Investigation of two-photon electron capture by H-like uranium

We present a study of two-photon electron capture by H-like uranium ions. The energy of the incident electron was chosen to be in the region with the most significant contribution of the dielectric recombination. We studied the photon emission spectrum, including the main resonance groups corresponding to the cascade transition, and the low-energy photon region, where the infrared divergence required special processing. The calculations were performed within the framework of QED theory. The importance of generalized Breit interaction was discussed. We investigated the roles of the dielectric recombination and the radiative recombination. We introduced and investigated the resonance approximation and the single-photon approximation, which are commonly used to describe radiation spectra

Production and decay of K-shell hollow krypton in collisions with 52 - 197 MeV/u bare xenon ions

X-ray spectra of K-shell hollow krypton atoms produced in single collisions with 52 - 197 MeV/u Xe54+ ions are measured in a heavy-ion storage ring equipped with an internal gas-jet target. Energy shifts of the K{\alpha}_1,2^s, K{\alpha}_1,2^(h,s), and K\b{eta}_1,3^s transitions are obtained. Thus, the average number of the spectator L-vacancies presented during the x-ray emission is deduced. From the relative intensities of the K{\alpha}_1,2^s and K{\alpha}_1,2^(h,s) transitions, the ratio of K-shell hollow krypton to singly K-shell ionized atoms is determined to be 14 - 24%. In the considered collisions, the K-vacancies are mainly created by the direct ionization which cannot be calculated within the perturbation descriptions. The experimental results are compared with a relativistic coupled channel calculation performed within the independent particle approximation.Comment: 5 figures, 9 pages. Accepted by Physical Review

Morphology control of hexagonal strontium ferrite micro/nano-crystals

In this study, controllable morphology evolution of hexagonal strontium ferrite (SrFe12O19) micro/nano-crystals has been demonstrated. Single phase strontium ferrite platelets with hexagonal morphology were successfully prepared by conventional ceramic process. In the hexagonal crystals, it is revealed that the anisotropic growth rate is changed, with the increasing of ball milling time, from relatively high rate along the direction (c-axis) to direction, leading to the morphology evolution. Moreover, the optimal saturation magnetization (MS) is 69.5 emu/g, which is intensely close to the theoretical value (72 emu/g). This study provides the direct evidence of the enhanced reaction activity induced by high energy ball milling in strontium hexaferrite platelets and the obtained SrFe12O19 particles are promising for the hard magnet application and the magnetoelectric electronics

Research on the influence of a high proportion of wind power connected to the receiving power grid on the system power angle stability

With the increasing proportion of wind power integration, the effect on the stability of the system power angle cannot be ignored. In this paper, based on the different power characteristics of direct-drive wind generators before a fault and after its clearance, the system model of the receiving-end grid with thermal units replaced by wind turbines is simplified. The influence of the increase in the replacement ratio of wind power in the receiving-end grid on the transfer impedance between the sending end and receiving end is analyzed. Based on the equal area rule, the influence of the replacement ratio k within the receiving-end grid, power grid operation mode, and wind power integration point on the system power angle stability is analyzed. It is concluded that the stability of the system’s power angle will first get better and then deteriorate with the increase in the replacement ratio of wind power, the system can bear a larger proportion of wind turbines under the low-load operation mode, and the system’s power angle of the replacement of wind power with equal capacity in the load center region is relatively better. The aforementioned conclusions are verified by simulation with real data from a bulk power system in China. Therefore, the method and conclusion can also be used to study the power angle stability of other large-scale power grids