A robotic goniometer exchanger for high-throughput single-crystal X-ray diffraction at SPring-8

Rapid and reliable sample handling is essential for high-throughput single-crystal diffraction at modern synchrotron facilities. At the high-energy single-crystal X-ray diffraction beamline BL02B1 of SPring-8, a compact six-axis robotic arm was implemented as a diffractometer for single-crystal measurements using high-energy X-rays. Coordinated six-axis motion enables virtual rotation about an arbitrary axis and reproduction of a conventional ω-scan geometry without additional rotary stages. Under identical beam conditions (180 µm × 113 µm), the robotic-arm system yielded diffraction data with an internal agreement factor of R_int = 0.117, comparable with that obtained using a conventional goniometer (R_int = 0.134). Optical microscopy and diffraction analysis indicate a positional deviation of approximately ±17 µm during ω-scans, with a standard deviation of the spindle position of 0.14°. Although this accuracy is lower than that of high-precision single-crystal goniometers, it is sufficient for diffraction experiments employing large beam sizes and high-energy X-rays. Owing to its compact design, programmable motion control and open geometry, the system provides a flexible platform for automated sample handling and high-throughput diffraction experiments in support of the SPring-8-II upgrade.