Institutional Repository of Institute of Modern Physics, CAS
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4KG-M制冷机做冷源的自循环氦液化装置研制；Development of helium liquefaction self-circulation system with 4 K G-M cryocoolers
No full text采用5台1.5W/4.2KG-M制冷机(日本住友RDK415D)并联研制出了1台方便实验室使用的小型氦液化装置,并为其建立了性能测量实验台。实验结果表明:液氦温度为4.17K(饱和压力为96kPa)时,氦液化率为74L/d;液氦温度为4.42K(饱和压力为121kPa)时,液化率为116L/d,经拟合,在4.2K(饱和压力为100kPa)时液化率为83L/d,并且通过100小时以上的连续运行,说明该氦液化装置自循环性能良好。通过实验发现:实测氦液化率远大于制冷机冷头制冷量对应的计算氦液化率。分析认为:G-M制冷机气缸壁对氦气预冷是提高实际氦液化率的主要因素
PIC mode simulation of solenoid collimation channel
No full textA new SSC (Separated Sector Cyclotron)-Linac is being designed to serve as an injector for the SSC at the HIRFL (Heavy Ion Research Facility Lanzhou). The beam intensity at the LEBT (Low Energy Beam Transport) for the heavy ions after the selection is typically low and the space charge effects are inconspicuous. The space charge effects become obvious when the beam current increases to a few hundred microamperes. The emittance growth deriving from the space charge effects may be particularly troublesome for the following linac and cyclotron. An optical system containing three solenoids has been designed for the LEBT to limit the beam emittance and to avoid the unnecessary beam loss in the cyclotron, as well as for the purpose of immunizing the LEBT emittance growth due to the space charge effects. The results of the PIG (Particle-In-Cell) mode simulation illustrate that this channel could limit the beam emittance growth and increase the beam brightness
Optimal design of a 7 T highly homogeneous superconducting magnet for a Penning trap
No full textA Penning trap system called Lanzhou Penning Trap (LPT) is now being developed for precise mass measurements at the Institute of Modern Physics (IMP). One of the key components is a 7 T actively shielded superconducting magnet with a clear warm bore of 156 mm. The required field homogeneity is 3 x 10(-7) over two 1 cubic centimeter volumes lying 220 mm apart along the magnet axis. We introduce a two-step method which combines linear programming and a nonlinear optimization algorithm for designing the multi-section superconducting magnet. This method is fast and flexible for handling arbitrary shaped homogeneous volumes and coils. With the help of this method an optimal design for the LPT superconducting magnet has been obtained
Study on shunt impedance and voltage distribution of 4-rod RFQ cavity
No full textA high current RFQ (radio frequency quadrupole) is being studied at the Institute of Modern Physics, CAS for the direct plasma injection scheme. Shunt impedance is air important parameter when designing a 4-rod RFQ cavity, it reflects the RF efficiency of the cavity, and has a direct influence on the cost of the structure. Voltage distribution of a RFQ cavity has an effect on beam transmission, and particles would be lost if the actual voltage distribution is not as what, it should be. The influence of cell length, stern thickness and height on Shunt impedance and voltage distribution have been studied, in particular the effect of projecting electrodes has been investigated in detail
Electron impact excitation rate coefficients of N II ion
No full textThis paper calculates the electron impact excitation rate coefficients from the ground term 2s(2)2p(2) P-3 to the excited terms of the 2s(2)2p(2), 2s2p(3), 2s(2)2p3s, 2s(2)2p3p, and 2s(2)2p3d configurations of N II. In the calculations, rnulticonfiguration Dirac-Fork wave functions have been applied to describe the target-ion states and relativistic distorted-wave calculation has been performed to generate fine-structure collision strengths. The collision strengths are then averaged over a Maxwellian distribution of electron velocities in order to generate the effective collision strengths. The calculated rate coefficients are compared with available experimental and theoretical data, and some good agreements are found for the outer shell electron excitations. But for the inner shell electron excitations there are still some differences between the present calculations and available experiments
Promotion of cooperation in the form C0C1D classified by 'degree grads' in a scale-free network
