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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] 相似文献
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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。 相似文献
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在HL-2A装置上研制了用于测量等离子体密度分布的两套幅度调制微波反射仪。微波反射仪采用时间延迟法。这两套微波反射仪有不同的频率范围(26.5～40GHz和40～60GHz),它们所对应的密度测量范围是(0.84～1.98)×1019m-3和(1.98～4.47)×1019m-3。时间分辨率可达1ms,空间分辨率约为5mm。 相似文献
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田文静;杨宗谕;许敏;龙婷;何小雪;柯锐;杨硕苏;余德良;石中兵;高喆 《物理学报》2025,(7):345-354
对于旨在实现高参数和长脉冲运行的磁约束聚变装置而言,基于离子温度实时测量的等离子体反馈控制至关重要,而电荷交换复合光谱是等离子体离子温度的基本测量手段.本文提出了一种基于神经网络的电荷交换复合光谱诊断数据快速分析方法,并对其跨参数区间的外推能力进行研究.该研究使用中国环流器二号A装置HL-2A的12.2×10～4个光谱数据及离线解谱获得的离子温度标签值构成数据集.模型基于卷积神经网络,相对于标签值实现了拟合优度R2～0.92的效果,在推理阶段单光谱耗时小于1 ms,相比传统方法加速了100—1000倍.在外推能力方面,提出基于低温度实验数据生成高温度的合成光谱数据的方法,并通过在只包含离子温度2 keV以下的训练集中添加大约5%的合成数据,大幅增加了模型在外推参数区间(2—4 keV)分析的准确性,将模型在3—4 keV区间测试的误差降低了约60%.该研究证明了在磁约束核聚变领域利用合成数据提升人工智能算法性能的可行性. 相似文献
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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. 相似文献
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崔正英 徐媛 冯北滨 许宇鸿 丁玄同 季小全 李永高 石中兵 钟武律 蒋敏 宋绍栋 程均 高金明 曹建勇 董春凤 张凯 陈程远 黄梅 杨青巍 段旭如 《中国物理 B》2017,26(8):85205-085205
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. 相似文献
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龚少博;张通川;郭文平;侯智培;翟文延;刘春华;邓必河;石中兵;钟武律;许敏;段旭如 《核聚变与等离子体物理》2025,45(1):64-68
HL-3装置上发展了一套垂直边缘汤姆逊散射诊断系统;该系统采用波长1064nm、能量0.6~2J、重复频率30Hz、脉冲宽度15ns的Nd:YAG激光作为诊断光束。入射激光垂直穿过等离子体区域;在水平方向上收集散射光信号。对Nd:YAG激光传播特性进行了实验研究;利用非理想高斯光束传播方程对实验数据进行了拟合;得到了入射激光的束腰半径、束腰位置及品质因子等重要参数。基于实验获得的入射激光参数;设计了一套伽利略扩束准直系统和单透镜聚焦方案;在观测视场中心成功获得了束腰半径为2mm的激光光斑。所开展的Nd:YAG激光传播特性研究不仅是确定汤姆逊散射系统观测视场的关键;也是开展消杂散光孔径光阑设计的基础。 相似文献
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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。 相似文献
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