A laser heating diamond anvil cell system for high-pressure nuclear resonant scattering at 3-ID, APS.

Nuclear resonant scattering (NRS) provides the basis for powerful synchrotron-based techniques, including synchrotron Mössbauer spectroscopy (SMS) and nuclear resonant inelastic x-ray scattering (NRIXS), which probe the elastic, magnetic, thermodynamic, and vibrational properties of iron-bearing materials and are, therefore, well suited for studying the structure and composition of Earth's and planetary interiors. Here, we report the development and commissioning of a double-sided laser heating system for diamond anvil cell experiments at the 3-ID beamline of the Advanced Photon Source (APS). A key feature of the system is a 7° offset between the x-ray and laser-delivery paths, which positions the near-sample mirrors outside the x-ray path. This design minimizes x-ray absorption, enhances the NRS signal rate during laser heating, improves imaging quality, and significantly reduces thermal drift during extended data acquisition periods. The setup is optimized to match the reduced x-ray beam size available after the APS upgrade, making NRS measurements under extreme pressure-temperature conditions more practical. In addition, the system supports complementary online ruby fluorescence and x-ray diffraction measurements for characterizing samples before and after laser heating. We demonstrate the performance of the system through representative SMS and NRIXS measurements conducted under simultaneous high-pressure and high-temperature conditions.