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报道了在新建成的放射性次级束流线上完成的20Na的β+缓发α粒子发射20Na—→β+ 20Ne→16O+α的在束测量.通过飞行时间和能损符合的方法实现20Na次级束流的在束鉴别与调制.在束和停束两个获取时段分别完成对次级束流和β+缓发粒子的记录.利用脉冲发生器和记数器实现20Na缓发粒子衰变半衰期的测量.实验测量到20Ne几个低能共振能级的衰变能量分别为2.69,3.09,4.74,5.54MeV,相对强度分别为100,4.15,1.10,15.20.测量到20Na的β+缓发α衰变的半衰期为(459±7)ms,与现有的核数据基本上吻合. 相似文献
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BEPCⅡ是BEPC的升级工程, 它被设计工作在亮度为1×1033cm-2.s-1的τ-charm能区. 根据用几个不同的程序进行的束--束相互作用的模拟结果, BEPCⅡ的亮度较设计亮度有不同程度的下降. 其中一个程序的计算结果表明, 在原设计对撞模式下运行, BEPCⅡ的运行亮度只能达到0.50×1033cm-2.s-1. 为了提高BEPCⅡ的运行亮度, 研究了小动量压缩因子的对撞模式, 亮度可以提高到0.54×1033cm-2.s-1. 相应的束长由1.5cm减小到1.2cm. 为了和1.2cm的束长相匹配, 又研究了对撞点垂直β函数等于1.2cm的对撞模式. 根据束--束相互作用的模拟结果, 选择了几个高亮度的工作点, 对它们的线性lattice和动力学孔径等进行了研究和优化. 其中, 最高的亮度可以达到0.828×1033cm-2.s-1. 相似文献
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蔡晓红 邵曹杰 卢荣春 李明生 阮芳芳 詹文龙 Yu.V.Shestakov D.K.Torpokov R.S.Sadykov S.A.Zevakov 《中国物理 C》2007,31(8):750-754
为HIRFL-CSR团簇内靶设计加工了新的供气系统, 拆换了原有的喷嘴, 对氢气和氩气进行了新的实验, 获得了氢气和氩气的稳定团簇束, 解决了困扰团簇靶稳定运行的喷嘴堵塞问题. 获得的氢团簇束密度为1.75×1013 atoms/cm3, 好于德国GSI内靶对氢束所达到的1×1013atoms/cm3. 研究了团簇束的衰减, 测量了氢束和氩束的有效靶厚, 研究了团簇靶系统对这两种工作气体的长期运行稳定性. 对氢和氩两种工作气体, 各级气压呈现了良好的稳定性, 说明在实验的时间范围内, 团簇靶运行稳定. 相似文献
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用程函近似分析在高能核碰撞中次级作用对K+/π+比的影响.计算表明,在K+/π+比中次级碰撞效应是重要的. 相似文献
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用R.Madey等人提出的由核反应参数计算屏蔽的方法,计算了入射离子单核能为0.6、1.2GeV12C束轰击厚Cu靶的次级中子屏蔽.当入射离子束流为1×1013ions/s时,其前向和侧向混凝土屏蔽厚度分别为9.8、4.8m(对0.6GeV)和11.5、6.9m(对1.2GeV). 相似文献
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高能重离子碰撞中K+/π+比例的显著升高被认为是夸克、胶子等离子体形成的一个可能信号.基于参加者核子模型和次级粒子形成时间的概念,本文对Si(14.5A GeV/c)与Au的中心碰撞进行了Monte Carlo模拟计算.在计算中考虑了如下次级碰撞过程:πN→K+Y、ππ→KK以及πN的单电荷交换反应.本文的计算结果表明:由这些次级碰撞过程导致的末态的K+/π+比例的升高不足以解释BNL的E802组观测到的实验数据. 相似文献
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π介子与周围核子发生次级碰撞可以改变K+/π+比.本文用Glauber模型计算在质子-核和核-核碰撞中的K+/π+比.计算表明,末态相互作用对K+/π+比的效应是重要的. 相似文献
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在散裂中子源注入系统工作过程中,剥离膜是实现负氢离子转换为质子注入加速的关键部件。百nm到μm级厚度的剥离膜超薄易碎,安装及系统真空获得难度较高,一直是散裂中子源研究的重点。对比了国外膜片固定方式现状,通过设计剥离膜辅助安装装置,实现剥离膜样品批量安装;通过Fluent仿真分析,模拟得出膜片在不同进出口压差下真空获得过程中的压力分布、膜片附件空气扰动及系统空气流动,制定在不破坏剥离膜的前提下真空获得方案,并获得剥离膜系统超高真空环境。 相似文献
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K. Saito 《辐射效应与固体损伤》2013,168(1-4):29-41
Transformation behaviour in thin foils of a Ni-12 at.% Ti alloy was investigated by means of in situ aging and electron irradiation experiments inside a high voltage electron microscope. It is shown experimentally that the mode or the morphology of precipitation and ordering reactions in the thin foils differ somewhat from that observed in the bulk material. In the thicker part of the thin foils aged in situ at 873–973 K, a periodic modulated structure is observed to consist of a periodic array of cuboidal coherent particles along the [100] crystallographic directions. The development of ordering within the solute enriched particles appears to be much slower than in the bulk specimen In the thinner part of the foil or in the near-surface regions, no precipitation or ordering occurs and so-called precipitate-free zones (PFZs) are observed. At a higher temperature of 1073 K, precipitation takes place preferentially at the foil surfaces Electron irradiation at elevated temperatures is found to disturb the formation and growth of a metastable modulated structure. and alter the distribution and the morphology of precipitate particles initially present. The observed transformation characteristics in the thin foil can be understood in terms of the proximity of external surfaces which act as dominant sinks for point defects or solute atoms in a thin foil. Electron irradiation affects the sink efficiency of the foil surfaces as a result of the radiation-enhanced diffusion. 相似文献
