Behaviors of Electron Heat Transportation in HT-7 Sawtoothing Plasma

It is found that in HT-7 ohmic plasma, main energy loss comes from electron heat conduction, hence quantitative data of electron heat diffusivity is a very important issue for investigation of electron heat transportation behavior in different target plasmas so as to get high performance plasma. A time-to-peak method of the heat pulse propagation originating from the sawtooth activity on the soft x-ray intensity signal has been adopted to experimentally determine electron heat diffusivity χe^HP on the HT-7 tokamak. Aiming to improve the signal-to-noise (S/N) ratio of the original signal to get a stable and reasonable electron heat diffusivity χe^HD value, some data processing methods, including average of tens of sawteeth, is discussed. The electron heat diffusivity χe^HP is larger than χe^PB which is determined from the balance of background plasma power. Based on variation of the measured electron heat diffusivity χe^HP , performances of different high confinement plasmas are analyzed.     

软X射线谱学显微图像漂移的精确校正

上海光源软X射线谱学显微实验站(BL08U)新建成并投入使用,已实现30nm空间分辨的元素成像功能。由于机械精度和重复精度误差,不同能量扫描出的两幅或多幅图像位置会有一定量的漂移。在高分辨情况下图像漂移不仅给数据处理带来严重误差,导致分辨率下降,甚至产生错误,所以需对不同能量下的图像配准。硬件上用激光干涉仪对样品定位,并通过slope函数确定样品台移动的漂移规律,从而在移动样品过程中对位置动态校正。软件上发展一种新的基于图像分窗口相关性的数字图像自动配准方法,对采集到的两幅或多幅STXM图像配准,对每一子区的自动相关匹配来对整幅图像精确配准,在x和y方向配准精度可达小于1像素尺度(STXM目前的要求)。     

光栅单色器系统超环面镜转动机构优化设计

为了减少软X射线谱学显微光束线开光后光栅单色器系统光通量漂移的稳定时间,通过有限元分析开光后超环面镜转动机构的瞬态温度,得到2 h后推杆方向总的线性热膨胀量,以及由此引起聚焦光斑在出射狭缝中心处的水平偏移量。结果显示:超环面镜推杆方向热膨胀量为0.97μm,聚焦光斑的水平偏移量达到141μm,而狭缝水平开口仅为50μm,由此推断光通量漂移产生的主要原因是超环面镜吸收的热负载缓慢传导至正弦机构引起Pitch角持续变化。据此设计了超环面镜间接水冷结构,通过对结构优化后的超环面镜箱开光测试,将稳定时间由2 h以上缩短到30 min左右,有效地提升了用户机时的利用效率。     

The Electron Temperature Estimation Using Soft X-Ray Imaging in HT-7 Tokamak

In order to estimate the electron temperature soft x-ray imaging diagnostics using a double filter technique has been developed in the HT-7 tokamak. The chosen thicknesses of the Be foil are 12.5 μm and 70 μm, respectively. In this article both the main design of the diagnostic configuration and the method to estimate the electron temperature are presented. The results agree with those estimated from the soft x-ray pulse height analyzer （PHA）. The main causes of systematic error have also been investigated.