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H Mehdian - One of the best experts on this subject based on the ideXlab platform.
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investigation of the Electron Trajectories and gain regimes of the whistler pumped free Electron laser
Physics of Plasmas, 2013Co-Authors: F Jafarinia, S Jafari, H MehdianAbstract:A free-Electron laser (FEL) scheme, which employs the whistler wave as a slow electromagnetic wave wiggler, was studied theoretically. Subjected to the transverse fields of whistler wave wiggler, the beam Electrons are the source of the energy needed to produce electromagnetic radiation. The strength and the period of the wiggler field depend on the parameters of the magnetoplasma medium. This configuration has a higher tunability by controlling the plasma density, on top of the γ-tunability of the conventional FELs. The theory of linear gain and Electron Trajectories was presented and four groups (I, II, III, and IV) of Electron orbits were found in the presence of an axial guide magnetic field. Using perturbation analysis, it is found that these groups of orbits were stable except small regions of group I and IV orbits. The function Φ which determines the rate of change of axial velocity with beam energy was also derived. In the case in which Φ<0 represents a negative-mass regime in which the axial velo...
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steady state Electron Trajectories and growth rate in electromagnetically pumped free Electron laser with specific nonuniform magnetic field
Physics of Plasmas, 2008Co-Authors: H Mehdian, S Jafari, A HasanbeigiAbstract:A theory of the dispersion relation for electromagnetically pumped free-Electron laser in the presence of a special tapered axial guide magnetic field is presented. An analysis of the steady-state Electron Trajectories is obtained by solving the equations of motion. Next an eleventh-degree polynomial equation for electromagnetic and space-charge wave is derived. Numerical solution of the polynomial equation of the dispersion relation yield the complex wave number as a function of the frequency of the waves. These results are used to illustrate the dependence of growth rate curves on the axial guide field frequency. It is found that the tapered guide field shifts Electron Trajectories and enhances the growth rate in the comparison of employing uniform axial magnetic field, without needing a strong guide magnetic field.
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chaotic Electron Trajectories in a planar wiggler free Electron laser
Acta Physica Polonica A, 2006Co-Authors: A Soleyman, H MehdianAbstract:The motion of an Electron in a planar wiggler with an axial guide field is found to be nonintegrable. When taking into account the effects of self-fields of the beam, it is confirmed that the motion of an Electron in a planar wiggler with a guide field may be chaotic. There is evidence of chaos from numerical calculations of nonzero Lyapunov exponents using different approaches of Benettin’s method which are described and compared. Very accurate Poincare maps are also performed.
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Electron Trajectories in a free Electron laser with helical wiggler ion channel guiding and parallel reversed axial magnetic field
Journal of Plasma Physics, 2004Co-Authors: Mahdi Esmaeilzadeh, H Mehdian, Joseph E WillettAbstract:An analysis of Electron Trajectories in a helical magnetic wiggler with a uniform ion channel and a uniform axial magnetic field is presented. The axial field is considered in both the conventional and reversed directions. Equations for the transverse coordinates and velocities of a single relativistic Electron in the combined ion electrostatic field and helical and axial magnetic fields are derived. A sixth-degree polynomial equation for the Electron velocity and an equation for the function Φ (which determines the rate of change if axial velocity with energy) are derived. Results of some numerical calculations are presented to illustrate the effects of the electrostatic field and the axial magnetic field in each of the two configurations.
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Electron Trajectories in a free Electron laser with planar wiggler and ion channel guiding
Physics of Plasmas, 2001Co-Authors: H Mehdian, Mehdi Esmelzadeh, Joseph E WillettAbstract:An analysis of quasi-steady-state Electron Trajectories in a planar wiggler with an ion channel and an axial magnetic field is presented. A tenth-degree polynomial equation for the average axial Electron velocity and an equation for the function Φ, which determines the rate of change of axial velocity with energy, are derived. Numerical calculations are made to illustrate the effects of the two Electron-beam guiding devices on the Trajectories when applied separately and simultaneously. Some interesting effects of their simultaneous application include the existence of three groups of orbits, two singularities of the function Φ, and two negative mass regimes.
S Jafari - One of the best experts on this subject based on the ideXlab platform.
