狭缝法合肥光源高亮度注入器发射度测量系统

为了测量受空间电荷效应支配的发射度,合肥光源高亮度注入器采用了狭缝法进行测量,研究了基于狭缝法发射度测量系统的构成,并以实例比较了单狭缝和多狭缝在发射度测量系统中的应用。两种测量方法的结果表明:单狭缝法测量的结果更接近于模拟计算值,可有效避免子束团之间的重叠,适用范围更广。实验结果表明:在240pC电荷量情况下,合肥光源高亮度注入器仍然具有较小的归一化发射度,为(1.84±0.085)mm.mrad。

Electron Acceleration and Bunch Generation by Intense Femtosecond Laser Pulse in Preplasma of a Target

We present analytical studies of electron acceleration in the low-density preplasma of a thin solid target byan intense femtosecond laser pulse.Electrons in the preplasma are trapped and accelerated by the ponderomotive forceas well as the wake field.Two-dimensional particle-in-cell simulations show that when the laser pulse is stopped by thetarget,electrons trapped in the laser pules can be extracted and move forward inertially.The energetic electron bunchin the bubble is unaffected by the reflected pulse and passes through the target with small energy spread and emittance.There is an optimal preplasma density for the generation of the monoenergetic electron bunch if a laser pulse is given.The maximum electron energy is inverse proportion to the preplasma density.

Gas-Phase Deposited Plasmonic Nanoparticles Supported on 3D-Graphene/Nickel Foam for Highly SERS Detection

In this work, we proposed a novel three-dimensional (3D) plasmonic nanostructure based on porous graphene/nickel foam (GNF) and gas-phase deposited Ag nanoparticles (NPs). Ag NPs with high density were directly deposited on the surface of 3D GNF by performing a novel cluster beam deposition approach. In comparison with traditional Ag substrate (SiO2/Ag), such hot-spots enriched 3D nanostructure showed extremely high electromag-netic field enhancement under incident light irradiation which could be used as a sensitive chemical sensor based on surface enhanced Raman scattering (SERS). The experimental results demonstrated that the proposed nanostructure showed superior SERS performance in terms of Raman signal reproducibility and sensitivity for the probe molecules. 3D full-wave simulation showed that the enhanced SERS performance in this 3D hierarchical plasmonic nanostructure was mainly obtained from the hot-spots between Ag NPs and the near-field coupling between Ag NPs and GNF sca olds. This work can provide a novel assembled SERS substrate as a SERS-based chemical sensor in practical applications.

Palladium-Carbon Composite Nanoparticle Films with Enhanced Electrocatalytic Activity for Hydrogen Peroxide Sensors

A nanocomposite electrocatalyst was prepared with the method of cluster beam deposition of palladium nanoparticle thin lms on carbon nanoparticle supporting layers and used as sensitive nonenzyme hydrogen peroxide sensors. An enhancement on the electrocatalytic activity of the palladium nanoparticles toward H2O2 reduction was observed, which was related to the coverage of the carbon nanoparticles. With one monolayer of carbon nanoparticles, the H2O2 detection sensitivity reached the maximum, which was more than twice of that of the pure Pd nanoparticles.

Simulation and Error Analysis of Electro-optic Sampling Measurement of Ultrashort Electron Beam Bunch Length

For the development of high energy physics,it is needed to improve the performance of the relativistic electron bunch.The measurement of the ultrashort relativistic electron pulse becomes one of the key technologies.The electro-optic sampling measurement of relativistic electron pulses is a promising method.This method is nondestructive, non-intrusive,and real-time monitoring.Distance and angles of the reference frames will cause system deviations.In this paper these system deviations are analyzed by simulation.It provides a reference for the experiment.

Catalytic Properties of Pt Cluster-Decorated CeO2 Nanostructures

Uniform clusters of Pt have been deposited on the surface of capping-agent-free CeO2 nanooctahedra and nanorods using electron beam （e-beam） evaporation. The coverage of the Pt nanocluster layer can be controlled by adjusting the e-beam evaporation time. The resulting e-beam evaporated Pt nanocluster layers on the CeO2 surfaces have a clean surface and clean interface between Pt and CeO2. Different growth behaviors of Pt on the two types of CeO2 nanocrystals were observed, with epitaxial growth of Pt on CeO2 nanooctahedra and random growth of Pt on CeO2 nanorods. The structures of the Pt clusters on the two different types of CeO2 nanocrystals have been studied and compared by using them as catalysts for model reactions. The results of hydrogenation reactions clearly showed the clean and similar chemical surface of the Pt clusters in both catalysts. The support- dependent activity of these catalysts was demonstrated by CO oxidation. The Pt/CeO2 nanorods showed much higher activity compared with Pt/CeO2 nanooctahedra because of the higher concentration of oxygen vacancies in the CeO2 nanorods. The structure-dependent selectivity of dehydrogenation reactions indicates that the structures of the Pt on CeO2 nanorods and nanooctahedra are different. Thes differences arise because the metal deposition behaviors are modulated by the strong metal-metal oxide interactions.

High-lying excited states in ^10Be from the ^9Be(^9Be,^10Be)^8Be reaction

A transfer-reaction experiment of ~9Be(~9Be,^(10)Be)~8Be was performed at a beam energy of 45 Me V.Excited states in ^(10)Be up to 18.80 Me V are produced using missing mass and invariant mass methods.Most of the observed high-lying resonant states,reconstructed from theα+~6He and t+~7Li decay channels,agree with the previously reported results.In addition,two new resonances at 15.6 and 18.8 Me V are identified from the present measurement.The 18.55 Me V state is found to decay into both the t + ~7Lig:s: and t + ~7Li?(0.478 MeV) channels, with a relative branching ratio of 0:93 ± 0:33. Further theoretical investigations are encouraged to interpret this new information on cluster structure in neutron-rich light nuclei.