Identification of m=2 competent mode of complex magneto-hydro-dynamics activities during internal soft disruption based on singular value decomposition and tomography of soft-X-ray emission on the HT-7 tokamak

In this paper,the singular value decomposition(SVD) method as a filter is applied before the tomographic inversion of soft-X-ray emission.Series of ’filtered’ signals including specific chronos and topos are obtained.(Here,chronos and topos are the decomposed spatial vectors and the decomposed temporal vectors,respectively).Given specific magnetic flux function with coupling m = 1 and m = 2 modes,the line-integrated soft-X-ray signals at all chords have been obtained.Then m = 1 and m = 2 modes have been identified by tomography of simulated ’filtered’ signals extracted by the SVD method.Finaly,using the experimental line-integrated soft-X-ray signals,m = 2 competent mode of complex magnetohydrodynamics(MHD) activities during internal soft disruption is observed.This result demonstrates that m = 2 mode plays an important role in internal disruption(Here,m is the poloidal mode number).     

间苯二酚在TiO2-石墨烯修饰玻碳电极上的电化学行为及测定

制备了TiO2-石墨烯修饰玻碳电极。用循环伏安法(CV)和差分脉冲伏安法(DPV)对间苯二酚在该修饰电极的电化学行为进行了研究。实验结果表明,在pH值为6.0的磷酸盐缓冲液(PBS)中,该修饰电极对间苯二酚具有良好的电催化作用。对TiO2-石墨烯用量、支持电解质、pH和扫描速度等实验条件进行了优化。在优化条件下,利用DPV测定,间苯二酚的氧化峰电流与其浓度在1.0×10-6～1.0×10-4mol/L范围内呈良好的线性关系,线性相关系数为0.995。检出限为2×10-7mol/L。将该方法应用于模拟水样中间苯二酚的测定,回收率为96.5～104.2%。     

HT-7托卡马克等离子体slide-away放电研究

在HT-7托卡马克上,只在等离子体放电击穿阶段充气,击穿后关闭充气阀门,让装置内真空室器壁的出气维持放电的进行,通过密度衰减实现了slide-away放电.实验分析了不同等离子体电流平台下的slide-away放电模式的密度阈值,以及相同充气量的条件下放电等离子体电流对实现slide-away放电的影响.研究了slide-away放电模式下密度提升对等离子体放电状态的影响.结果发现,slide-away放电模式下的密度提升使得H_a线辐射强度增强,等离子体中超热电子的约束性能变差,等离子体芯部的超热电子减少,高能逃逸电子厚靶轫致辐射增加. 关键词： slide-away放电 托卡马克 等离子体 逃逸电子     

二维硬X射线探测器自动标定平台研究

结合云台构建了EAST装置中二维硬X射线诊断的自动标定平台,通过调节云台的旋转和俯仰角度自动对探测器的所有像素点进行扫描测试,同时自动控制X射线管的束流能量和强度,从而对探测器每个像素点强度响应的线性度、不同像素点响应的一致性、相邻像素点之间的串扰等进行测量和标定。实验结果表明,探测器7×8像素点对硬X射线均有响应,强度响应的线性度可以达到R=0.999,初步验证了系统功能的可行性。     

AC operation and runaway electron behaviour in HT-7 tokamak

Operation of HT-7 tokamak in a multicycle alternating square wave plasma current regime is reported. A set of AC operation experiments, including LHW heating to enhance plasma ionization during the current transition and current sustainment, is described. The behaviour of runaway electrons is analysed by four HXR detectors tangentially viewing the plasma in the equatorial plane, within energy ranges 0.3--1.2~MeV and 0.3--7~MeV, separately. High energy runaway electrons (\sim MeV) are found to circulate predominantly in the opposite direction to the plasma current, while the number of low energy runaway electrons (\sim tens to hundreds of keV) circulating along the plasma current is comparable to that in the direction opposite to the plasma current. AC operation with lower hybrid current drive (LHCD) is observed to have an additional benefit of suppressing the runaway electrons if the drop of the loop voltage is large enough.     

Repetitive ＇Snakes＇ and Their Damping Effect on Core Toroidal Rotation in EAST Plasmas with Multiple H-L-H Transitions

Repetitive impurity snake modes are observed after H-L mode transitions （high to low confinement modes） in EAST plasmas exhibiting multiple H-L-H transitions. Such snake modes are observed to lower the core plasma toroidal rotation. A critical impurity strength factor associated with snake-mode formation is estimated to be as high as αz,c = nz,cZ^2/ne - 0.75. These observations have implications for ITER H-mode sustainability when the heating power is only slightly above the H-mode power threshold.