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Ronald C. Davidson - One of the best experts on this subject based on the ideXlab platform.

  • analytical solutions for the nonlinear longitudinal drift compression expansion of intense charged Particle Beams
    arXiv: Accelerator Physics, 2004
    Co-Authors: Edward A. Startsev, Ronald C. Davidson
    Abstract:

    To achieve high focal spot intensities in heavy ion fusion, the ion beam must be compressed longitudinally by factors of ten to one hundred before it is focused onto the target. The longitudinal compression is achieved by imposing an initial velocity profile tilt on the drifting beam. In this paper, the problem of longitudinal drift compression of intense charged Particle Beams is solved analytically for the two important cases corresponding to a cold beam, and a pressure-dominated beam, using a one-dimensional warm-fluid model describing the longitudinal beam dynamics.

  • Analytical solutions for the nonlinear longitudinal drift compression (expansion) of intense charged Particle Beams
    New Journal of Physics, 2004
    Co-Authors: Edward A. Startsev, Ronald C. Davidson
    Abstract:

    To achieve high focal spot intensities in heavy-ion fusion, the ion beam must be compressed longitudinally by factors of 10--100 before it is focused onto the target. The longitudinal compression is achieved by imposing an initial velocity profile tilt on the drifting beam. In this paper, the problem of longitudinal drift compression of intense charged-Particle Beams is solved analytically for the two important cases corresponding to a cold beam, and a pressure-dominated beam, using a one-dimensional warm-fluid model describing the longitudinal beam dynamics.

  • longitudinal drift compression and pulse shaping for high intensity Particle Beams
    Physical Review Special Topics-accelerators and Beams, 2002
    Co-Authors: Hong Qin, Ronald C. Davidson
    Abstract:

    High beam current can be achieved by longitudinally compressing bunched Beams. The objective of drift compression is to compress a long beam bunch by imposing an initial longitudinal velocity distribution over the length of the beam in the beam frame. The longitudinal dynamics of drift compression and pulse shaping for high intensity Particle Beams are studied using a one-dimensional warm-fluid model. Two self-similar drift compression solutions admitted by the one-dimensional warm-fluid equations are derived. The pulse shaping problem is also solved such that an arbitrary input pulse shape can be shaped into the pulse shapes required by the self-similar drift compression solutions.

  • physics of intense charged Particle Beams in high energy accelerators
    2001
    Co-Authors: Ronald C. Davidson, Hong Qin
    Abstract:

    Theoretical Models of Intense Non-neutral Particle Beams Particle Orbits in Periodic Focusing Field Configurations Nonlinear Kinetic Stability Theorem, Vlasov-Maxwell Description of Periodically-Focused Intense Beam Equilibria Statistically-Averaged Rate Equations Hamiltonian Averaging Techniques Applied to the Nonlinear Vlasov-Maxwell Equations Kinetic Stability Properties and Collective Oscillations in Intense Particle Beams Warm-Fluid Stability Properties and Collective Oscillations in Intense Particle Beams Special Topics on Intense Beam Propagation.

  • physics of intense charged Particle Beams in high energy accelerators
    2001
    Co-Authors: Ronald C. Davidson
    Abstract:

    Theoretical Models of Intense Non-neutral Particle Beams Particle Orbits in Periodic Focusing Field Configurations Nonlinear Kinetic Stability Theorem, Vlasov-Maxwell Description of Periodically-Focused Intense Beam Equilibria Statistically-Averaged Rate Equations Hamiltonian Averaging Techniques Applied to the Nonlinear Vlasov-Maxwell Equations Kinetic Stability Properties and Collective Oscillations in Intense Particle Beams Warm-Fluid Stability Properties and Collective Oscillations in Intense Particle Beams Special Topics on Intense Beam Propagation.

Peter H. Mcmurry - One of the best experts on this subject based on the ideXlab platform.

