Multi-axis diamond anvil cell (MDAC) as a triaxial deformation apparatus for high pressure studies

We describe the use of a multi-axis diamond anvil cell (MDAC) as a triaxial deformation apparatus for high-pressure studies with in situ synchrotron x-ray diagnostics. The MDAC employs six independently driven diamond anvils in a cubic geometry, enabling near-uniform compression to high pressures followed by controlled differential loading along orthogonal axes. This architecture largely decouples pressure generation from deviatoric stress application-a persistent limitation of conventional diamond anvil cells (DACs)-and provides independent control of the stress path. We present the experimental methodology, including lattice-strain analysis adapted for the MDAC geometry, sample-strain measurement using combined encoder readings and x-ray radiography, texture analysis, and detector calibration for modular area detectors. The capabilities of the device are demonstrated through deformation experiments on polycrystalline MgO at ∼12 GPa. The MDAC preserves a nearly texture-free sample state during initial near-uniform compression and resolves the onset of lattice preferred orientation development, lattice-strain reflection ordering and its reversal upon yielding, and subsequent plastic evolution. Comparison with results from deformation-DIA and conventional DAC experiments in the literature indicates that the MDAC can access deformation states that are difficult to isolate in existing devices. The instrument is applicable to a broad range of materials that require controlled multi-axis stress states at high pressure and simultaneous structural and textural characterization.