Single-bunch emittance dilution in the perfect ILC main linac

In the ILC (International Linear Collider) main linac, low emittance preservation is the most important issue for beam dynamics study. As the main sources of emittance dilution, the dispersive and wakefield effects were studied in this paper. The theoretical calculations and numerical simulations of these two effects on single-bunch emittance dilution, without any misalignment errors, are presented in detail.     

Neutrino masses and lepton-flavor-violating τ decays in the supersymmetric left-right model

In the supersymmetric left-right model, the light neutrino masses are given by the Type-Ⅱ seesaw mechanism. A duality property of this mechanism indicates that there exist eight possible Higgs triplet Yukawa couplings which result in the same neutrino mass matrix. In this paper, we work out the one-loop renormalization group equations for the effective neutrino mass matrix in the supersymmetric left-right model. The stability of the Type-Ⅱ seesaw scenario is briefly discussed. We also study the lepton-flavor-violating processes (τ→ μγ and τ→eγ) by using the reconstructed Higgs triplet Yukawa couplings.     

On the detectability of Galactic dark matter annihilation into monochromatic gamma-rays

Monochromatic γ-rays are thought to be the smoking gun signal for identifying dark matter annihilation. However, the flux of monochromatic γ-rays is usually suppressed by virtual quantum effects since dark matter should be neutral and does not couple with γ-rays directly. In this work, we study the detection strategy of the monochromatic γ-rays in a future space-based detector. The flux of monochromatic γ-rays between 50 GeV and several TeV is calculated by assuming the supersymmetric neutralino as a typical dark matter candidate. The detection both by focusing on the Galactic center and in a scan mode that detects γ-rays from the whole Galactic halo are compared. The detector performance for the purpose of monochromatic γ-ray detection, with different energy and angular resolution, field of view, and background rejection efficiencies, is carefully studied with both analytical and fast Monte-Carlo methods.     

Prompt neutron multiplicity distribution for ~（235）U（n,f） at incident energies up to 20 MeV

For the n+²³⁵U fission reaction, the total excitation energy partition of the fission fragments, the average neutron kinetic energy <ε>(A) and the total average energies E_γ(A) removed by γ rays as a function of fission fragment mass are given at incident energies up to 20 MeV. The prompt neutron multiplicity as a function of the fragment mass, ν(A), for neutron-induced fission of ²³⁵U at different incident neutron energies is calculated. The calculated results are checked with the total average prompt neutron multiplicities ν and compared with the experimental and evaluated data. Some prompt neutron and γ emission mechanisms are discussed.     

Application of the parametric for mulae for electromagnetic showers in unconverted γ/π~0 discrimination

In the LHC experiment, the neutral pions produced during jet fragmentation are the background sources for all physics channels with high-energy photons in their final state. In this paper, the application of the three-dimensional parametric formula for electromagnetic (EM) showers, which we developed in the Alpha Magnetic Spectrometer II experiment, is presented to distinguish the unconverted photons from the neutral pions. With the constructed electromagnetic calorimeter (ECAL) in a GEANT4 simulation, the parametric formulae were validated and the unconverted γπ⁰ discrimination was performed with the Toolkit for Multivariate Data Analysis (TMVA) package in ROOT for different transverse energies ranging from 15 GeV to 75 GeV, which is the most sensitive region for light Higgs (with mass ～120 GeV) searches with the channel H→γγ. With this discrimination method and the selected transverse energy region, we can reject π⁰ with the efficiency from ～40% (65--75 GeV) to ～90% (15--25 GeV) when keeping 90% γ efficiency.     

Enhanced high temperature cycling performance of LiMn2O4/graphite cells with methylene methanedisulfonate（MMDS） as electrolyte additive and its acting mechanism

The effects of methylene methanedisulfonate(MMDS) on the high-temperature(~50℃) cycle performance of LiMn_2O_4/graphite cells are investigated.By addition of 2 wt%MMDS into a routine electrolyte,the high-temperature cycling performance of LiMn204/graphite cells can be significantly improved.The analysis of differential capacity curves and energy-dispersive X-ray spectrometry(EDX) indicates that MMDS decomposed on both cathode and anode.The three-electrode system of pouch cell is used to reveal the capacity loss mechanism in the cells.It is shown that the capacity fading of cells without MMDS in the electrolytes is due to irreversible lithium consumption during cycling and irreversible damage of LiMn_2O_4 material,while the capacity fading of cell with 2 wt%MMDS in electrolytes mainly originated from irreversible lithium consumption during cycling.     

利用同步辐射进行X射线激发光学发光研究

本文介绍利用北京正负电子对撞机产生的同步辐射X光进行激发晶体(GGG:Nd~(3+),LaF_3:Nd~(3+))的光学发光研究的有关实验技术和设备。     

电子注在等离子体中的运动及传输特性

 从填充等离子体微波管漂移空间电子运动轨迹方程出发, 详细阐述了A区和B区电子注的聚束性能, 电子围绕平衡半径在A区和B区交替波浪式前进, 波纹的周期和幅度与等离子体密度和电子运动速度有关, 此外, 对弱加速场电子传输性能的研究表明, 调节等离子体参数、电压和场强, 可实现电子注无磁场聚束传输。     

线极化摇摆场中的束流动力学

对线极化摇摆场中,在有引导磁场或四极磁场时的电子轨迹特性、束流包络特性进行了解析分析和数值分析,推得了线极化摇摆场中的梯度漂移解析表达式,借助于Bogoliubov的非线性渐近法和奇异摄动法得到的解析分析结果与数值分析结果很好地吻合。     

利用针缝法测量强流栅控脉冲电子枪束流发射度

采用单缝单针法测量电子枪束流的发射度。用可移动的宽0.1mm单缝取样,与缝平行的直径为0.1mm匀速运动的探针接收穿过狭缝的束流。 缝、针距离为59mm,角分辨率为3.4mrad,系统最大接收度为0.64cm·rad。缝、针间设有平行度调节装置,提高了测量精度;狭缝板设有水冷结构,可承受较大的束流功率,采用良好的屏蔽及合理的二次电子抑制结构,清晰地测出了10~(-10)A量级的弱信号电流。所测相图的相对误差约为8％。利用该装置方便地测得了电子枪高压、栅控脉冲电压、阴极温度、脉冲流强等不同条件下的发射度变化。