In situ X-ray diffraction study of point defects in neptunium dioxide at elevated temperature

Lattice thermal expansion of NpO₂ has been measured up to 2000 K by in situ X-ray diffraction. Above 1643 K, the departure from linearity is interpreted on the basis of the calculation of the vacancy formation energy from the oxygen Debye temperature, as a combination of chemical reduction into NpO_2-x and the development of oxygen Frenkel pairs.

All-diamond optical assemblies for a beam-multiplexing X-ray monochromator at the Linac Coherent Light Source

All-diamond optical assemblies holding state-of-the-art type IIa diamond crystals enable the construction of a beam-multiplexing X-ray double-crystal monochromator for hard X-ray free-electron lasers. Details on the design, fabrication and X-ray diffraction characterization of the assemblies are reported.