VIPR - Versatile Framework for Inverse Problems
The Problem: Reconstruction of hidden material properties from complex measurement data
Working with the neutron reflectometer creates a physically demanding inverse problem: from noisy reflectivity measurement data, central material properties such as layer thickness, roughness, or density profiles must be reconstructed. Together with MLZ Instrument Scientist Dr. Alexandros Koutsiumpas, the entire measurement and analysis process was examined. The challenge is to read the machine's data almost in real-time, automatically select the appropriate pre-trained model from metadata, and reliably feed the analysis results back into the experimental workflow – for example, for in-situ machine control. At the same time, the results should be visualized in an understandable and user-friendly way via a frontend.
The Solution Approach: Invertible neural networks for fast and robust reconstructions
An invertible neural network enables direct solution of the inverse problem: it learns the mapping between measurement data and material properties in a way that this relationship remains unique and reversible. This allows the model to directly infer the underlying material parameters from noisy reflectivity curves – without time-consuming iterative simulations. Through automated selection of a suitable, pre-trained model, new measurement data can be analyzed immediately, while the web interface allows even non-specialists to intuitively experiment with different models and compare their results.
The Result: Dramatic acceleration and better usability in the research process
This approach achieved a 195-fold acceleration: analysis time dropped from around 185 seconds to about 1 second – fast enough for real-time applications. The results can be immediately fed into automated workflows, allowing machines to be dynamically adjusted during measurement. At the same time, the intuitive web visualization ensures that both experts and non-specialists can efficiently evaluate the data and immediately assess measurement quality. This creates a powerful and practical solution that demonstrates how modern invertible neural networks can solve complex technical challenges in practice.





