Analysis of Azimuthal Doppler Shift of Anisotropically Absorbed Laguerre-Gaussian Beam Propagating in Transverse Flow
Analysis of Azimuthal Doppler Shift of Anisotropically Absorbed Laguerre-Gaussian Beam Propagating in Transverse Flow
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DOI：
10.1585/pfr.17.1401099
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发表时间：
2022-09-14
影响因子：
0.8
通讯作者：
Aramaki, Mitsutoshi
中科院分区：
文献类型：
--
作者：
Minagawa, Hiroki;Yoshimura, Shinji;Aramaki, Mitsutoshi
在研究等离子体与物质相互作用过程中，物质上的粒子通量是一个重要参数。利用常规多普勒光谱学，难以测量垂直于材料的流速，因为只能测量投影在波数矢量上的速度分量。为了克服这个限制，我们正在开发一种横向流动测量方法，使用拉盖尔-高斯（LG）光束吸收光谱的方位多普勒频移。在本文中，这种光谱方法的可行性已被检查的数值分析。由于方位多普勒频移，LG光束在横向流中被各向异性吸收。由于各向异性的LG光束随着传播而旋转，因此在LG光束吸收光谱中，等离子体中共振吸收的空间结构和已经传播通过等离子体的LG光束的强度结构不可避免地不同。结果表明，在LG光束强度分布达到最大值的位置，方位多普勒频移的偏差减小到几个百分点。因此，可以通过适当地选择用于评估方位多普勒频移的波束横截面上的位置来以足够的精度测量横向流。(C)2022日本等离子体科学与核聚变研究学会
The particle flux onto a material is an important parameter in the study of the plasma-material interaction. With conventional Doppler spectroscopy, it is difficult to measure the flow velocity perpendicular to the material because only the velocity component projected on the wave number vector can be measured. To overcome the limitation, we are developing a transverse flow measurement method using the azimuthal Doppler shift of a Laguerre-Gaussian (LG) beam absorption spectroscopy. In this paper, the feasibility of this spectroscopy method has been examined by numerical analysis. The LG beam is anisotropically absorbed in the transverse flow due to the azimuthal Doppler shift. Since the anisotropic LG beam rotates with propagation, the spatial structure of resonance absorption in plasma and the intensity structure of the LG beam that has propagated through the plasma are inevitably different in the LG beam absorption spectroscopy. It was shown that the deviation from the original azimuthal Doppler shift is reduced to several percent at the position where the intensity distribution of the LG beam reaches its maximum value. Therefore, the transverse flow can be measured with sufficient accuracy by properly selecting the position on the beam cross-section used to evaluate the azimuthal Doppler shift.(C) 2022 The Japan Society of Plasma Science and Nuclear Fusion Research