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Acceleration Unit

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Kevin Ronald – One of the best experts on this subject based on the ideXlab platform.

  • Electron beam experiments from a pseudospark discharge
    ITG-Fachbericht, 2004
    Co-Authors: H. Yin, Adrian W. Cross, Alan D R Phelps, W. He, Kevin Ronald

    Abstract:

    A high brightness, low emittance and high current density electron beam is required not only for beam/wave instability experiments but also for accelerators, intense X-ray sources, ion sources and many other specific applications. A series of experiments has been conducted on the beam generation from a pseudospark discharge and its application. The pseudospark produced an electron beam of two phases, an initial 22kV, 50A hollow cathode phase (HCP) beam of brightness 10 9-10 A m -2 rad -2 followed by a 200V, 200A conductive phase (CP) beam of brightness 10 11-12 A m -2 rad -2 . This beam has a higher combined current density and brightness compared to electron beams formed from any other known type of electron source and was used in a Cherenkov maser experiment. Experimental study on the propagation and post-Acceleration of a pseudospark-sourced electron beam from a three-gap pseudospark discharge chamber were also carried out. The aim of these experiments was to post accelerate the lower voltage, higher current CP beam using an Acceleration Unit driven by a 40kV, 125ns voltage pulse produced by a cable Blumlein. The experiments showed that the beam was successfully accelerated from about 200V to more than 40kV. Results from these experiments will be presented.

  • Propagation and post-Acceleration of a pseudospark-sourced electron beam
    Journal of Applied Physics, 2002
    Co-Authors: Adrian W. Cross, Alan D R Phelps, W. He, Kevin Ronald

    Abstract:

    Propagation and post-Acceleration of a pseudospark-sourced electron beam from a three-gap pseudospark discharge chamber were studied in recent experiments. The pseudospark produced an electron beam of two phases, an initial 22 kV, 50 A hollow cathode phase beam of brightness 109−10 Am−2 rad−2 followed by a 200 V, 200 A conductive phase (CP) beam of brightness 1011−12 Am−2 rad−2. The aim of these experiments was to post accelerate the lower-voltage, higher-current CP beam using an Acceleration Unit driven by a 40 kV, 125 ns voltage pulse produced by a cable Blumlein. The experiments were realized by attaching an Acceleration Unit to the downstream side of the anode of the discharge chamber. Both the pseudospark discharge and the cable Blumlein were triggered to ensure time correlation between initiation of the pseudospark discharge and post-Acceleration of the beam.

  • Propagation and post-Acceleration of a pseudospark-sourced electron beam
    Journal of Applied Physics, 2002
    Co-Authors: H. Yin, Adrian W. Cross, Alan D R Phelps, D. Zhu, W. He, Kevin Ronald

    Abstract:

    Propagation and post-Acceleration of a pseudospark-sourced electron beam from a three-gap pseudospark discharge chamber were studied in recent experiments. The pseudospark produced an electron beam of two phases, an initial 22 kV, 50 A hollow cathode phase beam of brightness 10 9-10 Am -2 rad -2 followed by a 200 V, 200 A conductive phase (CP) beam of brightness 10 11-12 Am -2 rad -2 . The aim of these experiments was to post accelerate the lower-voltage, higher-current CP beam using an Acceleration Unit driven by a 40 kV, 125 ns voltage pulse produced by a cable Blumlein. The experiments were realized by attaching an Acceleration Unit to the downstream side of the anode of the discharge chamber. Both the pseudospark discharge and the cable Blumlein were triggered to ensure time correlation between initiation of the pseudospark discharge and post-Acceleration of the beam. © 2002 American Institute of Physics.

Chuhan Zhang – One of the best experts on this subject based on the ideXlab platform.

  • A Coupling Procedure of Finite Element and Scaled Boundary Finite Element Methods for Soil–Structure Interaction in the Time Domain
    Seismic Safety Evaluation of Concrete Dams, 2020
    Co-Authors: Chuhan Zhang

    Abstract:

    A coupling procedure of finite element and scaled boundary finite element (SBFE) methods is presented for three-dimensional dynamic analysis of unbounded soil–structure interaction in the time domain. Based on linear system theory, the Acceleration Unit-impulse response matrix of the unbounded soil calculated by the SBFE method is converted into time-independent matrices; thus, the time history of the Unit-impulse response function of the unbounded medium can be replaced by a state-variable description. Interaction forces between unbounded soil and structure are evaluated by linear equations instead of time-consuming convolution integrals. Since only partial information on the Unit-impulse response function is needed to capture the character of the unbounded medium, and the history of the response function can be truncated, the computational effort spent in the SBFE method can be reduced. The accuracy of the procedure can be controlled with prescribed parameters. Numerical examples of foundation responses agree with previous results and are more efficient than the direct convolution integral method.

