CFQS装置准环对称测试用磁体电源系统设计

CFQS装置是中国西南交通大学(SWJTU)和日本国家核融合科学研究所(NIFS)联合设计制造的中国首台准环对称仿星器,为满足装置0.1 T稳态运行的实验要求,需要为其磁体线圈设计相应的电源系统。本设计方案考虑工程实际估算线路阻抗,考虑工程裕度、电源以负载参数的1.2倍进行计算,并建立电源系统的Simulink仿真模型,分析负载电流纹波大小及网侧谐波含量。根据仿真结果优化设计方案,通过在直流侧增加无源滤波器,减小输出电流纹波,分析直流侧电压代数形式,计算滤波器参数,并仿真调节得到更加符合实际需求的滤波器参数,满足装置准环对称位形的分布磁场精度对磁体线圈电流纹波的要求。     

HT-7超导托卡马克边界等离子体参量及其涨落的实验研究

利用径向可移动朗缪尔三探针和马赫探针对HT-7超导托卡马克边界等离子体参量及其涨落进行了空时空分辨测量.给出了欧姆放电及其与低杂波电流驱动共同作用下边界等离子体电位φ_p、电子温度T_e和电子密度n_e及其涨落的径向分布.实验表明,在限制器附近,存在一由E_r×B确定的极向旋转速度剪切层.在剪切层内,T_e和n_e分布较陡,且φ_p,T_e和n_e的相对涨落水平下降明显.这说明剪切层对边界区的等离子体涨落具有抑制作用.低杂波驱动使径向电场梯度变陡,从而使剪切程度加深但对剪切层宽度无影响.此外,测量表明等离子体环向速度马赫数M_φ存在径向梯度.环向流的这种径向梯度可能是形成径向电场所需的平均极向流的一种重要驱动源 关键词： 托卡马克 边界涨落 低杂波驱动     

HT-7超导托卡马克边缘涨落谱特征及湍流输运研究

用郎缪尔三探针对HT-7超导托卡马克边缘等离子体涨落进行了高时空分辩测量.给出了欧姆放电下涨落幅度的径向分布、谱特征及传播特性.实验观察表明,在由E_r×B确定的极向旋转速度剪切层附近,等离子体电位、电子温度和电子密度的相对涨落水平和两两间的相干系数均有明显下降,其极向互相关函数亦减小,这说明剪切层对涨落具有去相关作用.由涨落驱动的径向局域粒子输运通量Γ_tur测量显示出湍动输运具有时间上的阵发特性。将悬浮电位涨落φ_f2的自动率谱P_{( 关键词： 托卡马克 边界涨落 湍流输运}     

EXPERIMENTAL EVIDENCE OF THE SELF-SIMILARITY AND LONG-RANGE CORRELATIONS OF THE EDGE FLUCTUATIONS IN HT-6M TOKAMAK

To better understand long-time-scale transport dynamics, the rescaled range analysis techniques, the autocorrelation function (ACF) and the probability distribution function (PDF) are used to investigate long-range dependences in edge plasma fluctuations in HT-6M tokamak. The results reveal the self-similar characters of the electrostatic fluctuations with self-similarity parameters (Hurst exponent) ranging from 0.64 to 0.79, taking into consideration the {\vec E}_r×{\vec B} rotation-sheared effect. Fluctuation ACFs of both the ion saturation current and the floating potential, as well as PDF of the turbulence-induced particle flux, have two distinct time scales. One corresponds to the decorrelation time scale of local fluctuations (μs) and the other lasts to the order of the confinement time (ms). All these experimental results suggest that some of the mechanisms of the underlying turbulence are consistent with plasma transport as characterized by self-organized criticality(SOC).     

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.