  • generating Particle Beams of controlled dimensions and divergence i theory of Particle motion in aerodynamic lenses and nozzle expansions
    Aerosol Science and Technology, 1995
    Co-Authors: P Ziemann, David B. Kittelson, Peter H. Mcmurry
    Abstract:

    A Particle beam is produced when a Particle-laden gas expands through a nozzle into a vacuum. This work discusses the theoretical basis of a novel method for producing highly collimated and tightly focused Particle Beams. The approach is to pass the Particle-laden gas through a series of axisymmetric contractions and enlargements (so-called aerodynamic lenses) before the nozzle expansion. Particles are moved closer to the axis by a lens if the Particle sizes are less than a critical value and Particles can be confined very closely to the axis by using multiple lenses in series. Since Particles close to the axis experience small radial drag forces, they stay close to the axis during nozzle expansion and therefore form a narrow Particle beam downstream. The major effects that limit the minimum beam width are Brownian motion and lift forces on Particles during the nozzle expansion. Simple theoretical models are developed in this work to estimate the minimum Particle beam width set by these effects. While the...

  • generating Particle Beams of controlled dimensions and divergence ii experimental evaluation of Particle motion in aerodynamic lenses and nozzle expansions
    Aerosol Science and Technology, 1995
    Co-Authors: P Ziemann, David B. Kittelson, Peter H. Mcmurry
    Abstract:

    A Particle-beam-forming apparatus for producing narrow Particle Beams was developed based on the theory discussed in paper I of this series. It consists of a variable number of aerodynamic lenses (short capillaries and/or thin-plate orifices with diameters ranging from 3.5 to 7.0 mm) followed by an accelerating nozzle (3 mm). It was evaluated using monodisperse DOS and NaCl Particles (0.02–0.24 μm) at upstream pressures on the order of 1 torr. The Particle Beams produced by the lens-nozzle system were focused through a skimmer (1 mm) into a high vacuum chamber (10−4–10−5 torr) where the beam widths, velocities and transport efficiencies were measured. The experiments showed that as more lenses were added the Particle beam widths were reduced asymptotically to the minimum values. For spherical Particles (DOS) these minimum values are in good agreement with the Brownian limit derived in paper I. For nonspherical Particles (NaCl) these minimum widths are much larger than the Brownian limit, indicating that b...

F Zonca - One of the best experts on this subject based on the ideXlab platform.

  • fast excitation of geodesic acoustic mode by energetic Particle Beams
    Physics of Plasmas, 2015
    Co-Authors: Jintao Cao, F Zonca, Zhiyong Qiu
    Abstract:

    A new mechanism for geodesic acoustic mode (GAM) excitation by a not fully slowed down energetic Particle (EP) beam is analyzed to explain experimental observations in Large Helical Device. It is shown that the positive velocity space gradient near the lower-energy end of the EP distribution function can strongly drive the GAM unstable. The new features of this EP-induced GAM (EGAM) are: (1) no instability threshold in the pitch angle; (2) the EGAM frequency can be higher than the local GAM frequency; and (3) the instability growth rate is much larger than that driven by a fully slowed down EP beam.

  • fast excitation of geodesic acoustic mode by energetic Particle Beams
    arXiv: Plasma Physics, 2015
    Co-Authors: Jintao Cao, F Zonca, Zhiyong Qiu
    Abstract:

    A new mechanism for Geodesic acoustic mode (GAM) excitation by a not fully slowed down energetic Particle (EP) beam is analysed to explain experimental observations in Large Helical Device. It is shown that the positive velocity space gradient near the lower-energy end of the EP distribution function can strongly drive GAM unstable. The new features of this EP-induced GAM (EGAM) are: 1. no instability threshold in the pitch angle; 2. the EGAM frequency can be higher than the local GAM frequency; and 3. the instability growth rate is much larger than that driven by a fully slowed down EP beam.

Edward A. Startsev - One of the best experts on this subject based on the ideXlab platform.

Eike Rietzel - One of the best experts on this subject based on the ideXlab platform.

