Results 1 - 10 of 332
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[en] In applying mode expansion to solve the CSR impedance for a section of toroidal vacuum chamber with rectangular cross section, we identify the eigenvalue problem for the radial eigenmodes which is different from that for cylindrical structures. In this paper, we present the general expressions of the radial eigenmodes, and discuss the properties of the eigenvalues on the basis of the Sturm-Liouville theory.
[en] In this paper, we discuss in a coherent manner variousapplications of the cancellation effect, such as a coastingbeam, a short bunch in steady-state interacting with off-orbit particles, transient self-interaction of a short bunch entering to acircular orbit from straightpath, and a converging beam in a bunch compression chicane.
[en] Feedthrough of interference from the AC power line into accelerator components is a problem which in pulsed accelerators can be reduced by operation synchronous with the AC line. This means of avoiding line-frequency effects is ineffective for continuous wave machines such as the CEBAF accelerator. We have measured line-frequency perturbations at CEBAF both in beam position and energy by using the beam position monitor system as a multiple-channel sampling oscilloscope. Comparing these data against the measured static optics (taken synchronously with the AC line) we have been able to identify point sources of interference, and resolve line-synchronous variations in the beam energy at a level near 0.001%. 3 refs., 2 figs., 1 tab
[en] Hadronic production of charmonium states such as J/ψ, χc, and ψ' provides valuable tests for the theory of strong interaction, known as Quantum Chromodynamics (QCD), and for related theoretical models. In this thesis the authors analyze data collected by the experiment E672/E706 using 530 GeV/c π- beam incident on Be and Cu targets at Tevatron II, Fermi National Accelerator Laboratory. The experiment was performed at the highest πN center-of-mass energy up to date and very respectable charmonium mass resolution was achieved. The apparatus of the experiment for the 1990 run-period is described. J/ψ mesons are detected in the μ+μ- decay mode. The integrated and differential cross sections of J/ψ hadronic production are measured. The dependence of the cross section on atomic numbers of the targets and on reaction inelasticity are also determined. The χc mesons are detected in the decay mode χc → J/ψγ, with the photon converted to e+e- in the spectrometer. The mass resolution is sufficient to resolve χc1(3508) and χc2(3555). The ψ' mesons are detected in both J/ψπ+π- and μ+μ- decay modes. The fractions of observed J/ψ coming from χc or ψ' decays are measured. From these results, the prompt production cross sections of the charmonium states J/ψ, χc, and ψ' are estimated
[en] When an electron bunch with initial linear energy chirp traverses a bunch compression chicane, the bunch interacts with itself via coherent synchrotron radiation (CSR) and space charge force. The effective longitudinal CSR force for such kind of 2D bunch on a circular orbit has been analyzed earlier (1). In this paper, we present the analytical results of the effective longitudinal CSR force for a 2D energy-chirped bunch going through a general orbit, which includes the entrance and exit of a circular orbit. In particular, we will show the behavior of the force in the last bend of a chicane when the bunch is under extreme compression. This is the condition when bifurcation of bunch phase space occurs in many CSR measurements. (1) R. Li, Phys. Rev. ST Accel. Beams 11, 024401 (2008)
[en] When the JLAB FEL is under CW operation, it had been observed that temperature rises over the wiggler vacuum chamber, presumably as the result of the power deposition on the resistive wall of the wiggler chamber. Previous analyses have been done on the resistive wall impedance for various cases, such as DC, AC, and anomalous skin effects*. Here we report an investigation on the beam kinetic energy losses for each of these cases. This study includes the non-ultrarelativistic effect on resistive wall loss, for both round pipe and parallel plates. We will present the comparison of our results with the measured data obtained during CW operation of the JLAB FEL. Other possible factors contributing to the measured heating will also be discussed
[en] A financial price model is developed based on the voter interacting system in this work. The Lempel–Ziv complexity is introduced to analyze the complex behaviors of the stock market. Some stock market stylized facts including fat tails, absence of autocorrelation and volatility clustering are investigated for the proposed price model firstly. Then the complexity of fluctuation behaviors of the real stock markets and the proposed price model are mainly explored by Lempel–Ziv complexity (LZC) analysis and multi-scale weighted-permutation entropy (MWPE) analysis. A series of LZC analyses of the returns and the absolute returns of daily closing prices and moving average prices are performed. Moreover, the complexity of the returns, the absolute returns and their corresponding intrinsic mode functions (IMFs) derived from the empirical mode decomposition (EMD) with MWPE is also investigated. The numerical empirical study shows similar statistical and complex behaviors between the proposed price model and the real stock markets, which exhibits that the proposed model is feasible to some extent. - Highlights: • A financial price dynamical model is developed based on the voter interacting system. • Lempel–Ziv complexity is the firstly applied to investigate the stock market dynamics system. • MWPE is employed to explore the complexity fluctuation behaviors of the stock market. • Empirical results show the feasibility of the proposed financial model.
