| Paper | Title | Page |
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| TUPPH019 | Present Status of the Israeli FEL: Increasing FEL Power by Electron Beam Energy Boosting | 352 |
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| The status of R&D work aimed on increasing FEL power by boosting the electron beam energy after the radiation build-up is reported. A fine control of the electron beam energy during the radiation pulse is designed to compensate the small energy degradation during the pulse. Also, a controlled ramp (up or down) in the electron energy during the pulse will be applicable as well. Theoretical estimations of the output power in the presence of electron energy change during the pulse compared to the obtained experimental results are presented. 2 models, showing good agreement between them and with the existing data, are compared: low-gain analytical model based on the pendulum equation, and rigorous 3D FEL interaction model solved numerically. Another expected result of the design is to further extend the pulse duration with stable conditions and to obtain improved coherency. The electrical and mechanical lay-outs of the high-voltage boosting (leading to electron beam energy boosting) are also presented. | ||
| TUPPH018 | New Resonator for the Israeli FEL | 349 |
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| The Israeli FEL resonator was re-designed in order to reduce the overall round-trip losses and achieve control on the radiation output-coupling. In its new configuration, the resonator consists of overmoded corrugated rectangular waveguide and two radiation mode splitters, separating the high-energy e-beam from the laser radiation. The electron input splitter is based on Talbot effect in an overmoded rectangular waveguide. The radiation out-coupling is done in the output splitter. It is based on novel design and it combines Talbot effect between two parallel plates with free space propagation, and focusing by two curved cylindrical mirrors in a confocal imaging scheme. The waveguide and the splitters were tested experimentally, showing improved performance in comparison with the former resonator. The measured unloaded Q-factor of the new version is increased by a factor of ~ 3, attaining up to Q=30,000. Accordingly, the round-trip losses are ~15%. Rotating grids control the radiation out-coupling allowing wide variation for maximization of the radiation output power and extraction efficiency. The design layout and the testing results are presented. | ||
| THAAU05 | Space-Frequency Model of Ultra Wide-Band Interactions in Free-Electron Lasers | 513 |
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The principle of operation of intense radiation devices such as microwave tubes, free-electron lasers (FELs) and masers, is based on a distributed interaction between an electron beam and radiation. We developed a three-dimensional, space-frequency theory for the analysis and simulation of radiation excitation and propagation in electron devices and free-electron lasers operating in an ultra wide range of frequencies*. The total electromagnetic field is presented in the frequency domain as an expansion in terms of cavity eigen-modes. The mutual interaction between the electron beam and the field is fully described by coupled equations, expressing the evolution of mode amplitudes and electron beam dynamics. The approach is applied in a numerical particle code WB3D, simulating wide band interactions in free-electron lasers operating in the linear and non-linear regimes. The code is used to study the statistical and spectral characteristics of multimode radiation generation in a free-electron laser, operating in various operational parameters. The theory is demonstrated also in the case of "grazing", resulting in a wide-band interaction between the electron beam and the radiation.
* Y. Pinhasi, Yu. Lurie, A. Yahalom: Space-frequency model of ultra wide-band interactions in millimeter wave masers, Phys. Rev. E 71, (2005), 036503- 1-8 |
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