Data for publication: 3D local measurement of the magnetic field strength inside Martian meteorite NWA 7034 by polarimetric neutron imaging

The following files contain the relevant data and analysis notebooks used for the work pertaining the article: "3D local measurement of the magnetic field strength inside Martian meteorite NWA 7034 by polarimetric neutron imaging"Analysis was done by Cédric Qvistgaard: https://orcid.org/0009-0007-3341-4508Authors: Cédric Holme Qvistgaard, Estrid Buhl Naver, Alexander Wolfertz, Vahid Karimi, Takenao Shinohara, Joseph Don Parker, Tetsuya Kai, Hirotoshi Hayashida, Søren Schmidt, and Luise Theil Kuhn.Neutron polarimetric imaging performed of a sample of meteorite North West Africa (NWA) 7034 at the RADEN beamline at JPARC in Japan.It should contain 2 notebooks,1 tiff file and 4 npy files.Rock1_Stack.npy is the polarization images for each tomography angle and component. It should be a 33 x 9 x 128 x 128 voxel grid, with 33 angles spanning 0 to 360 degrees evenly, and the 9 matrix components [Pxx,Pxy,Pxz,Pyx,Pyy,Pyz,Pzx,Pzy,Pzz]. CCBY-4.0 (https://creativecommons.org/licenses/by/4.0/)Rock1_Stack_Cut.npy is a cut 80 x 80 ROI version used for the reconstruction. CCBY-4.0Structure_Recon_rot.tiff contains the structure reconstructed from the attenuation images. CCBY-4.0B_MSE.tiff is the final reconstruction that we have used for further plotting etc.CCBY-4.0Raden_Beam_Profile.npy shows the wavelength profile of the beam, in case a more accurate ToF weighted reconstruction would be needed. This does drastically increase computing power required though. CCBY-4.0Iterative Solver Mars Rock.ipybn is the document wherein most of the analysis was done. In broad strokes it:- Initiates the GPU, and finds the mean wavelength of the beam.- Defines the forward simulation via PNI_experiment, which simply loops through each voxel and updates the spin orientation of each pixel accordingly.- Defines an optimizer which utilizes gradient descent backpropagation and the ADAM optimizer from pytorch to "guess" new structures until the forward agrees with our measurements.- Defines some plotting functions to compare simulated components with measurements, and produce a 3D plot.Copyright @ Technical University of Denmark, BSD-3-Clause (https://opensource.org/license/bsd-3-clause)The notebook "Comparison and visualization.ipybn" contains further plotting functions utilized, such as the slice quiver plot. However, for most purposes the "iterative solver" document can be run alone.Copyright @ Technical University of Denmark, BSD-3-Clause以下文件涵盖了与发表论文《通过极化中子成像（polarimetric neutron imaging）对火星陨石NWA 7034内部磁场强度开展三维局部测量》相关的实验数据与分析脚本。 分析工作由Cédric Qvistgaard完成：https://orcid.org/0009-0007-3341-4508。 作者名单如下：Cédric Holme Qvistgaard、Estrid Buhl Naver、Alexander Wolfertz、Vahid Karimi、Takenao Shinohara、Joseph Don Parker、Tetsuya Kai、Hirotoshi Hayashida、Søren Schmidt 及 Luise Theil Kuhn。 研究团队在日本质子加速器研究复合体（Japan Proton Accelerator Research Complex, JPARC）的RADEN束线对西北非洲（North West Africa, NWA）7034陨石样品开展了中子极化成像实验。 本数据集包含2份Jupyter笔记本（Jupyter notebook）、1个TIFF文件与4个NPY文件。 Rock1_Stack.npy存储了各断层扫描角度与分量下的极化图像，其为33×9×128×128的体素网格（voxel grid）：其中33个角度均匀覆盖0至360度范围，9个矩阵分量分别为[Pxx, Pxy, Pxz, Pyx, Pyy, Pyz, Pzx, Pzy, Pzz]。本文件采用CC BY 4.0许可协议（https://creativecommons.org/licenses/by/4.0/）。 Rock1_Stack_Cut.npy为用于重建的80×80感兴趣区域（Region of Interest, ROI）裁剪版本，采用CC BY 4.0许可协议。 Structure_Recon_rot.tiff存储了由衰减图像重建得到的样品结构图像，采用CC BY 4.0许可协议。 B_MSE.tiff为用于后续绘图等分析的最终重建结果，采用CC BY 4.0许可协议。 Raden_Beam_Profile.npy记录了中子束的波长分布，以供需要更精确的飞行时间（Time of Flight, ToF）加权重建时使用，但该操作会显著提升计算资源需求。本文件采用CC BY 4.0许可协议。 Iterative Solver Mars Rock.ipybn为完成大部分分析工作的核心脚本，其主要功能包括： 1. 初始化图形处理器（Graphics Processing Unit, GPU）并计算中子束的平均波长； 2. 通过PNI_experiment定义前向模拟流程，即遍历每个体素并依次更新各像素的自旋取向； 3. 定义优化器：结合梯度下降反向传播（gradient descent backpropagation）与PyTorch内置的ADAM优化器，迭代生成新的样品结构，直至前向模拟结果与实测数据匹配； 4. 定义若干绘图函数，用于对比模拟分量与实测数据，并生成三维可视化图像。 本脚本版权归丹麦技术大学所有，采用BSD-3-Clause许可协议（https://opensource.org/license/bsd-3-clause）。 Comparison and visualization.ipybn包含额外的绘图功能，例如切片箭图（slice quiver plot）。不过在多数场景下，仅运行Iterative Solver Mars Rock.ipybn脚本即可完成分析。本脚本版权归丹麦技术大学所有，采用BSD-3-Clause许可协议。