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The ability of a single-channel time reversal acoustic systems to focus and receive ultrasound radiation is considered. The
basic element of these systems is a liquid-filled acoustic reverberator. Two types of the reverberators have been experimentally
studied; one of them is a thin-wall cylindrical balloon used in ultrasound catheters for treatment of cardiac fibrillation,
and the other consists of plane-parallel foil layers. It is demonstrated that such systems can effectively focus ultrasound
using only one radiation channel. Random deformation of balloon walls and foil layers leads to a noticeable improvement of
focusing quality and helps to overcome the limitations imposed by a spatial symmetry of a system. The use of a binary radiation
mode increases the focal field intensity as compared to the conventional mode. The possibility of spatial localization of
external sources with the use of the time reversal focusing system as a receiver is demonstrated. 相似文献
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Hongbo Li C. H. M. van der Werf A. Borreman J. K. Rath Ruud E. I. Schropp 《固体物理学:研究快报》2008,2(4):157-159
In this letter we report the result of an a‐Si:H/nc‐Si:H tandem thin film silicon solar mini‐module fabricated on plastic foil containing intrinsic silicon layers made by hot‐wire CVD (efficiency 7.4%, monolithically series‐connected, aperture area 25 cm2). We used the Helianthos cell transfer process. The cells were first deposited on a temporary aluminum foil carrier, which allows the use of the optimal processing temperatures, and then transferred to a plastic foil. This letter reports the characteristics of the flexible solar cells obtained in this manner, and compares the results with those obtained on reference glass substrates. The research focus for implementation of the hot‐wire CVD technique for the roll‐to‐roll process is also discussed. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
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Shvetsov G.A. Bashkatov Y.L. Anisimov A.G. Stadnichenko I.A. 《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》1989,17(3):365-370
Results of the optical diagnostics of the plasma armature in railgun macroparticle accelerators are summarized. Determining the structure of the plasma armature and measuring its brightness and temperature at an initial stage of high-current discharge are the focus of attention. Experiments show that the plasma induced by the electric explosion of a copper foil undergoes complex variations that include plasma stratification. The plasma structure continuously changes, being of a complicated, irregular character. The lifetime of an individual stratum changes within 1 to 10 μs. In experiments on solid-body acceleration, the arc burns for a long time at the foil site, where a strong electrode erosion takes place. As the body passes through the railgun channel, the plasma armature continuously increases its length so that it gradually occupies the entire accelerator channel. the current is observed to redistribute itself from the front towards the end face of the plasma armature. The maximum brightness temperature measured in the experiments is 26000±2600 K. As is shown by the experiments, it is arguable that a magnetic-compressed discharge may be realized in a railgun solid-body accelerator with a plasma armature 相似文献
