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| MOPPH011 | Comparison Between Kinetic and Fluid Description of Plasma-Loladed Free-Electron Laser | radiation, electron, wiggler, space-charge | 42 | |||||
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In the kinetic treatment of the plasma-loaded FEL in Ref.* single particle equation of motion, for both beam and plasma electrons in the radiation fields, are used. Therefore, interaction terms between the wiggler and the space-charge wave, in the transverse velocity of electrons, which are important elements in the fluid model, are neglected. A dispersion relation of a plasma-loaded FEL with kinetic theory is found in Ref.* that takes into account the velocity spread of both beam and plasma electrons. In the present analysis, a dispersion relation is obtained, by the fluid theory, with the interaction terms between the wiggler and the space-charge wave in the transverse velocity of electrons taken into account. Since these interaction terms are inherently missing in the kinetic theory the two dispersion relation are compared to find out about the importance of these terms. It was found that although the absence of these terms has considerable effects on the growth rate, the general kinetic dispersion relation may be used to study the temperature effects of a warm beam/plasma on the instability of a free-electron laser with a plasma background.
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* S. Babaei and B. Maraghechi, "Kinetic description of plasma-loaded free-electron laser", Phys. Plasmas, to be published. |
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| MOPPH012 | Conservation Laws in Quasilinear Theory of Raman Free-Electron Laser | electron, space-charge, free-electron-laser, laser | 46 | |||||
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A quasilinear theory of the free-electron laser, in Raman regime, is presented to establish that conservation laws on number, energy, and momentum are upheld. A high density electron beam is assumed so that the space-charge potential is no longer negligible. A sufficiently broad band spectrum of waves is assumed so that saturation will be due to the quasilinear spread of the beam electrons. Otherwise, for the single mode excitation, saturation will be due to the electron trapping in the space-charge potential. It is shown that the quasilinear slow variation of the background distribution function is in the form of the diffusion equation in momentum space. An expression for the time evolution of the spectral energy density is derived. Conservation laws to the quasilinear order (second order) are derived and are proved to be satisfied. Results of the present investigation may be used to study the quasilinear saturation of free-electron laser in the presence of the space-charge wave.
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| TUCAU01 | FELs and High-energy Electron Cooling | electron, hadron, collider, proton | 268 | |||||
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Electron cooling is extremely successful in cooling low and medium energy ions, including protons. ERLs are promising to extend the reach of traditional electron cooling to about 100 GeV/nucleon for heavy ions. Nevertheless, cooling of protons with energies from about 100 GeV (RHIC) to few TeV (LHC) becoming very complicated or even possible. Optical stochastic cooling [1] has potential to be an instrument of choice, but it has two main shortcomings: a) it requires significant modifications of the lattices of hadron machine and b) in the case of the protons it suffers from very inefficient interaction (radiation) of protons with TEM wave. It was suggested [2] to combine advantages of electrostatic interaction with broad-band FEL-amplifier in what is now called stochastic electron cooling. Such system will naturally fit into a straight section of modern high energy hadron colliders. In this paper we present description of the cooling process and give examples of FEL-based electron cooler for protons in RHIC and LHC. [1] A. Mikhalichenko and M. Zolotorev, Phys. Rev. Lett., 71, p.4146 (1993). [2] Ya. S. Derbenev, NIM A441 (2000) 223
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| WEAAU05 | A Compact Electron Spectrometer for an LWFA | electron, laser, radiation, undulator | 294 | |||||
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The use of a laser wakefield accelerator (LWFA) beam as a driver for a compact Free-Electron Laser (FEL) has been proposed recently. A project is underway at Argonnne National Laboratory (ANL) to operate an LWFA in the bubble regime and to use the quasi-monoenergetic electron beam as a driver for a 3-m long undulator for generation of sub-ps UV radiation. The Terawatt Ultrafast High Field Facility (TUHFF) in the Chemistry division provides the 20 TW peak power laser. Towards this goal, a compact electron spectrometer whose initial fields of 0.45 T provide energy coverage of 30-200 MeV has been selected to characterize the electron beams. The system is based on the Ecole Polytechnique design* used for their LWFA and incorporates the 5-cm long permanent magnet dipole, the LANEX scintillator screen located at the dispersive plane, a Roper Scientific 16-bit MCP-intensified CCD camera, and a Bergoz ICT for complementary charge measurements. Test results on the magnets, the 16-bit camera, and the ICT will be described, and initial electron beam data will be presented as available.
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*Y. Glinnec et al., "Broadrange Single Shot Electron Spectrometer", Report dated July 6, 2006, Ecole Polytechnique. |
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