First Name: A.
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Last Name: Gover
Full Name: A. Gover
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8 papers
| title: | Virtual dielectric waveguide mode description of a high-gain free-electron laser. II. Modeling and numerical simulations |
| format: | journal article |
| year: | June 20, 2008 |
| 3 authors: | | | |
| abstract: | A high-gain free-electron laser is modeled using an expansion of the radiation field in terms of guided Laguerre-Gaussian modes of a virtual dielectric waveguide E. Hemsing, A. Gover, and J. Rosenzweig, preceding paper, Phys Rev. A 77, 063830 2008 . The radiation profile evolution, power gain, and detuning efficiency characteristics are investigated for seeding with fundamental Gaussian and higher-order Laguerre- Gaussian input modes on a Gaussian e-beam in the collective regime. The full wave evolution solution at different seed radiation injection conditions results in determination of the optimal waist size and waist position of the seed radiation beam for maximum power coupling efficiency. Results for guided mode evolution and power gain are shown to be consistent with simulations performed with the code GENESIS 1.3. The amplification and spontaneous generation of FEL radiation with orbital angular momentum is also considered. |
| keywords: | pbpl pra |
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| title: | Virtual dielectric waveguide mode description of a high-gain free-electron laser. I. Theory |
| format: | journal article |
| year: | June 20, 2008 |
| 3 authors: | | | |
| abstract: | A set of mode-coupled excitation equations for the slowly growing amplitudes of dielectric waveguide eigenmodes is derived as a description of the electromagnetic signal field of a high-gain free-electron laser FEL, including the effects of longitudinal space charge. This approach of describing the field basis set has notable advantages for FEL analysis in providing an efficient characterization of eigenmodes, and in allowing a clear connection to free-space propagation of the input seeding and output radiation. The formulation describes the entire evolution of the radiation wave through the linear gain regime, prior to the onset of saturation, with arbitrary initial conditions. By virtue of the flexibility in the expansion basis, this technique can be used to find the direct coupling and amplification of a particular mode. A simple transformation converts the derived coupled differential excitation equations into a set of coupled algebraic equations and yields a matrix determinant equation for the FEL eigenmodes. A quadratic index medium is used as a model dielectric waveguide to obtain an expression for the predicted spot size of the dominant system eigenmode, in the approximation that it is a single Gaussian mode. |
| keywords: | pbpl pra |
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| title: | Time and frequency domain analysis of superradiant coherent synchrotron radiation in a waveguide free-electron laser |
| format: | unknown |
| year: | 1994 |
| 6 authors: | | | | | | |
| abstract: | The coherent synchrotron radiation process in a waveguide is theoretically investigated. A single, short bunch propagating through a wiggler is considered. In a waveguide, two very distinct regimes are possible. At grazing, where the beam velocity matches the wave group velocity, the bunch emits a single, ultrashort chirped pulse whose duration is determined by the interaction bandwidth and the waveguide dispersion. Away from grazing, where slippage dominates, two distinct pulses are radiated at the Doppler upshifted and downshifted frequencies. Both the time and frequency domain expressions for the radiation characteristics are derived. (13 References). |
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| title: | Three dimensional simulation of high harmonic transverse optical klystron |
| format: | conference procceeding |
| conference: | 9th International Free Electron Laser Conference |
| year: | 1988 |
| 4 authors: | | | | |
| abstract: | We present the results of a three dimensional simulation code, which calculates the parameters of coherent super-radiant harmonic frequency emission by electrons which are being bunched by an external laser beam while propagating in a planar undulator. This code was written in order to simulate the TOK experiment, which is presently underway at BNL. Instead of a full numerical simulation of Maxwell's equations and the electron force equations, a semi-analytical approach is adopted. Electron trajectories are computed analytically, and the radiation fields are expanded in terms of free space eigenmodes. Phase space and energy profiles of the electron beam are incorporated by a variable space sampling according to a given distribution function, rather than via Monte Carlo simulation. Computation time of about 0.1 s/electron was achieved with the present version of the code on the IBM 3090. We present the expected radiometric parameters as a function of the electron beam parameters (emittance and energy spread), and the modulating laser beam parameters (Rayleigh length, waist position and power). Statistical averaging is carried out by weighted averaging of the initial electron moments and energy phase space distribution. This approach results in the best prediction of the expected experimental measurement of the optical parameters which can be achieved with a finite number of sampling electrons (much smaller than in the experiment), without introducing artificial noise as in the Monte Carlo approach. |
