基于MCNPX对ADS中子源散裂靶的物理研究

运用蒙卡程序MCNPX对加速器驱动次临界反应堆系统（简称ADS）的标准散裂中子靶进行了计算研究.计算了在0.6～1.5 GeV的质子轰击下,标准Pb靶发生散裂反应产生的中子产额及分布、中子能谱以及靶内能量沉积分布.计算结果与文献理论数据、实验数据进行了比较.     

PGAI瞬发伽玛射线活化成像技术理想化模型的模拟

为了讨论PGAI技术分析的准确性,并验证冷中子和热中子应用于PGAI技术的可行性,通过蒙特卡罗模拟计算软件对PGAI技术理想化模型进行了研究,采用高准直的冷中子及热中子束和高纯锗探测器,对一块5 cm× 5 cm×1 cm均匀铁单质样品进行了模拟计算及图像重建,选取的等效体积大小为1 cm×1 cm×1 cm。结果显示：两种能量中子可以用于PGAI技术实现元素分布测量,但无论使用何种能量中子,由于物料体效应带来的中子自屏效应、中子散射效应以及伽马射线自吸收作用,即便在对均匀单质样品进行测量时,图像重建结果也无法保证各位置元素响应的一致性。因此,在后续工作中,需理清PGAI物理机制,建立相应的修正模型。     

Analysis of Forbush decreases observed using a muon telescope in Antarctica starting on 21 June 2015

A cosmic-ray muon telescope has been collecting data since the end of 2014, which was shortly after the telescope was built in the Zhongshan Station of Antarctica. The telescope is the first observation device to be built by Chinese scientists in Antarctica. The pressure change is very strong in Zhongshan station. The count rate of the pressure correction results shows that the large variations in the count rate are likely caused by pressure fluctuations. During the period from 18 June to 22 June 2015, four halo coronal mass ejections(CMEs) were ejected from the Sun. These CMEs initiated a series of Forbush decreases(FD) when they reached the Earth. We conducted a comprehensive study of the intensity fluctuations of galactic cosmic rays recorded during FDs. The intensity fluctuations used in this study were collected by cosmic ray detectors of multiple stations(Zhongshan, McMurdo,South Polar, and Nagoya), and the solar wind measurements were collected by ACE and WIND. The profile of the FD of 22 June demonstrated a four-step decrease. The traditional one-or two-step FD classification method does not adequately explain the FD profile results. The interaction between the faster CME that occurred on 21 June 2015 and the two slow CMEs of the earlier few days should be considered. The cosmic ray intensities of the South Pole,McMurdo, and Zhongshan stations have similar hourly variations, whereas the galactic cosmic rays recorded between polar and non-polar locations are distinct. The FD pre-increase of 22 June 2015 for the Nagoya muon telescope(non-polar location) lags those of the McMurdo and Zhongshan stations(polar locations) by 1 h. The FD onset of22 June 2015 for the Nagoya muon telescope lags those of the polar locations by 1 h.     

ICF中子发射时间诊断

 对ICF中子发射时间的诊断技术进行了研究,研制了基于快闪烁体和微通道板式光电倍增管的中子发射时间探测器。在某大型激光原型装置上进行了中子发射时间的实验测量,成功获得多发实验的中子发射时间与打靶激光脉冲的时间及中子发射时间之间的关系。实验结果表明：中子发射时间探测器对DT中子和DD中子都能够响应,中子产额测量下限达到10⁷,时间测量不确定度小于20 ps;CH烧蚀层越厚,中子发射时间越长。     

浮栅ROM器件辐射效应机理分析

分析了浮栅ROM器件的辐射效应机理，合理地解释了实验中观察到的现象.指出辐射产生的电子空穴对在器件中形成的氧化物陷阱电荷和界面陷阱电荷是导致存储单元及其外围电路出现错误的原因.浮栅ROM器件的中子、质子和⁶⁰Co γ辐射效应都是总剂量效应 . 关键词： FLASH ROM EEPROM 中子 质子 60Co γ')" href="#">⁶⁰Co γ 总剂量效应     

Langevin study of neutron emission in the reactions ^16O＋^181Ta and ^19F＋^178Hf^＊

The pre-scission neutrons measured in the reactions 16O 181Ta and 19F 178Hf are studied via a Langevin equation coupled with a statistical decay model. We find that because of the mass asymmetry of different entrance channels, the spin distributions of compound nuclei would be different, consequently, the measured neutrons in these two reactions would also different. This means that the entrance channel will affect the particle emission in the fission process of hot nuclei.     

Structure and properties of a novel cobaltate La0.30CoO2

The layered cobaltate La_0.30CoO₂ was prepared from Na_xCoO₂ precursor by a solid-state ionic exchange and was characterized by means of X-ray and neutron diffraction, magnetic, thermal and electric transport measurements. The compound consists of hexagonal sheets of edge-sharing CoO₆ octahedra interleaved by lanthanum monolayers. Compared to Na⁺ in the parent system, the La³⁺ ions occupy only one-third of available sites, forming a 2-dimensional superstructure. The deviation from the ideal stoichiometry La_1/3CoO₂ introduces extra hole carriers into the diamagnetic LS Co³⁺ matrix making the sample Pauli paramagnetic. The temperature dependence of the electrical conductivity in La_0.30CoO₂ follows Mott's T^−1/3 law up to about 400 K, which is in contrast with the standard metallic behavior in the Na⁺ homolog possessing the same formal doping. The experiments are complemented by electronic structure calculations for La_0.30CoO₂ and related Na_xCoO₂ systems.     

Comparison of Electrospray Ionization and Fast Atom Bombardment Mass Spectrometry for the Analysis of Saponins from Alfalfa,Clover, and Mungbeans

The determination of seven saponins in crude plant extracts by electrospray ionization mass spectrometry (ESI-MS) and fast atom bombardment mass spectrometry (FAB-MS) is described. Distinct protonated and natriated (Na-adduct) molecular ions in ESI-MS spectra readily provide molecular weight information, which can be further verified using clusters of molecular ions. Saponin mixtures can be analyzed by ESIMS on varying the potential difference between the capillary and skimmer in the ESI source to decompose impurities. ESI-MS uses less amount of sample than that required by FAB-MS. ESI-MS does not produce structural information, however. The FAB-MS spectra consist mainly of protonated and deprotonated molecular ions with limited structural information. (-)-FAB-MS is more suitable for analyzing saponin samples than the (+)-FAB-MS.     

Catenation and Aggregation of Multi‐Cavity Coordination Cages

A series of metal‐mediated cages, having multiple cavities, was synthesized from Pd^II cations and tris‐ or tetrakis‐monodentate bridging ligands and characterized by NMR spectroscopy, mass spectrometry, and X‐ray methods. The peanut‐shaped [Pd₃L¹₄] cage deriving from the tris‐monodentate ligand L¹ could be quantitatively converted into its interpenetrated [5Cl@Pd₆L¹₈] dimer featuring a linear {[Pd‐Cl‐]₅Pd} stack as an unprecedented structural motif upon addition of chloride anions. Small‐angle neutron scattering (SANS) experiments showed that the cigar‐shaped assembly with a length of 3.7 nm aggregates into mono‐layered discs of 14 nm diameter via solvophobic interactions between the hexyl sidechains. The hepta‐cationic [5Cl@Pd₆L¹₈] cage was found to interact with polyanionic oligonucleotide double‐strands under dissolution of the aggregates in water, rendering the compound class interesting for applications based on non‐covalent DNA binding.