Diffuse reflection model and noise stabilization for tangential image tomographic reconstruction (TITR) code
Diffuse reflection model and noise stabilization for tangential image tomographic reconstruction (TITR) code
复制标题
用于切向图像断层重建 (TITR) 代码的漫反射模型和噪声稳定
DOI：
10.1088/0029-5515/49/7/075032
复制
发表时间：
2009
期刊：
影响因子：
3.3
通讯作者：
P. Vasu
中科院分区：
文献类型：
--
作者：
Santanu Banerjee;P. Vasu
本文报道了一个由切向采集的图像反演托卡马克等离子体极向发射率的层析重建程序。在这里，我们提出修改的代码，占任何漫反射从表面的墙壁包围等离子体。通常认识到，这样的重构码对数据中的噪声非常敏感。在这项工作中，我们分析了不同程度的超确定性的方程组中的噪声的灵敏度;超确定性被定义为可用的检测器信号的数量与重建的网格分辨率的比率。一个易于处理的计划划分成一个有限数量的未知的子环面和空隙的极向截面，同时仍然保持高的超确定性，被纳入。最后，它表明，噪声水平>20%，可以处理从目前的检测器阵列/相机实现的超确定性。这里使用的矩阵的奇异值分解，可以预期收敛，即使遇到任何病态矩阵，由于通过子环面和空隙的弦长估计的计算舍入误差。
A tomographic reconstruction code had been reported by us for inferring the poloidal emissivity of tokamak plasma from tangentially acquired images. Here we present modifications to the code that account for any diffuse reflections from the surfaces of walls enclosing the plasma. It is generally recognized that such reconstruction codes are highly susceptible to noise in the data. In this work we have analysed the sensitivity to noise for varying degrees of over-determinism in the set of equations; over-determinism is defined as the ratio of the number of detector signals available to the grid resolution of reconstruction. A tractable scheme for dividing the poloidal cross section into a finite number of unknown sub-tori and voids, while still keeping the over-determinism high, is incorporated. Finally it is shown that noise level >20% can be handled with over-determinism achievable from present day detector array/cameras. The singular value decomposition of the matrix, as used here, can be expected to converge even if any ill-conditioned matrix is encountered due to computational round-off errors in the estimation of chord lengths through sub-tori and voids.