[en] We propose a method here which allows the measurement of the cavity resonance frequency in a frequency range up to ±5 kHz from the operating frequency. This is achieved by phase modulation of the incident signal with noise to drive the cavity with a broad band spectrum. The cavity resonance frequency can then be determined from the response signal of the field probe, which has a narrow frequency spectrum due to the high loaded Q of the cavity of 6.6x106, corresponding to a cavity bandwidth of 125 Hz
[en] Electrochemical studies were carried out on the La0.7Mg0.3Ni3.4-xMn0.1Cox (x=0.00, 0.30, 0.60, 0.75, 0.90, 1.05, 1.15, 1.30, 1.45, 1.60) hydrogen storage alloys. Firstly, it was found that partial substitution of Ni by Co could improve effectively the cyclic stability of the La-Mg-Ni-Mn-Co system hydrogen storage alloys with little loss of the maximum discharge capacity, which can be ascribed to a relative lower cell volume change during hydriding/dehydriding cycling and an increase in the surface passivation. Secondly, the high rate dischargeability (HRD) measurement shows that the electrochemical kinetics of the alloy electrodes first increases owing to the concentrations of Co and Ni on the surface of the alloy particles and the subsequent formation of the Raney Ni-Co film with higher electrocatalytic activity after moderate Co substitution for Ni, and then decreases with the increase in Co content because of the reduction of surface electrocatalytic activity due to the diminution of the effective surface area and the increase of the attractive interaction between absorbed hydrogen atoms. Thirdly, the electrochemical impedance spectroscopy (EIS), linear polarization, anodic polarization, potential step, and cyclic voltammetry measurements also confirm the change of the electrochemical kinetics of these type of alloy electrodes. Above all, the optimal content of Co in La0.7Mg0.3Ni3.4-xMn0.1Cox alloys for negative electrodes in alkaline rechargeable secondary batteries lies in the range 0.75≤x≤1.15
[en] In this paper, the structural, hydrogen storage and electrochemical studies were performed on the La0.7Mg0.3Ni3.4-xMn0.1Cox (x=0.00, 0.30, 0.60, 0.75, 0.90, 1.05, 1.15, 1.30, 1.45, 1.60) hydrogen storage alloys. The phase structures were identified by X-ray diffraction (XRD) and Rietveld analyses showing that all alloys consist mainly of two phases: the (La,Mg)Ni3 phase with the rhombohedral PuNi3-type structure and the LaNi5 phase with the hexagonal CaCu5-type structure besides a small amount of LaNi phase. Both a and c parameters of the (La,Mg)Ni3 phase and the LaNi5 phase increase with increasing Co content and a subsequent expansion of the cell volumes owing to the atomic radius of Co (1.67 Angst) being somewhat larger than that of Ni (1.62 Angst). Moreover, the abundances of the (La,Mg)Ni3 phase and the LaNi5 phase are changed relatively. P-C isotherms indicate that the equilibrium pressure for absorption/desorption hydrogen depresses steadily due to the expansion of the cell volume and the hydrogen storage capacity first increases and then decreases with increasing x from 0.00 to 1.60. Moreover, the absorption/desorption pressure hysteresis decreases and the plateau slope increases with the increase in Co content