A von Hamos full-cylindrical spectrometer based on striped Si/Ge crystal for advanced x-ray spectroscopy.

High-energy resolution core-level spectroscopies, including a group of different techniques to obtain element-specific information of the electronic structure around an absorption site, have become powerful tools for studying the chemical state, local geometric structure, and the nature of chemical bonding. High-resolution x-ray absorption and x-ray emission spectroscopies are well-established experimental techniques but have always been limited by the number of emitted photons and the limited acceptance of solid angles, as well as requiring high energy stability and repeatability for the whole experimental setup. A full-cylindrical x-ray spectrometer based on flexible HAPG (highly annealed pyrolitic graphite) mosaic crystals is an effective solution for the above issues.

Effect of Vacancy Behavior on Precipitate Formation in a Reduced-Activation V-Cr-Mn Medium-Entropy Alloy.

In this work, we studied the evolution of vacancy-like defects and the formation of brittle precipitates in a reduced-activation V-Cr-Mn medium-entropy alloy. The evolution of local electronic circumstances around Cr and Mn enrichments, the vacancy defects, and the CrMn precipitates were characterized by using scanning electron microscopy with energy-dispersive spectroscopy, X-ray diffraction, and positron annihilation spectroscopy. The microstructure measurements showed that the Mn and Cr enrichments in the as-cast sample significantly evolved with temperature, i.

Characteristics of Solar Wind Radiation Damage in Lunar Soil: PAT and TEM Study.

Irradiation structural damage (e.g., radiation tracks, amorphous layers, and vesicles) is widely observed in lunar soil grains.

Study of Interaction Mechanism between Positrons and Ag Clusters in Dilute Al-Ag Alloys at Low Temperature.

The microstructural evolution of dilute Al-Ag alloys in its early aging stage and at low temperatures ranging from 15 K to 300 K was studied by the combined use of Positron annihilation lifetime spectroscopy (PALS), high resolution transmission electron microscopy (HRTEM), and positron annihilation Coincidence Doppler broadening (CDB) techniques. It is shown that at low temperatures below 200 K, an Ag-vacancy complex is formed in the quenched alloy, and above 200 K, it decomposes into Ag clusters and monovacancies. Experimental and calculation results indicate that Ag clusters in Al-Ag alloys can act as shallow trapping sites, and the positron trapping rate is considerably enhanced by a decreasing measurement temperature.

Insight into structural stability and helium diffusion behavior of Fe-Cr alloys from first-principles.

We have performed the first-principles method to study the structural stability and helium diffusion behavior of Fe-Cr alloys. The calculated bulk modulus of 284.935 GPa in the non-magnetic (NM) state is in good agreement with others.

Investigation of Helium Behavior in RAFM Steel by Positron Annihilation Doppler Broadening and Thermal Desorption Spectroscopy.

The behavior of helium in reduced-activation ferritic/martensitic steels was investigated systematically with positron annihilation Doppler broadening measurement and thermal desorption spectroscopy. Specimens were irradiated with helium ions with different energies to various fluences at different temperatures. A threshold fluence was observed above which the rate of formation and growth of helium bubbles dramatically increased.