  • gated irradiation with scanned Particle Beams
    International Journal of Radiation Oncology Biology Physics, 2009
    Co-Authors: Christoph Bert, Alexander Gemmel, Nami Saito, Eike Rietzel
    Abstract:

    Purpose To demonstrate mitigation of the interplay effects of scanned Particle Beams and residual target motion within a gating window by increased overlap of pencil Beams. Methods and Materials Lateral overlap was increased by increasing the pencil beam widths or by decreasing the distance between the pencil Beams (scan grid). Longitudinal overlap was increased by reducing the distance between iso-range slices. For scanned carbon ion Beams, simulation studies were performed and validated experimentally to determine the required parameters for different residual motion characteristics. The dose distributions were characterized by the maximal local deviations representing local over- and underdosage. Results For residual lateral motion, the local deviations were Conclusion In charged Particle therapy with a scanned beam, interplay effects between gated beam delivery and residual target motion can be decreased effectively by increasing the overlap between pencil Beams laterally, as well as longitudinally.

  • quantification of interplay effects of scanned Particle Beams and moving targets
    Physics in Medicine and Biology, 2008
    Co-Authors: Christoph Bert, Sven Oliver Grozinger, Eike Rietzel
    Abstract:

    Scanned Particle Beams and target motion interfere. This interplay leads to deterioration of the dose distribution. Experiments and a treatment planning study were performed to investigate interplay. Experiments were performed with moving radiographic films for different motion parameters. Resulting dose distributions were analyzed for homogeneity and dose coverage. The treatment planning study was based on the time-resolved computed tomography (4DCT) data of five lung tumor patients. Treatment plans with margins to account for respiratory motion were optimized, and resulting dose distributions for 108 different motion parameters for each patient were calculated. Data analysis for a single fraction was based on dose-volume histograms and the volume covered with 95% of the planned dose. Interplay deteriorated dose conformity and homogeneity (1-standard deviation/mean) in the experiments as well as in the treatment-planning study. The homogeneity on radiographic films was below approximately 80% for motion amplitudes of approximately 15 mm. For the treatment-planning study based on patient data, the target volume receiving at least 95% of the prescribed dose was on average (standard deviation) 71.0% (14.2%). Interplay of scanned Particle Beams and moving targets has severe impact on the resulting dose distributions. Fractionated treatment delivery potentially mitigates at least parts of these interplay effects. However, especially for small fraction numbers, e.g. hypo-fractionation, treatment of moving targets with scanned Particle Beams requires motion mitigation techniques such as rescanning, gating, or tracking.

  • online compensation for target motion with scanned Particle Beams simulation environment
    Physics in Medicine and Biology, 2004
    Co-Authors: Eike Rietzel, Thomas Haberer, Qiang Li, Sven Oliver Groezinger, G Kraft
    Abstract:

    Target motion is one of the major limitations of each high precision radiation therapy. Using advanced active beam delivery techniques, such as the magnetic raster scanning system for Particle irradiation, the interplay between time-dependent beam and target position heavily distorts the applied dose distribution. This paper presents a simulation environment in which the time-dependent effect of target motion on heavy-ion irradiation can be calculated with dynamically scanned ion Beams. In an extension of the existing treatment planning software for ion irradiation of static targets (TRiP) at GSI, the expected dose distribution is calculated as the sum of several sub-distributions for single target motion states. To investigate active compensation for target motion by adapting the position of the therapeutic beam during irradiation, the planned beam positions can be altered during the calculation. Applying realistic parameters to the planned motion-compensation methods at GSI, the effect of target motion on the expected dose uniformity can be simulated for different target configurations and motion conditions. For the dynamic dose calculation, experimentally measured profiles of the beam extraction in time were used. Initial simulations show the feasibility and consistency of an active motion compensation with the magnetic scanning system and reveal some strategies to improve the dose homogeneity inside the moving target. The simulation environment presented here provides an effective means for evaluating the dose distribution for a moving target volume with and without motion compensation. It contributes a substantial basis for the experimental research on the irradiation of moving target volumes with scanned ion Beams at GSI which will be presented in upcoming papers.