No full textIn this paper, we revisit the issue of the public goods game (PGG) on a heterogeneous graph. By introducing a new effective topology parameter, 'degree grads' phi, we clearly classify the agents into three kinds, namely, C-0, C-1, and D. The mechanism for the heterogeneous topology promoting cooperation is discussed in detail from the perspective of C0C1D, which reflects the fact that the unreasoning imitation behaviour of C-1 agents, who are 'cheated' by the well-paid C-0 agents inhabiting special positions, stabilizes the formation of the cooperation community. The analytical and simulation results for certain parameters are found to coincide well with each other. The C0C1D case provides a picture of the actual behaviours in real society and thus is potentially of interest
Prototype of the Superferric Dipoles for the Super-FRS of the FAIR-Project
No full textThe FAIR China Group (FCG), consisting of the Institute of Modern Physics (IMP Lanzhou), the Institute of Plasma Physics (ASIPP, Hefei) and the Institute of Electric Engineering (IEE, Beijing) developed and manufactured in cooperation with GSI, Germany a prototype of a superferric dipole for the Super-Fragment-Separator of the FAIR-project [1]. The dipole magnets of the separator will have a deflection radius of 12.5 m, a field up to 1.6 T, a gap of at least 170 mm and an effective length of more than 2 meters to bend ion beams with a rigidity from 2 T . m up to 20 T . m. The magnets operate at DC mode. These requirements led to a superferric design with a yoke weight of more than 50 tons and a maximum stored energy of more than 400 kJ. The principles of yoke, coil and cryostat construction will be presented. We will also show first results of tests and measurements realized at ASIPP and at IMP
Biphasic regulation of H2O2 on angiogenesis implicated NADPH oxidase
No full textROS (reactive oxygen species) take an important signalling role in angiogenesis. Although there are several ways to produce ROS in cells, multicomponent non-phagocytic NADPH oxidase is an important source of ROS that contribute to angiogenesis. In the present work, we examined the effects of H2O2 on angiogenesis including proliferation and migration in HUVECs (human umbilical vein endothelial cells), new vessel formation in chicken embryo CAM (chorioallantoic membrane) and endothelial cell apoptosis, which is closely related to anti-angiogenesis. Our results showed that H2O2 dose-dependently increased the generation of O-2(-) (superoxide anion) in HUVECs, which was suppressed by DPI (diphenylene iodonium) and APO (apocynin), two inhibitors of NADPH oxidase. H2O2 at low concentrations (10 mu M) stimulated cell proliferation and migration, but at higher concentrations, inhibited both. Similarly, H2O2 at 4 nmol/cm(2) strongly induced new vessel formation in CAM, while it suppressed at high concentrations (higher than 4 nmol/cm(2)). Also, H2O2 (200 similar to 500 mu M) could stimulate apoptosis in HUVECs. All the effects of H2O2 on angiogenesis could be suppressed by NADPH oxidase inhibitors, which suggests that NADPH oxidase acts downstream of H2O2 to produce O-2(-) and then to regulate angiogenesis. In summary, our results suggest that H2O2 as well as O-2(-) mediated by NADPH oxidase have biphasic effects on angiogenesis in vitro and in vivo
Studies on the Interaction of Highly Charged Ions with Solid Surfaces and Nanocapillaries
No full text高电荷态离子与固体表面相互作用的研究是目前国际上广受关注的热点研究领域
之一。本论文详细介绍了兰州重离子加速器国家实验室 320 kV高电荷态离子物理综合
研究平台的表面物理实验终端；在实验终端上对高电荷态离子诱导表面产生电子发射、
表面纳米结构形成以及离子在微纳孔箔中的导向传输过程进行了系统的实验研究。得
到的主要结果如下：
1. 电子发射方面，测量了 Heq+， Neq+， Arq+和 Xeq+离子垂直作用于 Si, W和 HOPG
表面产生的电子发射产额。成功分离了单纯势能电子发射产额和动能电子发射
产额。估算出了用于势能电子发射所需势能的份额。通过引入动能电子发射产
额与电子能损的比值 Λ 分析和研究了动能电子发射，结果与半经验理论符合
的很好。首次把 Λ 的研究扩展到高电荷态离子领域，认为 Λ 与入射离子的势
能（电荷态）无关。
2. 表面纳米结构形成方面，用不同电荷态不同入射动能的 Xe离子入射到 HOPG
和云母表面，结合原子力显微镜，扫描隧道显微镜和拉曼光谱，在材料表面观
测到了山峰状纳米尺寸结构的形成。在 HOPG 上产生明显纳米峰的势能阈值
在电荷态为27，而在云母表面上首次发现用Xe29+离子辐照也能产生纳米结构。
纳米峰的高度和宽度随着入射离子势能的增加而增大，而与入射动能没有直接
关系。对石墨表面和云母表面纳米结构形成的机理分别用非弹性热峰模型和库
仑爆炸模型给予了解释。
3. 离子与微纳孔箔作用方面，用一维和二维位置灵敏探测器测量和分析了 Neq+和 Xeq+
穿过 150nm 和 250nm 多孔箔和单纳米孔后出射离子的时间效应、电荷
态分布、离子产额的角度分布和表征导向能力的临界角。研究了微纳孔箔后
表面带电和入射离子束流强度对离子传输的影响。我们首次研究了离子在单
个纳米孔内的传输过程。证实了单孔内存在导向效应，提出了单孔箔导引离
子应用的可能。用导向效应对实验结果进行了定量的解释
Study of aqueous chemical properties of homologs of superheavy elements Sg and Rf
No full text超重元素的化学性质研究是核化学研究领域中具有重要意义的课题，通过对
超重元素的化学性质进行研究既可以了解它们的物理化学性质是否与现有的元
素周期表变化规律相同，也可以知道相对论效应对超重元素的物理化学性质到底
有多大的影响。本论文主要包括对目前超重元素的液相化学实验研究现状的调研
总结、超重元素Sg 的同族元素Mo 和W 的液相萃取行为研究以及超重元素Rf
的同族元素Zr 和Hf 的阳离子交换行为研究，为进一步开展超重元素Sg 和Rf
的液相化学性质研究提供了坚定的基础