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Electron Trajectories and growth rates of the plasma wave pumped free Electron laser
Plasma Physics and Controlled Fusion, 2014Co-Authors: S Jafari, F Jafarinia, M Nilkar, M AmiriAbstract:A theory for a plasma wave wiggler has been described which employs the plasma whistler wave for producing laser radiation in a free-Electron laser (FEL). While electromagnetically pumped FELs have been proven to be an effective means generating short wavelengths, practical difficulties occur in the design of these wigglers. For this reason, it is found that a plasma wave wiggler can be employed in concept with an electromagnetic wave wiggler due to both higher tunability and holding the focus of pump wave and e-beam over a significant distance to achieve a suitable amplification. Plasma in the presence of static magnetic field supports a plasma whistler wave. The plasma wiggler period can be tuned by varying the plasma density and/or ambient magnetic field. Electron Trajectories have been analyzed using single particle dynamics and regimes of orbital stability have been demonstrated. A polynomial dispersion relation for electromagnetic and space-charge waves has then been derived, analytically. Numerical studies of the dispersion relation reveal that the growth rates are sensitive functions of the cyclotron frequency. It has been shown that by increasing the axial magnetic field strength (or cyclotron frequency), the growth rate for groups I and III orbits increases, while a growth decrement has been obtained for groups II and IV orbits.
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Investigation of the Electron Trajectories and gain regimes of the whistler pumped free-Electron laser
Physics of Plasmas, 2013Co-Authors: F Jafarinia, S Jafari, Hassan MehdianAbstract:A free-Electron laser (FEL) scheme, which employs the whistler wave as a slow electromagnetic wave wiggler, was studied theoretically. Subjected to the transverse fields of whistler wave wiggler, the beam Electrons are the source of the energy needed to produce electromagnetic radiation. The strength and the period of the wiggler field depend on the parameters of the magnetoplasma medium. This configuration has a higher tunability by controlling the plasma density, on top of the γ-tunability of the conventional FELs. The theory of linear gain and Electron Trajectories was presented and four groups (I, II, III, and IV) of Electron orbits were found in the presence of an axial guide magnetic field. Using perturbation analysis, it is found that these groups of orbits were stable except small regions of group I and IV orbits. The function Φ which determines the rate of change of axial velocity with beam energy was also derived. In the case in which Φ
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investigation of the Electron Trajectories and gain regimes of the whistler pumped free Electron laser
Physics of Plasmas, 2013Co-Authors: F Jafarinia, S Jafari, H MehdianAbstract:A free-Electron laser (FEL) scheme, which employs the whistler wave as a slow electromagnetic wave wiggler, was studied theoretically. Subjected to the transverse fields of whistler wave wiggler, the beam Electrons are the source of the energy needed to produce electromagnetic radiation. The strength and the period of the wiggler field depend on the parameters of the magnetoplasma medium. This configuration has a higher tunability by controlling the plasma density, on top of the γ-tunability of the conventional FELs. The theory of linear gain and Electron Trajectories was presented and four groups (I, II, III, and IV) of Electron orbits were found in the presence of an axial guide magnetic field. Using perturbation analysis, it is found that these groups of orbits were stable except small regions of group I and IV orbits. The function Φ which determines the rate of change of axial velocity with beam energy was also derived. In the case in which Φ<0 represents a negative-mass regime in which the axial velo...
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steady state Electron Trajectories and growth rate in electromagnetically pumped free Electron laser with specific nonuniform magnetic field
Physics of Plasmas, 2008Co-Authors: H Mehdian, S Jafari, A HasanbeigiAbstract:A theory of the dispersion relation for electromagnetically pumped free-Electron laser in the presence of a special tapered axial guide magnetic field is presented. An analysis of the steady-state Electron Trajectories is obtained by solving the equations of motion. Next an eleventh-degree polynomial equation for electromagnetic and space-charge wave is derived. Numerical solution of the polynomial equation of the dispersion relation yield the complex wave number as a function of the frequency of the waves. These results are used to illustrate the dependence of growth rate curves on the axial guide field frequency. It is found that the tapered guide field shifts Electron Trajectories and enhances the growth rate in the comparison of employing uniform axial magnetic field, without needing a strong guide magnetic field.
