Bluesky NeXus: a solution for NeXus-compliant data acquisition in Bluesky

Modern scientific experiments require rich, standardized metadata to ensure data is Findable, Accessible, Interoperable, and Reusable (FAIR). The NeXus format—a hierarchical data standard used in neutron, x-ray, and muon science—provides a structured way to organize such metadata, but integrating it automatically into acquisition workflows remains a challenge. We present Bluesky NeXus, a Python package that enables automated, standards-compliant NeXus data generation within Bluesky—a modular Python-based framework for experiment control and data acquisition widely used at synchrotron and neutron facilities. Users define the desired NeXus structure—including groups, datasets, and attributes—using human-readable configuration files (YAML schemas), which are validated using models defined with Pydantic, a Python library for data validation, to ensure consistency and adherence to NeXus definitions. This enables flexible, user-defined metadata management while preserving data integrity. Bluesky NeXus gathers static metadata (e.g., equipment setup) and dynamic data (e.g., measurements), consolidating them into a complete NeXus file automatically archived with each experiment. It integrates with deployment tools like the Bluesky container used at BESSY II and supports diverse experimental configurations. Developed within the ROCK-IT project, Bluesky NeXus streamlines the creation of standardized metadata, advancing the Interoperability and Reusability goals of the FAIR principles.