy of the algorithm and the corresponding program, which can play a great role in the studying the energy transfer in edge plasma turbulences. As an application, the energy cascade analysis of typical edge plasma turbulence is carried out by using the results of a case calculation. Consequently, a physical picture of the energy transfer in a kind of fully developed turbulence is constructed, which confirms that the energy transfer in this turbulent system develops from lower-frequency region to higher-frequency region and from linear growing wave to damping wave.