J M Buzzi - One of the best experts on this subject based on the ideXlab platform.
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Electron Trajectories in a free Electron laser with a reversed axial guide field
Physical Review E, 1993Co-Authors: V A Bazylev, A Bourdier, P Gouard, J M BuzziAbstract:In order to interpret an experiment of Conde and Bekefi [Phys. Rev. Lett. 67, 3082 (1991); 68, 418 (E) (1992)], Electron Trajectories are studied for a configuration with a reversed axial guide field. First, ignoring the radial dependence of the wiggler, an analytic model is constructed. The results are discussed and compared with those of numerical simulations. Close to ``antiresonance,'' two types of Electron Trajectories are considered and discussed. One type corresponds to a linearly polarized motion and leads to a moderate coupling with the radiation field. This first part shows how Electrons, which remain close to the axis of the beam, can contribute to the observed dip in the power output. Then the radial dependence of the wiggler is considered. In the vicinity of ``antiresonance,'' Electrons are shown to have ``chaotic'' Trajectories when emitted far enough from the axis. As a consequence, the interaction efficiency is degraded for most particles. This explains the large dip in radiative power observed and predicted by our simulation computer code. The radial dependence also gives a possible explanation for the very good efficiency observed in the experiment.
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Electron Trajectories in a free Electron laser with a reversed axial guide field
Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment, 1993Co-Authors: V A Bazylev, A Bourdier, J M Buzzi, P GouardAbstract:Abstract In order to interpret the experiment of Conde and Bekefi, Electron Trajectories are studied for a configuration with a reversed axial guide field. First, ignoring the radial dependence of the wiggler, an analytic model is constructed. The results are discussed and compared with those of numerical simulations. This first part shows how Electrons, which remain close to the axis of the beam, can contribute to the dip in the power output observed. Then, the radial dependence of the wiggler is considered. In the vicinity of “anti-resonance”, Electrons are shown to have “chaotic” Trajectories when emitted far enough from the axis. Thus, the interaction efficiency is degraded for most particles. This explains the large dip in radiative power observed and predicted by our simulation code. The radial dependence also gives a possible explanation for the very good efficiency observed in the experiment.
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Electron Trajectories in a free Electron laser with a reversed axial guide field
Physical Review A, 1993Co-Authors: V A Bazylev, A Bourdier, P Gouard, J M BuzziAbstract:In order to interpret an experiment of Conde and Bekefi [Phys. Rev. Lett. 67, 3082 (1991); 68, 418 (E) (1992)], Electron Trajectories are studied for a configuration with a reversed axial guide field. First, ignoring the radial dependence of the wiggler, an analytic model is constructed. The results are discussed and compared with those of numerical simulations. Close to «antiresonance,» two types of Electron Trajectories are considered and discussed. One type corresponds to a linearly polarized motion and leads to a moderate coupling with the radiation field. This first part shows how Electrons, which remain close to the axis of the beam, can contribute to the observed dip in the power output. Then the radial dependence of the wiggler is considered
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chaotic Electron Trajectories in a free Electron laser
Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment, 1991Co-Authors: L Michel, A Bourdier, J M BuzziAbstract:Abstract It is confirmed that, when the equilibrium self-fields are taken into account, the motion of an Electron in a helical wiggler with guide field may be chaotic. Only two independent constants of motion in involution were found. Also, there is evidence of chaos from numerical calculations of Poincare maps and nonzero Liapunov exponents. The trajectory of an Electron in a linearly polarized wiggler with guide field is, however, found to be nonintegrable. Resonances can be predicted from a one-dimensional Hamiltonian perturbed by a small “time” dependent quantity.
F Jafarinia - One of the best experts on this subject based on the ideXlab platform.