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| title: | Helical Electron-Beam Microbunching by Harmonic Coupling in a Helical Undulator |
| format: | journal article |
| year: | April 29, 2009 |
| 7 authors: | | | | | | | |
| abstract: | Microbunching of a relativistic electron beam into a helix is examined analytically and in simulation. Helical microbunching is shown to occur naturally when an e beam interacts resonantly at the harmonics of the combined field of a helical magnetic undulator and an axisymmetric input laser beam. This type of interaction is proposed as a method to generate a strongly prebunched e beam for coherent emission of light with orbital angular momentum at virtually any wavelength. The results from the linear microbunching theory show excellent agreement with three-dimensional numerical simulations. |
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| title: | Helical Electron-Beam Microbunching by Harmonic Coupling in a Helical Undulator |
| format: | journal article |
| year: | 2009 |
| 7 authors: | | | | | | | |
| abstract: | Microbunching of a relativistic electron beam into a helix is examined analytically and in simulation. Helical microbunching is shown to occur naturally when an e beam interacts resonantly at the harmonics of the combined field of a helical magnetic undulator and an axisymmetric input laser beam. This type of interaction is proposed as a method to generate a strongly prebunched e beam for coherent emission of light with orbital angular momentum at virtually any wavelength. The results from the linear microbunching theory show excellent agreement with three-dimensional numerical simulations. |
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| title: | Virtual dielectric waveguide mode description of a high-gain free-electron laser. |
| format: | journal article |
| year: | 2008 |
| 3 authors: | | | |
| abstract: | A high-gain free-electron laser is modeled using an expansion of the radiation field in terms of guided Laguerre-Gaussian modes of a virtual dielectric waveguide E. Hemsing, A. Gover, and J. Rosenzweig, preceding paper, Phys Rev. A 77, 063830 2008 . The radiation profile evolution, power gain, and detuning efficiency characteristics are investigated for seeding with fundamental Gaussian and higher-order Laguerre-Gaussian input modes on a Gaussian e-beam in the collective regime. The full wave evolution solution at different seed radiation injection conditions results in determination of the optimal waist size and waist position of the seed radiation beam for maximum power coupling efficiency. Results for guided mode evolution and power gain are shown to be consistent with simulations performed with the code GENESIS 1.3. The amplification and spontaneous generation of FEL radiation with orbital angular momentum is also considered. |
| keywords: | |
| Download | View | Details | edit | delete | |
| title: | Virtual dielectric waveguide mode description of a high-gain free-electron laser. I. Theory |
| format: | journal article |
| year: | 2008 |
| 3 authors: | | | |
| abstract: | A set of mode-coupled excitation equations for the slowly growing amplitudes of dielectric waveguide eigenmodes is derived as a description of the electromagnetic signal field of a highgain free-electron laser FEL , including the effects of longitudinal space charge. This approach of describing the field basis set has notable advantages for FEL analysis in providing an efficient characterization of eigenmodes, and in allowing a clear connection to free-space propagation of the input seeding and output radiation. The formulation describes the entire evolution of the radiation wave through the linear gain regime, prior to the onset of saturation, with arbitrary initial conditions. By virtue of the flexibility in the expansion basis, this technique can be used to find the direct coupling and amplification of a particular mode. A simple transformation converts the derived coupled differential excitation equations into a set of coupled algebraic equations and yields a matrix determinant equation for the FEL eigenmodes. A quadratic index medium is used as a model dielectric waveguide to obtain an expression for the predicted spot size of the dominant system eigenmode, in the approximation that it is a single Gaussian mode. |
| keywords: | |
| Download | View | Details | edit | delete | |