# Particle Fingerprint: X-ray CT of Lunar Regolith Simulants and Simulation Data

## General Remark ##
This dataset is associated with the follwoing publication and contains the particle-resolved data and derived descriptors used for the development and evaluation of the Particle System Fingerprint (PSF) methodology. Since the name of the data set cannot be changed, there is an inconsistency between the final publication and the published data set. Particle fingerprint and particle system fingerprint are synonymous in this context.

**Particle System Fingerprint (PSF): A New Approach to Visualize and Compare Large-Scale Particle–Discrete Phase Information**

*The particle system fingerprint (PSF) is a new visualization technique designed to analyze large--scale particle--discrete data sets efficiently. Computed tomography (CT) data sets provide a wide range of information for each individual particle, including geometric parameters as well as detailed insights into composition and internal structure derived from gray value distributions. The PSF transforms individual gray value histograms into stacked and sorted 2D patterns, encoding frequency data into gray scale for intuitive interpretation. Using X--ray tomography data sets, such as lunar regolith simulants, this method effectively highlights compositional variations across thousands of particles while maintaining key distribution features. Lunar regolith simulants represent a technologically relevant and inherently heterogeneous granular material, providing a demanding test case in terms of structural complexity and compositional variability. The approach is particularly suited for applications such as quality control, process monitoring, and overview analysis of complex particle systems, as demonstrated using the example of statistical process control (SPC)*

Ralf Ditscherlein, Thomas Buchwald, Urs A. Peuker  
Technische Universität Bergakademie Freiberg  
Institute of Mechanical Process Engineering and Mineral Processing  
Agricolastraße 1  
D-09599 Freiberg  
Germany  

## X-ray CT Equipment

All X-ray tomography scans were performed using a **Zeiss Xradia Versa 510 micro-CT system**. Voxel size was 2 µm, acquired at 4× magnification. Detailed measurement parameter description is given below (**Dataset Structure**). Raw CT gray values are normalized to an 8-bit grayscale range (0–255), representing increasing X-ray attenuation. The normalization is referenced to the global maximum gray value across all measurements to ensure consistent scaling between datasets. A higher bit depth (e.g., 16-bit) is not appropriate, as most particles contain insufficient voxel counts to justify a larger number of classes. Excessive binning leads to over-binning, causing fragmented bins, increased noise, and reduced interpretability of the gray value distribution.

## Sample Material
The dataset includes four **lunar regolith simulants**, selected to represent mare and highland regions:

- **JSC-1A** (mare simulant)  
  - NASA ARES project page (description, properties): https://ares.jsc.nasa.gov/projects/simulants/jsc-1-1a.html  
  - Characterization report (Lunar simulant data): https://www.lpi.usra.edu/lunar/strategies/jsc_lunar_simulant.pdf  

- **LMS-1** (mare simulant)  
  - Product/specification page (Space Resource Technologies): https://spaceresourcetech.com/products/lms-1-lunar-mare-simulant  

- **LHS-1** (highland simulant)  

   - Product/specification page (Space Resource Technologies): https://spaceresourcetech.com/products/lhs-1-lunar-highlands-simulant

- **OB-1A** (highland simulant)  
  - NASA ARES project page (OB-1 series summary): https://ares.jsc.nasa.gov/projects/simulants/ob-1.html  
  - NASA Lunar Regolith Simulant User’s Guide (contains OB-1 info, PDF): https://ntrs.nasa.gov/api/citations/20240011783/downloads/Lunar_Regolith_Simulant_Users_Guide_Rev_A_28OCT.pdf  


The referred metadata is also provided as pdf. The samples were embedded with carbon black spacer particles to avoid clustering and sedimentation, enabling reliable particle-discrete segmentation (https://doi.org/10.1016/j.powtec.2021.09.038).

## Dataset Structure

### 1. Reconstructed raw tomograms
For each regolith simulant, the dataset contains reconstructed image stacks:

- **Format:** 2D TIFF files (`.tiff`), one file per slice.  
- **Additional files:**  
  - `acquisition.PNG` – screenshot of acquisition parameters  
  - `recon.PNG` – screenshot of reconstruction parameters  
  - `preview.PNG` – representative slice for quick overview  

These datasets provide the basis for particle segmentation and subsequent fingerprint generation.

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### 2. PFP simulation
A Jupyter Notebook is provided to demonstrate the simulation and visualization of **Particle Fingerprints (PFP)** and typical imaging artifacts.

- **File:** `PFP_simulation.ipynb`  
- **Purpose:** Reproduces the workflow described in the manuscript, including examples of propagation-based phase contrast (PBPC) and partial volume effects (PVE).  
- **Requirements:** Python ≥ 3.9 with `numpy`, `pandas`, `matplotlib`, `scipy`.  

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### 3. Artificial particle stacks
To illustrate imaging artifacts and their influence on PFPs, artificially generated particle tomograms are included.

- **Files:**  
  - `PBBC_bin1x.tif`, `PBBC_bin2x.tif`, `PBBC_bin4x.tif` (Propagation Based Phase Contrast)  
  - `PVE_bin1x.tif`, `PVE_bin2x.tif`, `PVE_bin4x.tif` (Partial Volume Effect)  
- **Description:** Each stack simulates spherical particle assemblies reconstructed at different binning levels (1×, 2×, 4×). These examples correspond to the artifacts analyzed in the paper.

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### 4. Application Example - Statistical Process Control (SPC)
The provided Jupyter Notebook creates artificial datasets to show a possible application example in industry, where batches of particle systems are analysed over time. The resulting PFP TIFFs are subsequently stacked to a video sequence. Additional alarm thresholds and color lights indicating a critical drift. An introduction to SPC can be found here: https://doi.org/10.1136/qhc.12.6.458.

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## Folder Structure
```
/Dataset
  ├── JSC1A_raw/       # Raw reconstructed tiff stacks + acquisition/recon/preview
  ├── LHS1_raw/
  ├── LMS1_raw/
  ├── OB1A_raw/
  └── material_specs/  # pdf versions of the referred website info
  └── PFP_simulation/
        ├── PFP_simulation.ipynb
        ├── PBBC_bin1x.tif / PBBC_bin2x.tif / PBBC_bin4x.tif
        └── PVE_bin1x.tif / PVE_bin2x.tif / PVE_bin4x.tif
  └── SPC/
        └── SPC_fingerprint.ipynb
        └── SPC_fingerprint.mp4
```

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