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在HL-2A装置孔栏位形放电的等离子体实验中,电子回旋辅助加热期间观察到了等离子体约束改善的现象,并对等离子体从低约束模式(L模)向约束改善模式转换时的等离子体线平均电子密度、等离子体储能、分界面内辐射功率、能量约束时间、Hα辐射等进行了研究。同时,分析了电子密度和等离子体辐射功率的空间分布随时间的演化。对改善约束的相关功率(辅助加热、欧姆加热功率和损失功率)进行了分析,并研究了等离子体约束改善转换时的边界净输入功率(阈值)与电子线平均密度和环向磁场的关系。     

Properties of plasma radiation during discharges with improved confinement on HL-2A Tokamak

In the recent experiment on the HL-2A tokamak,two types of improved confinement regimes have been achieved in different configurations.One is the improved confinement regime in limiter configuration during electron cyclotron resonant heating (ECRH),characterized by a sharp decrease in H α emission accompanied by an increase in the total radiation of plasma,the line averaged electron density and the stored energy of plasma.The other is high confinement regime (H-mode) in divertor configuration during a combination of ECRH and Neutral beam injection (NBI) heating,characterized with edge localized modes (ELMs) besides the features mentioned above.The ELMs are found to be localized on the plasma edge (r/a ≥ 0.8),causing average losses of particles and stored energy in the ranges of about 1-3% and 3-5% respectively during a single ELM event.So far,the ELMs observed in the HL-2A are type III ELMs with low amplitude and high repetition frequency in a range from 200 Hz to 350 Hz.An investigation of the radiated power density profiles shows that radiative cooling effect plays a significant role in the transition back to the L-mode and the triggering of ELM events.     

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.     

用软X射线成像观察HL-2A装置中的杂质注入过程

激光吹气是主动性研究等离子体内部杂质输运的最佳方法之一。杂质的注入用杂质粒子流表示 Г=-DVn＋Lvn 式中，D为输运系数，V为对流速度。激光吹气实验可在放电中选择不同时段注入可控量的杂质。由于杂质注入量很小且附加脉冲信号持续时间很短，等离子体电流和温度都没有明显扰动。杂质约束时间可根据中心道信号衰减时间来计算。     

Study of runaway electron behaviour during electron cyclotron resonance heating in the HL-2A Tokamak

During the current flat-top phase of electron cyclotron resonance heating discharges in the HL-2A Tokamak, the behaviour of runaway electrons has been studied by means of hard x-ray detectors and neutron diagnostics. During electron cyclotron resonance heating, it can be found that both hard x-ray radiation intensity and neutron emission flux fall rapidly to a very low level, which suggests that runaway electrons have been suppressed by electron cyclotron resonance heating. From the set of discharges studied in the present experiments, it has also been observed that the efficiency of runaway suppression by electron cyclotron resonance heating was apparently affected by two factors: electron cyclotron resonance heating power and duration. These results have been analysed by using a test particle model. The decrease of the toroidal electric field due to electron cyclotron resonance heating results in a rapid fall in the runaway electron energy that may lead to a suppression of runaway electrons. During electron cyclotron resonance heating with different powers and durations, the runaway electrons will experience different slowing down processes. These different decay processes are the major cause for influencing the efficiency of runaway suppression. This result is related to the safe operation of the Tokamak and may bring an effective control of runaway electrons.     

Density Fluctuation Measurements Using FIR Interferometer on HL-2A Tokamak

Density fluctuations were first measured in the core region of HL-2A tokamak plasma using a newly developed multi-channel FIR interferometer system. In divertor ohmic discharges, we measured the radial density fluctuation levels of 5%, which increase to 10-20% during the appearance of MHD activity. Most of the power density in the density fluctuation spectrum is directly associated with m = 2 tearing modes. The fluctuation levels reduce to 1/3 and plasma confinement is improved during off-axis electron-cyclotron-resonance heating （ECRH）.     

Observation of Fishbone-Like Instabilities Excited by Energetic Electrons on the HL-2A Tokamak

Strong burst of an internal kink mode is observed on the HL-2A tokamak. Features of the fishbone-like mode are presented. The fishbone-like instabihties can be driven during electron cyclotron resonance heating （ECRH） and can be excited on the high field side （HFS） by ECRH. It is found for the first time that the modes also present themselves on the low field side （LFS） during ECRH. Experiments show that the energetic electrons with energy of 35-70 keV play a dominant role in the excitation mechanism, and the experimental results are also consistent with our calculation ones.     

HL—1M装置等离子体软X射线的锯齿和模行为

用高灵敏、高时空分辨的软Ｘ射线诊断系统，诊断ＨＬ－１Ｍ装置中等离子体的锯齿振荡。对观测到的四种主要锯齿作了介绍，对出现最多的有模经典锯齿和有模非经典锯齿作了详细描述和分析。结果表明，后者（主要在低ｑａ放电中出现）具有比前者低的中心ｑ（０）值，在物理机制上与前者不同，属湍流模型范畴。     

共聚结构和分子量对热塑性聚酰亚胺树脂熔融与耐热性能的影响

基于具有刚性主链结构的4,4'-(六氟亚异丙基)双邻苯二甲酸酐/对苯二胺(6FDA/p-PDA)树脂体系, 通过共聚引入间苯二胺(m-PDA)、 4,4'-二氨基-2,2'-双三氟甲基联苯(TFDB)和9,9'-双(4-氨基苯基)芴(BAFL)等主链刚性且兼具大自由体积特性的芳香二胺, 以非反应性封端剂邻苯二甲酸酐(PA)对分子量进行调控, 设计制备了系列分子量可控的热塑性聚酰亚胺(TPI)树脂. 系统研究了共聚结构和分子量对TPI树脂熔融性能和耐热性能的影响, 构建了聚合物的聚集态结构与树脂熔融性能的对应关系, 并对树脂的室温和高温力学性能进行了评价. 研究结果表明, 大自由体积的芳香二胺共聚结构的引入可有效降低分子链堆砌密度, 增大聚合物的自由体积, 从而赋予树脂良好的熔融性能. 降低设计分子量可进一步改善树脂的熔融加工性. 这类具有刚性主链结构的TPI树脂兼具优异的耐热性能和力学性能, 树脂的玻璃化转变温度在308~338 ℃之间, 以TFDB和BAFL共聚制备的TPI-C-25K和TPI-D-25K树脂表现出高强高韧的特性, 拉伸和弯曲强度分别超过120 MPa和190 MPa, 断裂伸长率大于8.2%, 并且在250 ℃高温下表现出良好的耐热稳定性.     

椭圆截面的Abel逆变换方法

介绍了等离子体椭圆截面的Abel逆变换方法,并和圆截面的Abel逆变换方法进行了比较。给定一个探测阵列对一个辐射源函数的测量结果,分别用Barr方法、等值同心圆方法和幂级数方法进行了椭圆逆变换,结果表明该方法的可靠性可应用于实验数据处理中。