The design of a data management system at HEPS.

According to the estimated data rates, it is predicted that 24 PB raw experimental data will be produced per month from 14 beamlines at the first stage of the High-Energy Photon Source (HEPS) in China, and the volume of experimental data will be even greater with the completion of over 90 beamlines at the second stage in the future. To make sure that the huge amount of data collected at HEPS is accurate, available and accessible, an effective data management system (DMS) is crucial for deploying the IT systems. In this article, a DMS is designed for HEPS which is responsible for automating the organization, transfer, storage, distribution and sharing of the data produced from experiments. First, the general situation of HEPS is introduced. Second, the architecture and data flow of the HEPS DMS are described from the perspective of facility users and IT, and the key techniques implemented in this system are introduced. Finally, the progress and the effect of the DMS deployed as a testbed at beamline 1W1A of the Beijing Synchrotron Radiation Facility are shown.

Neutron powder-diffraction study of phase transitions in strontium-doped bismuth ferrite: 1. Variation with chemical composition.

We report results from a study of the crystal and magnetic structures of strontium-doped BiFeO3using neutron powder diffraction and the Rietveld method. Measurements were obtained over a wide range of temperatures from 300-800 K for compositions between 10%-16% replacement of bismuth by strontium. The results show a clear variation of the two main structural deformations-symmetry-breaking rotations of the FeO6octahedra and polar ionic displacements that give ferroelectricity-with chemical composition, but relatively little variation with temperature. On the other hand, the antiferromagnetic order shows a variation with temperature and a second-order phase transition consistent with the classical Heisenberg model. There is, however, very little variation in the behaviour of the antiferromagnetism with chemical composition, and hence with the degree of the structural symmetry-breaking distortions. We therefore conclude that there is no significant coupling between antiferromagnetism and ferroelectricity in Sr-doped BiFeO3and, by extension, in pure BiFeO3.

Atomic pair distribution function research on Li2MnO3 electrode structure evolution.

The mechanism research of structure-related reactions on Li2MnO3 is important to enhance the electrochemical performance of lithium-manganese-rich layered oxides. Although there are some reports on the structure evolution of Li2MnO3 during cycling process, the employed research techniques are very limited, mainly in/ex-situ X-ray diffraction, X-ray absorption and transmission electron microscopy. Here, atomic pair distribution function, a method to study the local atomic arrangement on the basis of average spectroscopic information, is used for the first time to study the local structure evolution of Li2MnO3 during electrochemical charge/discharge cycles. The results clearly demonstrate that Mn3+/Mn4+ redox couple is activated and Mn ions are reduced during discharging process. Some Mn ions in Mn layers can significantly migrate to Li layers and occupy the octahedral sites. As a result, a portion of inserted Li ions can occupy the face-shared tetrahedronsites, accompanied by the formation of local spinel-like structure. This work provides an important and suitable method based on the average spectroscopic information to investigate the local structure of electrode materials of lithium-ion batteries as well as other advanced battery systems.