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A Numerical Study of the Integral Equations for the Laser Fields in Free-electron Lasers
Jaegwon Yoo,이병철,박성희,조성오,Y. J. Rhee,정영욱 한국물리학회 2004 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.44 No.6
The dynamics of the radiation elds in free-electron lasers is investigated on the basis of the integro-differential equations in the one-dimensional formulation. For simple cases we solved the integro-differential equations analytically and numerically to test our numerical procedures developed on the basis of the Filon method. The numerical results showed good agreement with the analytical solutions. To confirm the legitimacy of the numerical package, we carried out numerical studies on the inhomogeneous broadening effects, where no analytic solutions are available, due to the energy spread and the emittance of the electron beam.
Numerical Study of Thermal Wave Propagation in a Disc Slab Irradiated by Ultrashort Laser Pulses
Jaegwon Yoo,C. H. Lim,Cheoljung Kim 한국물리학회 2005 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.47 No.1
To study the physical processes in ultrashort laser irradiation of a material, we developed a thermal wave solution of the hyperbolic heat conduction equation in a ¯nite medium on the basis of the Green's function formalism. With the 3-dimensional Green's function, numerical computations were carried out to investigate the temperature response and the propagation of the thermal wave due to the heat pulse generated by a laser pulse with various laser pulse durations. We present numerical results of the thermal wave propagation on the surface of and inside a ¯nite slab. We discuss the role of the thermal relaxation time in ultrashort laser-based material processing and the optimal pulse duration to minimize thermal in°uences.
Numerical Simulation of Laser Resonators
Jaegwon Yoo,이병철,조성오,Y Rhee,정영욱 한국물리학회 2004 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.44 No.2
We developed numerical simulation packages for laser resonators on the bases of a pair of integral equations. Two numerical schemes, a matrix formalism and an iterative method, were programmed for nding numeric solutions to the pair of integral equations. The iterative method was tried by Fox and Li, but it was not applicable for high Fresnel numbers since the numerical errors involved propagate and accumulate uncontrollably. In this paper, we implement the matrix method to extend the computational limit further. A great number of case studies are carried out with various congurations of stable and unstable resonators to compute diractional losses, phase shifts, intensity distributions and phases of the radiation elds on mirrors. Our results presented in this paper show not only a good agreement with the results previously obtained by Fox and Li, but also the legitimacy of our numerical procedures for high Fresnel numbers.
Numerical Simulations of the Electron Dynamics in Free-electron Lasers
Jaegwon Yoo,B. C. Lee,S. H. Park,Y. U. Jeong 한국물리학회 2004 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.45 No.2
The dynamics of the electrons in free-electron lasers (FELs) is investigated on the basis of the pendulum equation to study the satuared state of a high-gain FEL. The phase-space evolution and the bunching coecients of the electrons, which enable one to obtain the evolution of the radiation eld, are brie y reviewed. Describing the computational procedures for solving the FEL pendulum equation numerically, we discuss the electron dynamics and the evolutions of the radiation eld in various gain regions and saturation regions.
Thermoelastic Surface Waves Generated by Irradiation with a Line-Focused Laser Pulse
Jaegwon Yoo,C. H. Lim,S. H. Baik 한국물리학회 2006 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.48 No.I
A numerical analysis formulation has been developed to simulate the generation of thermoelastic surface waves in a homogeneous isotropic elastic half-space under a line-focused laser irradiation. Analytic solutions for surface displacements are obtained by applying integral transform methods to the transient elastodynamic equations. The inverse Fourier transform is numerically evaluated by making use of Filon's method, and a numerical inversion of the Laplace transform is performed on the basis of the Crump-Durbin technique. We present the numerical results for the displacements and the tractions generated by a line-focused laser pulse irradiating the surface of an aluminium block.
조성오,ByungCheolLee,YoungUkJeong,JaegwonYoo,SeongHeePark 한국물리학회 2002 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.41 No.5
An energy-recovering superconducting linear accelerator is being developed for a high-power infrared free-electron laser (FEL). The design value of the maximum beam current circulating in the superconducting cavities is 50 mA. In such a high-current accelerator, the wakefield excited by the bunches passing through the cavities can induce unstable operation of the accelerator. The effects of the wakefield on the accelerator operation are analyzed for successful lasing of the FEL. The beam quality degradation, the starting current of the beam breakup, and the power loss to the higher-order mode coupler are calculated analytically and numerically. It is found that the accelerator can be operated at the maximum current without having a severe problem caused by the wakefield.