K-600中子发生器辐射防护的改进

目的　对K -60 0中子发生器原有的辐射防护做出评价 ,提出改进措施。方法　使用高灵敏度中子探测器和γ监测器 ,对中子发生器运行时n、γ辐射进行了全面的测量并对辐射场围周的防护设施进行改造。结果　改造前在中子厅西、南屏蔽墙外表面有贯穿辐射 ,特别是中子发生器建筑物项部表面有明显的贯穿辐射 ,并且在距离辐射源 3 0～ 40m处呈现峰值 ,显示出天空反射的效果。改造后辐射场外部周围贯穿辐射大为减弱。结论　通过改进措施达到了降低贯穿辐射的目的

核物质中K���子有效质量

分析了K���子在核物质中有效质量的变化受到核物质标量密度和矢量密度的双重影响,使用Walecka模型和相对论平均场理论,讨论了核物质标量密度与矢量密度的关系,利用这一关系改进了K���子有效质量和核物质密度之间存在的依赖关系。

中子星物质中的K���子凝聚

用密度相关的相对论平均场理论计算了中子星物质中的K���子凝聚 ,结果表明中子星物质发生K���子凝聚的临界密度约为 2 .75 ρ0 .中子星物质URCA过程发生的临界密度在考虑DB核物质中核子自能动量修正时为 ρρ0≈ 3.16,在不考虑DB核物质中核子自能动量修正时为 ρρ0≈ 2 .2 5 ,并进一步计算了密度相关的相对论平均场理论两种参数形式对中子星物质状态方程的影响 .

K-shell ionization cross section of aluminium induced by low-energy highly charged argon ions

Al K-shell X-ray yields are measured with highly charged Arq+ ions (q = 12-16) bombarding against aluminium. The energy range of the Ar ions is from 180 to 380 keV. K-shell ionization cross sections of aluminium are also obtained from the yields data. The experimental data is explained within the framework of 2p pi-2p sigma s rotational coupling. When Ar ions with 2p-shell vacancies are incident on aluminium, the vacancies begin to reduce. Meanwhile, collisions against Al atoms lead to the production of new 2p-shell vacancies of Ar ions. These Ar 2p-shell vacancies will transfer to the 1s orbit of an Al atom via 2p pi-2p sigma s rotational coupling leading to the emission of a K-shell X-ray of aluminiun. A model is constructed based on the base of the above physical scenario. The calculation results of the model are in agreement with the experimental results.

Structural and optical properties of 6H-SiC helium-implanted at 600 K

Single crystals of 6H-SiC were implanted at 600 K with 100 key He ions to three successively fluences and subsequently annealed at different temperatures ranging from 873 to 1473 K in vacuum. The recovery of lattice damage was investigated by different techniques including Rutherford backscattering spectrometry in channeling geometry, Raman spectroscopy and Fourier transform infrared spectroscopy. All three techniques showed that the damage induced by helium ion implantation in the lattice is closely related to the fluence. Rutherford backscattering spectrometry/channeling data on high temperature implantations suggest that for a fluence of 3 x 10(16) He+/cm(2), extended defects are created by thermal annealing to 1473 K. Apart from a well-known intensity decrease of scattering peaks in Raman spectroscopy it was found that the absorbance peak in Fourier transform infrared spectroscopy due to the stretching vibration of Si-C bond shifted to smaller wave numbers with increasing fluence, shifting back to larger wave numbers with increasing annealing temperature. These phenomena are attributed to different lattice damage behavior induced by the hot implantation process, in which simultaneous recovery was prevailing. (C) 2010 Elsevier B.V. All rights reserved.

Measurement of K*(892)(0) and K-0 mesons in Al plus Al collisions at 1.9A GeV

A new measurement of subthreshold K*(892)(0) and K-0 production is presented. The experimental data complete the measurement of strange particles produced in Al + Al collisions at 1.9A GeV measured with the FOPI detector at SIS at GSI (Darmstadt). The K*(892)(0)/K-0 yield ratio is found to be 0.0315 +/- 0.006(stat.) +/- 0.012(syst.) and is in good agreement with the transport model prediction. These measurements provide information on the in-medium cross section of K+-pi(-) fusion, which is the dominant process in subthreshold K*(892)(0) production.

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

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。

Two-quasiparticle K-isomeric states in strongly deformed neutron-rich Nd and Sm isotopes: a projected shell-model analysis

Motivated by recent spectroscopy data from fission experiments, we apply the projected shell model to study systematically the structure of strongly deformed, neutron-rich, even-even Nd and Sm isotopes with neutron number from 94 to 100. We perform calculations for rotational bands up to spin I = 20 and analyze the band structure of low-lying states with quasiparticle excitations, with emphasis given to rotational bands based on various negative-parity two-quasiparticle (2-qp) isomers. Experimentally known isomers in these isotopes are described well. The calculations further predict proton 2-qp bands based on a 5(-) and a 7(-) isomer and neutron 2-qp bands based on a 4(-) and an 8(-) isomer. The properties for the yrast line are discussed, and quantities to test the predictions are suggested for future experiment.