  • A coupling procedure of FE and SBFE for soil–structure interaction in the time domain
    International Journal for Numerical Methods in Engineering, 2004
    Co-Authors: Junyi Yann, Chuhan Zhang

    Abstract:

    A coupling procedure of finite element (FE) and scaled boundary finite element (SBFE) is presented for three-dimensional (3D) dynamic analysis of unbounded soil–structure interaction in the time domain. The procedure is implemented with the following efficient techniques: (1) Based on the concepts of linear system theory, the Acceleration Unit-impulse response matrix of the unbounded soil calculated by the SBFE method is converted into a group of time-independent matrices; thus, the time history of the Unit-impulse response function of the unbounded medium can be replaced by an equivalent state-variable description. (2) The interaction forces between the unbounded soil and the structure are evaluated by a system of linear equations instead of time-consuming convolution integrals. (3) Since only the partial information of the Unit-impulse response function is sufficient to capture the main character of the unbounded medium and the history of response function can be truncated at the cut-off time tc, the computational effort spent in the SBFE method can be further reduced. In addition, the accuracy of the procedure can be controlled with prescribed parameters, thus the main advantage of the SBFE method as a highly accurate procedure is retained. Three numerical examples of foundation response demonstrate that good agreement can be achieved when compared with previous results, and high efficiency is also evident compared with the direct convolution integral method. Copyright © 2004 John Wiley & Sons, Ltd.

Chongmin Song – One of the best experts on this subject based on the ideXlab platform.

  • Transient analysis of wave propagation in non-homogeneous elastic unbounded domains by using the scaled boundary finite-element method
    Earthquake Engineering & Structural Dynamics, 2006
    Co-Authors: Mohammad Bazyar, Chongmin Song

    Abstract:

    SUMMARY The scaled boundary finite-element method has been developed for the dynamic analysis of unbounded domains. In this method only the boundary is discretized resulting in a reduction of the spatial dimension by one. Like the finite-element method no fundamental solution is required. This paper extends the scaled boundary finite-element method to simulate the transient response of non-homogeneous unbounded domains with the elasticity modulus and mass density varying as power functions of spatial coordinates. To reduce the number of degrees of freedom and the computational cost, the technique of reduced set of base functions is applied. The scaled boundary finite-element equation for an unbounded domain is reformulated in generalized coordinates. The resulting Acceleration Unit-impulse response matrix is obtained and assembled with the equation of motion of standard finite elements. Numerical examples of non-homogeneous isotropic and transversely isotropic unbounded domains demonstrate the accuracy of the scaled boundary finite-element method. Copyright q 2006 John Wiley & Sons, Ltd.

  • Unit-impulse response matrix of unbounded medium by infinitesimal finite-element cell method
    Computer Methods in Applied Mechanics and Engineering, 1995
    Co-Authors: John P. Wolf, Chongmin Song

    Abstract:

    Abstract To calculate the Unit-impulse response matrix of the unbounded medium, the infinitesimal finite-element cell method based solely on the finite-element formulation and working exclusively in the time domain is developed. A formulation can be derived for Acceleration, velocity and displacement Unit-impulse response matrices. Starting from the Acceleration Unit-impulse impulse response matrix those of the velocity and displacement are constructed. The algorithm to determine the Acceleration Unit-impulse response matrix and its application are simpler than the other two alternatives. As in the cloning algorithm, the approach is based on similarity of the unbounded media corresponding to the interior and exterior boundaries of the infinitesimal finite-element cell. The derivation is performed exclusively in the time domain. At each time station a linear system of equations is solved. The consistent-boundary method to analyse a layered medium in the frequency domain and the viscous-dashpot boundary method are special cases of the infinitesimal finite-element cell method. The error is governed by the finite-element discretization in the circumferential direction, as the width of the finite-element cell in the radial direction is infinitesimal. The infinitesimal finite-element cell method is thus “exact in the finite-element sense”. The method leads to highly accurate results for a vast class of problems, ranging from a one-dimensional spherical cavity to a rectangular foundation embedded in a half-plane.