合肥先进光源储存环初步物理设计

我国最近立项建设的合肥先进光源将是一台软X射线与真空紫外衍射极限储存环光源,其电子束能量为2.2 GeV,周长为480 m,束流自然发射度为86 pm·rad,共有20个长直线节和20个短直线节。介绍了目前合肥先进光源储存环物理设计的进展情况,包括磁聚焦结构设计与优化,束流注入和集体效应的模拟与计算。     

Propagation of terahertz waves in nonuniform plasma slab under "electromagnetic window"

The application of magnetic fields, electric fields, and the increase of the electromagnetic wave frequency are up-and-coming solutions for the blackout problem. Therefore, this study considers the influence of the external magnetic field on the electron flow and the effect of the external electric field on the electron density distribution, and uses the scattering matrix method (SMM) to perform theoretical calculations and analyze the transmission behavior of terahertz waves under different electron densities, magnetic field distributions, and collision frequencies. The results show that the external magnetic field can improve the transmission of terahertz waves at the low-frequency end. Magnetizing the plasma from the direction perpendicular to the incident path can optimize the right-hand polarized wave transmission. The external electric field can increase the transmittance to some extent, and the increase of the collision frequency can suppress the right-hand polarized wave cyclotron resonance caused by the external magnetic field. By adjusting these parameters, it is expected to alleviate the blackout phenomenon to a certain extent.     

Collision site effect on the radiation dynamics of cytosine induced by proton

By combing the time-dependent density functional calculations for electrons with molecular dynamics simulations for ions (TDDFT-MD) nonadiabatically in real time, we investigate the microscopic mechanism of collisions between cytosine and low-energy protons with incident energy ranging from 150 eV to 1000 eV. To explore the effects of the collision site and the proton incident energy on irradiation processes of cytosine, two collision sites are specially considered, which are N and O both acting as the proton receptors when forming hydrogen bonds with guanine. Not only the energy loss and the scattering angle of the projectile but also the electronic and ionic degrees of freedom of the target are identified. It is found that the energy loss of proton increases linearly with the increase of the incident energy in both situations, which are 14.2% and 21.1% of the incident energy respectively. However, the scattering angles show different behaviors in these two situations when the incident kinetic energy increases. When proton collides with O, the scattering angle of proton is larger and the energy lost is more, while proton captures less electrons from O. The calculated fragment mass distribution shows the high counts of the fragment mass of 1, implying the production of H⁺ fragment ion from cytosine even for proton with the incident energy lower than keV. Furthermore, the calculated results show that N on cytosine is easier to be combined with low-energy protons to form NH bonds than O.     

New experimental measurement of natSe(n, γ) cross section between 1 eV to 1 keV at the CSNS Back-n facility

The ⁷⁴Se is one of 35 p-nuclei, and ⁸²Se is a r-process only nucleus, and their (n, γ) cross sections are vital input parameters for nuclear astrophysics reaction network calculations. The neutron capture cross section in the resonance range of isotopes and even natural selenium samples has not been measured. Prompt γ-rays originating from neutron-induced capture events were detected by four C₆D₆ liquid scintillator detectors at the Back-n facility of China Spallation Neutron Source (CSNS). The pulse height weighting technique (PHWT) was used to analyze the data in the 1 eV to 100 keV region. The deduced neutron capture cross section was compared with ENDF/B-VIII.0, JEFF-3.2, and JENDL-4.0, and some differences were found. Resonance parameters were extracted by the R-matrix code SAMMY in the 1 eV-1 keV region. All the cross sections of ^natSe and resonance parameters are given in the datasets. The datasets are openly available at http://www.doi.org/10.11922/sciencedb.j00113.00019.     