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Da Silva L.B. Cauble R. Barbee T.W. Jr. Celliers P. Ciarlo D. Libby S. London R.A. Matthews D. Mrowka S. Moreno J.C. Ress D. Trebes J.E. Wan A.S. Weber F. 《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》1996,24(1):31-32
We have developed a soft X-ray interferometer capable of probing large high-density plasmas with micron spatial resolutions. A neon-like yttrium X-ray laser operating at 155 Å was combined with the Mach-Zehnder interferometer to obtain electron density profiles of a laser-produced exploding selenium foil plasma. The plasma was produced with one Nova laser beam using a 120-μm line focus, the same conditions used to create a selenium X-ray laser. The interferogram of the selenium plasma was obtained from an end-on perspective 相似文献
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McKenna P Carroll DC Clarke RJ Evans RG Ledingham KW Lindau F Lundh O McCanny T Neely D Robinson AP Robson L Simpson PT Wahlström CG Zepf M 《Physical review letters》2007,98(14):145001
An experimental investigation of lateral electron transport in thin metallic foil targets irradiated by ultraintense (>or=10(19) W/cm2) laser pulses is reported. Two-dimensional spatially resolved ion emission measurements are used to quantify electric-field generation resulting from electron transport. The measurement of large electric fields ( approximately 0.1 TV/m) millimeters from the laser focus reveals that lateral energy transport continues long after the laser pulse has decayed. Numerical simulations confirm a very strong enhancement of electron density and electric field at the edges of the target. 相似文献
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T. Boehly B. Yaakobi D. Shvarts D. Meyerhofer P. Audebert J. Wang M. Russotto B. Boswell R. Epstein R. S. Craxton J. M. Soures 《Applied physics. B, Lasers and optics》1990,50(3):165-172
New target geometries for collisional excitation X-ray laser experiments (in nickel) were proposed, analyzed, and experimentally studied on the Glass Development Laser (GDL). Experiments using a short line focus lens with new target geometries showed general agreement with predictions. The new geometries are designed to yield a higher gain and reduced refraction due to: (1) a higher plasma density, (2) a wider lateral density profile, and (3) a concave lateral density profile. These new geometries were: (1) two parallel exploding (thin) foils, irradiated from one side only, (2) two ablating (thick) foils, one of which is irradiated on its inner face, and (3) an exploding foil in front of an ablating foil, irradiated by a single laser beam incident on the thin foil. New experiments with a long line focus are in progress. The intensity ratio of Ne-like and F-like Ni lines is used to deduce the temperature, and these results together with the absolute intensity, yield the density profile. The results show improvement achieved with the new target geometries: the density is higher (leading to a higher gain), and the concave density profile results in collimation rather than divergence of the X-ray laser beam. Theoretical developments included: (1) prediction of high gain on new type transitions in neon like ions involving the excitation of an inner (2s) electron, and (2) development of a ray tracing code for an amplifying medium of varying (e.g., collimating) lateral density profile. Results using this code are shown for concave lateral density profiles. 相似文献