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Tapering effects of a Plasma Density in Laser Wakefield
Hyyong Suk,Hae June Lee 한국물리학회 2004 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.44 No.52
In laser wakeeld acceleration, controlling the accelerated beam quality is an important issue. Generally, high energy beams produced by laser wakeeld acceleration are known to have a fairly low emittance, but the energy spread is rather large. Hence, it would be very good if the beam energy spread could be controlled somehow. In this paper, such a method to control the beam quality is presented, i.e., the downward density tapering method is introduced. In addition, a method to increase the beam energy is introduced. In this method, the density tapering is upward so that the accelerated beam is kept within the acceleration phase of the wakeeld. Therefore, signicantly higher energies can be achieved. Results are presented.
Laser-Produced Plasma Diffusion across a Transverse Magnetic Field
Devki Gupta,Hyyong Suk 한국물리학회 2005 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.47 No.6
A one-dimensional numerical result for laser-produced plasma diffusion across a transverse uniform magnetic field is presented. The laser with a Gaussian distribution of intensity perpendicular to the direction of propagation creates a plasma, which is allowed to expand across a transverse magnetic field. As the laser beam propagates, the density of electrons decreases on the axis, and a plasma channel evolves. The spatial and the temporal behaviors of the plasma parameters, like the electron density and the velocity, with the radial distance from the channel axis in the presence of a magnetic field are reported. The results, experimental and simulated, are compared and are found to be in reasonable agreement.
Design of a Dielectric Laser Accelerator with the On-chip Pulse-front-tilt Method
Yu Hyungyu,Suk Hyyong 한국물리학회 2022 새물리 Vol.72 No.8
In this research, a photonic crystal for dielectric laser accelerator has been designed and analyzed by conducting finite-domain-time-differential (FDTD) simulations. The photonic crystal of dielectric materials, such as Si or SiO2, can confine electric field components of a laser pulse in space when it is designed as a cavity structure. The longitudinal electric field components can serve as a driving force for electrons. A maximum acceleration gradient is expected when the electron and acceleration field phases are matched. The phase matching can be achieved by tilting the front of the input laser pulse. In this study, a combined structure of a micro-scale prism and periodic cavities was considered to tilt the pulse front. The calculation of the acceleration field by FDTD simulations can give an energy gain of the incident electrons in dielectric laser acceleration (DLA).
Formation of relativistic electron mirrors in laser-plasma
Victor V. Kulagin,Hyyong Suk 한국물리학회 2004 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.44 No.52
The generation of relativistic electron mirrors (bunches with extremely short lengths) in laserplasma interactions is considered. It is shown that such a mirror can be generated by using an ultra-intense nonadiabatic laser pulse (pulse with a sharp rising edge) incident normally upon a thin plasma layer. Due to the relativistic contraction, the resulting length of the electron mirror can be considerably smaller than the initial thickness of the plasma layer. The lifetime of the relativistic mirror depends on the dimensionless amplitude and shape of the laser pulse, the initial density of electrons, and the thickness of the plasma layer. As a result, relativistic electron mirrors can survive during the rst several half-periods of an external electromagnetic eld, which can correspond to time intervals of hundreds of femtoseconds in the laboratory frame.
Stability of Relativistic Solitons in Three Species Plasma
Jincheol B. Kim,Hae June Lee,Hyyong Suk,In Soo Ko 한국물리학회 2004 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.44 No.52
An extended 1D kinetic model of relativistic solitons in three-species plasmas is suggested, and the stability condition of the solitons is derived. The range of parameters for stable solitons are specied in the frequency-temperature plane. The regions for solitons in electron-positron-ion plasmas and negative ion plasmas are calculated and specied. With the insertion of another species of charged particles into the plasmas, relativistic solitons appear stable over a wider range of frequencies and temperatures. In electron-positron-ion plasmas, the regions are expanded toward higher values in the frequency-temperature plane. In negative ion plasmas, the regions are broadened only at higher temperatures, which results from the heavy mass of the negative ions. The stability conditions are aected by both the mixing ratio m and the net charge of the third species.
Simulations of the Raman Backward Amplifier Using the Parallelized Averaged-Particle-In-Cell Model
Min Sub Hur,Ilmoon Hwang,Hyyong Suk 한국물리학회 2005 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.47 No.4
A new version of the averaged particle-in-cell (aPIC) code has been developed to simulate the Raman backscatter (RBS) and the Raman backward laser amplification in plasmas. We observe in the aPIC simulations that the RBS coupling is weakened by the electron trapping, that is generated by wave-breaking. As a result, the amplification level is significantly reduced. In this paper, a physical interpretation of the trapping-induced RBS weakening is presented. In the numerical point of view, the new aPIC, which is a completely parallelized code, shows a parallelization efficiency that is notably improved from that of the semi-parallelized old aPIC.