扫描透射离子显微成像系统的建立和实验研究

Scanning transmission ion microscopy in Shanghai scanning proton microprobe system

基于上海应用物理研究所的扫描质子微探针系统,对扫描透射离子显微成像(STIM)技术进行了仿真分析和实验研究,建立了基于中值滤波方法的数据处理程序,获得了大鼠股骨切片的面密度分布和薄壁小球的离轴STIM图像。理论分析和实验结果显示:由在轴探测数据的中值滤波结果可以计算出定量的面密度分布信息,由能量窗滤波的离轴探测数据则可以给出高分辨的定性图像,这在薄样品、强束流、以及质子激发X荧光(PIXE)分析同时进行的STIM分析中尤为有用;增加获取的事件数、选择合适的滤波方法可以使测量误差远小于阻止本领计算带来的误差。该方法可以用于测量几十μm尺度样品的绝对质量以及辅助PIXE技术进行元素定量分布分析。

Based on the scanning proton microprobe system in Shanghai Institute of Applied Physics, scanning transmission ion microscopy（STIM） experimentation were carried out and simulated by SIMNRA procedure. A paraffin-embedded slice of rat＇s thighbone and a thin small ball were tested by on-axis and off-axis STIM respectively. P_STIM software dedicated to STIM analysis of thin samples using proton beams was developed, which includes the reconstruction of the median filtering energy loss image of the sample, as well as accurate calculation of sample thickness of the scanning regions. Theoretical analysis and experimental results showed that median filtering used to reduce the data acquired by on-axis detection provides quantitative areal density distribution results and energy-window filtering method used for handling off-axis detection data offers the qualitative images; Off-axis detection coupled with energy-window filtering method is particularly useful in circumstances of thin samples, strong beam current, or STIM test accompanied by PIXE; For more events, selecting appropriate filtering method can reduce measurement errors effectively. Quantitative mass distribution of micrometer scale samples can be detected by this technique, and STIM results can be used for data normalization and self absorption correct in PIXE test.