Growth and characterization of superconducting Ca1-xNaxFe2As2 single crystals by NaAs-flux method

High-quality superconducting Ca$_{1-x}$Na$_x$Fe$_2$As$_2$ single crystals have been successfully grown by the NaAs-flux method, with sodium doping level $x = 0.4$-0.64. The typical sizes of these crystals are more than 10 mm in $ab$-plane and $\sim 0.1$ mm along $c$-axis in thickness. X-ray diffraction, resistance and magnetization measurements are carried out to characterize the quality of these crystals. While no signature of magnetic phase transitions is detected in the normal state, bulk superconductivity is found for these samples, with a sharp transition at $T_{\rm c}$ ranging from 19.8 K ($x = 0.4$) to 34.8 K ($x = 0.64$). The doping dependences of the $c$-axis parameter and $T_{\rm c}$ are consistent with previous reports, suggesting a possible connection between the lattice parameters and superconductivity.     

Periodic and chaotic oscillations in mutual-coupled mid-infrared quantum cascade lasers

Dynamic states in mutual-coupled mid-infrared quantum cascade lasers (QCLs) were numerically investigated in the parameter space of injection strength and detuning frequency based on the Lang—Kobayashi equations model. Three types of period-one states were found, with different periods of injection time delay τ_inj, 2τ_inj, and reciprocal of the detuning frequency. Besides, square-wave, quasi-period, pulse-burst and chaotic oscillations were also observed. It is concluded that external-cavity periodic dynamics and optical modes beating are the mainly periodic dynamics. The interaction of the two periodic dynamics and the high-frequency dynamics stimulated by strong injection induces the dynamic states evolution. This work helps to understand the dynamic behaviors in QCLs and shows a new way to mid-infrared wide-band chaotic laser.     

互动新媒体中的即时通信业务应用进展

对互动新媒体网络中的即时通信业务进行了阐述,介绍了其应用进展,指出了新型即时通信业务的内涵,分析了互动新媒体中的即时通信业务的实际社会和经济效益,详细阐述了互动新媒体中即时通信业务需要解决的问题和基本的解决思路.互动新媒体中的即时通信业务将成为融合网络和未来新媒体经济的重要推动力.     

EC9706细胞经不同剂量X射线辐照后的拉曼光谱

为了研究不同剂量X射线对食管癌(EC9706)细胞的辐射损伤,经不同剂量X射线照射后继续培养24 h,利用拉曼光谱分析其内部蛋白质、核酸、脂类等构象和含量变化.实验结果表明,各剂量组拉曼光谱的峰强和频移与空白对照组之间存在较大的差异.对照组光谱中某些谱带在个别剂量组消失,如蛋白质主链中C-N振动1114 cm-1谱带在各剂量组中消失,脱氧核糖Dr振动谱带895 cm-1仅存在于8Gy组,937 cm-1谱带仅存在于12Gy组,膜脂中膜结合β-胡萝卜素的C=C振动谱带1523 cm-1仅存在于6Gy组.这些特征谱带在不同剂量组光谱中的变化,为进一步研究X射线辐照EC9706细胞的最佳剂量提供了一定参考.     

J-TEXT托卡马克高速单色成像系统研制

在J-TEXT托卡马克上研制了一套高速单色成像系统用于研究等离子体杂质行为与磁流体力学(MHD)不稳定性之间的关系.用STRAH代码模拟估算了碳杂质(CV227.09nm,CIII464.7nm)辐射强度.采用光纤耦合方法设计了系统光路结构,光路覆盖高场侧区域0.3a～0.95a(a为小半径),其空间分辨率为1.3cm...     

钕敏化多层壳纳米结构的增强型染料敏化上转换发光

对于稀土离子掺杂的上转换发光,由于稀土离子吸收截面小、吸收范围窄,导致其发光强度受限.最近,在稀土上转换纳米粒子的表面连接近红外染料分子敏化发光,被证实是提高上转换发光强度的有效策略.然而,将染料分子连接经典的稀土Yb掺杂纳米粒子,并不能有效利用染料分子的敏化能力.针对这一问题,本文通过高温热分解法成功制备了Nd3+敏...