MA-XRF Scanner: Implementation of Elemental Maps Reconstruction Algorithm Based on Single Photon Detection for Cultural Heritage Studies

Recent advancements in data acquisition hardware and online digital pulse processing facilitate real-time detection and timestamping of single photons with nanosecond-level resolution. The integration of this technology with a precision movement system facilitates conditions for developing innovative image reconstruction algorithms, thereby enhancing traditional methods. Moreover, the active system control enables stable and safe scanning by maintaining a constant distance from the surface of the object while ensuring uniformity in the photon collection. This paper outlines the design and development of an MA-XRF scanner for cultural heritage studies, along with the presentation of an elemental map reconstruction algorithm based on single-photon mapping, highlighting its advantages and limitations. The scanner is based on a three-axis system covering an inspection range of 510 mm in X and Y axis and 50 mm in the Z axis, with 10 μm effective step resolution. Additionally, it incorporates a laser proximity sensor, allowing for dynamic distance-to-surface adjustment with a precision of 10 μm. The X-ray beam can be collimated to a spot size of 600 or to 185 μm by using a polycapillary lens positioned 1 mm from the surface. The mechanical system is synchronized with the photon collection performed by a silicon drift detector with an energy range from characteristic XRF lines of Sulphur (2.308 keV) to Barium (32.19 keV), and a multichannel analyzer operating in time-list mode (TLIST), with a timestamp resolution of 40 ns. The resulting elemental map allows for image reconstruction with different pixel sizes selected by the user. The system is controlled by an Application Programming Interface (API) developed in Python, allowing for seamless integration with a Jupyter Notebook server for remote operation. This collaborative effort between the Multidisciplinary Laboratory (MLAB) of the Abdus Salam International Centre of Theoretical Physics (ICTP) and the Nuclear Science and Instrumentation Laboratory (NSIL) of the International Atomic Energy Agency (IAEA) aims to advance research capabilities in cultural heritage studies.