Studies of K-shell x-ray energy shifts induced by MeV/u heavy ions

This paper reports that the K x-ray spectra of the thin target 47Ag, 48Cd, 49In and 50Sn were measured by an HPGe semi-conductor detector in collisions with 84.5 MeV 6C4+ ions. Our experiment revealed the K�� x-ray energy shifts were not obvious and the K��1 x-ray energy shifts were about 90∼110 eV. The simple model of Burch et al has been previously used to calculate the K x-ray energy shifts due to an additional vacancy in 2p orbit. The present work extends the model of Burch to calculate the x-ray energy shifts of multiple ionized atoms induced by heavy ions with kinetic energy of MeV/u. In addition to our experimental results, many other experimental results are compared with the calculated values by using the model.

K���子的有效质量

本论文介绍了国内外对K���子介质效应的研究现状，着重讲述了相对论平均场理论对于高密核物质的研究现状和方法。 同时运用扩展的相对论平均场模型对K���子的有效质量进行了研究，并与其它模型的计算结果作了比较。 在Schaffner相对论平均场模型的框架基础上, 考虑同位旋矢量介子δ, 扩展了强子动力学模型和单玻色子交换K���子模型, 研究了奇异核物质中K���子的有效质量, 发现在奇异核物质中K���子的有效质量随密度的变化比在纯核子物质中的变化小。 同位旋矢量介子δ对在奇异核物质中K���子有效质量随密度变化有明显的影响, 但对不同的参数组, 其影响的大小不同。 由于引入新的δ介子，引起了重子与介子以及δ介子与其他介子的耦合系数的变化，因此我们做了相应的修正

dd→αK+K-反应截面在ANKE/COSY上的测量

ANKE谱仪是位于冷却储存环COSY上的一个内靶实验终端，在它的针对物理目标中，研究靠近 产生阈的共振态a0(980)/f0(980)是一个主要的内容。在通过强相互作用反应对a0/f0进行测量时，初态会选择使用不同的同位旋组合，也就是使用pp、 pn、pd和dd反应。本实验完成于2006年的4、5月间，是一个使用COSY所能提供的最大束流动能Td = 2.273 GeV的dd道反应，它比 产生阈高Q = 39 MeV。在实验中探测了αK+符合事件，结合使用丢失质量分析方法就可以对反应链dd → αf0 → αK+K- 以及其中的f0(980)共振态进行研究。 作为本文的主要内容这个实验，是在Monte - Carlo模拟的帮助下准备后，在4个星期的束流时间里完成的。在实验完成后，数据分析主要集中在对稀有的αK+事件进行鉴别。 ANKE的射程望远镜阵列针对K+介子的鉴别做过优化，在它的帮助下K+就可以通过飞行时间、能量损失方法，以及探测延迟发射的K+衰变产物而被挑选出来。而与之关联的α粒子则是通过它们相对于K+介子的定时点进行鉴别的，α和K+的动量及轨迹由在相应多丝正比室上测量到的径迹信息重建。由此，就可以通过使用丢失质量方法鉴别出实验中没有测量的K-介子。最终所得的αK+丢失质量谱在K-介子质量区域内呈现一个峰，其中包含大约15个事件。由这些αK+K-事件可以得到总的反应截面σtot = (9 ± 3sta ± 5sys) pb。 同位旋破缺反应dd → α(π0η) 的截面由测量得到的σtot (dd → αK+K-)值推出，进而它也给出了在WASA-at-COSY上观察这个过程所要求的最短束流时间。因为这个反应被认为主要是源于通过KK中间态的f0 → a0转化，所以它对于确定出轻标量介子a0(980)/f0(980)的结构扮演着格外重要的角色

Detection of K-ras exon 1 mutations by constant denaturant capillary electrophoresis

Among various mutation detection methods, constant denaturant capillary electrophoresis (CDCE) is one of the most common techniques for rapid identification of known or unknown mutations. In this report, a CDCE analysis method with homemade linear polyacrylamide (LPA) kit was developed on ABI 310 genetic analyzer, the effect and relationship of various denaturing factors in CDCE analysis were investigated and K-ras gene mutations of 31 coloerctal cancer patients were detected. Results indicate that, with the increase of chemical danaturant concentration, the optimum temperature was lowered, and when the concentration of urea (formamide) was higher than 7 M (40%), the homoduplex and heteroduplex of mutant samples were separated with difficulty. Detection results of K-ras gene in colorectal samples indicated that mutations were present in eight (26%) of 31 patients; most mutations were localized in codon 12, which is thought to be a critical step and plays an important role in human colorectal carcinogenesisas. Copyright (C) 2004 John Wiley Sons, Ltd.