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Research Interests: Mechanical Engineering, Physics, Materials Science, Optics, Laser, and 15 moreRisk, Medicine, Lasers, Applied, Optical Amplifiers, Sapphire, Applied Optics, Optical physics, Femtosecond, Optics and Photonics, Aluminum oxide, Amplifier, Equipment Design, Electrical And Electronic Engineering, and Laser Amplifiers
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The results of Monte Carlo calculated dose distributions of proton treatment of ocular melanoma are presented. An efficient spot scanning method utilizing active energy modulation, which also minimizes the number of target spots was... more
The results of Monte Carlo calculated dose distributions of proton treatment of ocular melanoma are presented. An efficient spot scanning method utilizing active energy modulation, which also minimizes the number of target spots was developed. We simulated various parameter values for the particle energy spread and the pencil beam diameter in order to determine values suitable for medical treatment. We found that a 2.5-mm-diameter proton beam with a 5% Gaussian energy spread was suitable for treatment of ocular melanoma while preserving vision for the typical case that we simulated. The energy spectra and the required proton current were also calculated and are reported. The results are intended to serve as a guideline for a new class of low-cost, compact accelerators.
Research Interests: Materials Science, Optics, Monte Carlo Simulation, Monte Carlo, Medicine, and 14 moreHumans, Lasers, Laser Driven Ion Acceleration, Melanoma, Activation Energy, Proton Therapy, Ocular Melanoma, Proton, Protons, Monte Carlo Method, Radiological Physics and Technology, Medical Treatment, Pencil beam scanning, and Energy Spectra
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Research Interests: Physics, Optics, Radiation, Laser, Nonlinear Optics, and 4 moreHigh Frequency, X Rays, Doppler effect, and Gamma Ray
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The electron dynamics of laser wakefield acceleration (LWFA) is examined in the high-density regime using particle-in-cell simulations. These simulations model the electron source as a target of carbon nanotubes. Carbon nanotubes readily... more
The electron dynamics of laser wakefield acceleration (LWFA) is examined in the high-density regime using particle-in-cell simulations. These simulations model the electron source as a target of carbon nanotubes. Carbon nanotubes readily allow access to near-critical densities and may have other advantageous properties for potential medical applications of electron acceleration. In the near-critical density regime, electrons are accelerated by the ponderomotive force followed by the electron sheath formation, resulting in a flow of bulk electrons. This behavior represents a qualitatively distinct regime from that of low-density LWFA. A quantitative entropy index for differentiating these regimes is proposed. The dependence of accelerated electron energy on laser amplitude is also examined. For the majority of this study, the laser propagates along the axis of the target of carbon nanotubes in a 1D geometry. After the fundamental high-density physics is established, an alternative, 2...
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Nonlinear growth of the Parker instability (PI) and the Balbus…
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A new type of self-similar solution of ideal magnetohydrodynamics (MHD) in the nonlinear stage of the undular model (k parallel to B) of the magnetic buoyancy instability (the ballooning instability in fusion plasma physics or the Parker... more
A new type of self-similar solution of ideal magnetohydrodynamics (MHD) in the nonlinear stage of the undular model (k parallel to B) of the magnetic buoyancy instability (the ballooning instability in fusion plasma physics or the Parker instability in astrophysics) is found through MHD simulation and theory. The linear theory developed agrees well with the simulation in the early (linear) stage. The nonlinear stages of the instability in the simulation show the self-similar evolution. One of the solutions obtained from the nonlinear analysis has the characteristics of nonlinear instability in Lagrangian coordinates; the fluid velocity and the Alfven speed on each magnetic loop increase exponentially with time, because the loop is evacuated by the field-aligned motion of matter resulting from gravitational acceleration. In the later stage of the nonlinear evolution, the solution property changes from exponential to power-law time dependence. The latter corresponds to a force-free expansion solution. The later saturation of the velocity increment is also discussed.
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ABSTRACT
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ABSTRACT
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The effects of the beam-beam interaction on particle dynamics in a synchrotron collider are investigated. The main highlight of this work is the investigation of collective effects of the beam-beam interaction in a self-consistent... more
The effects of the beam-beam interaction on particle dynamics in a synchrotron collider are investigated. The main highlight of this work is the investigation of collective effects of the beam-beam interaction in a self-consistent approach that naturally incorporates the correct single particle dynamics. The most important target of this simulation is to understand and predict the long-time (108–109 rotations) behavior