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Electron Trajectories and growth rates of the plasma wave pumped free Electron laser
Plasma Physics and Controlled Fusion, 2014Co-Authors: S Jafari, F Jafarinia, M Nilkar, M AmiriAbstract:A theory for a plasma wave wiggler has been described which employs the plasma whistler wave for producing laser radiation in a free-Electron laser (FEL). While electromagnetically pumped FELs have been proven to be an effective means generating short wavelengths, practical difficulties occur in the design of these wigglers. For this reason, it is found that a plasma wave wiggler can be employed in concept with an electromagnetic wave wiggler due to both higher tunability and holding the focus of pump wave and e-beam over a significant distance to achieve a suitable amplification. Plasma in the presence of static magnetic field supports a plasma whistler wave. The plasma wiggler period can be tuned by varying the plasma density and/or ambient magnetic field. Electron Trajectories have been analyzed using single particle dynamics and regimes of orbital stability have been demonstrated. A polynomial dispersion relation for electromagnetic and space-charge waves has then been derived, analytically. Numerical studies of the dispersion relation reveal that the growth rates are sensitive functions of the cyclotron frequency. It has been shown that by increasing the axial magnetic field strength (or cyclotron frequency), the growth rate for groups I and III orbits increases, while a growth decrement has been obtained for groups II and IV orbits.
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Investigation of the Electron Trajectories and gain regimes of the whistler pumped free-Electron laser
Physics of Plasmas, 2013Co-Authors: F Jafarinia, S Jafari, Hassan MehdianAbstract:A free-Electron laser (FEL) scheme, which employs the whistler wave as a slow electromagnetic wave wiggler, was studied theoretically. Subjected to the transverse fields of whistler wave wiggler, the beam Electrons are the source of the energy needed to produce electromagnetic radiation. The strength and the period of the wiggler field depend on the parameters of the magnetoplasma medium. This configuration has a higher tunability by controlling the plasma density, on top of the γ-tunability of the conventional FELs. The theory of linear gain and Electron Trajectories was presented and four groups (I, II, III, and IV) of Electron orbits were found in the presence of an axial guide magnetic field. Using perturbation analysis, it is found that these groups of orbits were stable except small regions of group I and IV orbits. The function Φ which determines the rate of change of axial velocity with beam energy was also derived. In the case in which Φ
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investigation of the Electron Trajectories and gain regimes of the whistler pumped free Electron laser
Physics of Plasmas, 2013Co-Authors: F Jafarinia, S Jafari, H MehdianAbstract:A free-Electron laser (FEL) scheme, which employs the whistler wave as a slow electromagnetic wave wiggler, was studied theoretically. Subjected to the transverse fields of whistler wave wiggler, the beam Electrons are the source of the energy needed to produce electromagnetic radiation. The strength and the period of the wiggler field depend on the parameters of the magnetoplasma medium. This configuration has a higher tunability by controlling the plasma density, on top of the γ-tunability of the conventional FELs. The theory of linear gain and Electron Trajectories was presented and four groups (I, II, III, and IV) of Electron orbits were found in the presence of an axial guide magnetic field. Using perturbation analysis, it is found that these groups of orbits were stable except small regions of group I and IV orbits. The function Φ which determines the rate of change of axial velocity with beam energy was also derived. In the case in which Φ<0 represents a negative-mass regime in which the axial velo...
Mahdi Esmaeilzadeh - One of the best experts on this subject based on the ideXlab platform.
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chaotic Electron Trajectories in an electromagnetic wiggler free Electron laser with ion channel guiding
Physics of Plasmas, 2010Co-Authors: Amin Taghavi, Mahdi Esmaeilzadeh, Mohammad S FallahAbstract:Chaotic behavior of an Electron motion in combined backward propagating electromagnetic wiggler and ion-channel electrostatic fields is studied. The Poincare surface-of-sections are employed to investigate chaotic behavior of Electron motion. It is shown that the Electron motion can exhibit chaotic behavior when the ion-channel density is low or medium, while for sufficiently high ion-channel density, the Electron motion becomes regular (nonchaotic). Also, the chaotic Trajectories decrease when the effects of self-fields of Electron beam are taken into account and under Budker condition all Trajectories become regular. The above result is in contrast with magnetostatic helical wiggler with axial magnetic field in which chaotic motion is produced by self-fields of Electron beam. The chaotic and nonchaotic Electron Trajectories are confirmed by calculating Liapunov exponents.
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chaotic Electron Trajectories in a free Electron laser with helical wiggler and ion channel guiding
Journal of Plasma Physics, 2006Co-Authors: Mohammad S Fallah, Mahdi Esmaeilzadeh, Joseph E Willett, Lori Jo WillettAbstract:An analysis of relativistic Electron Trajectories in a free-Electron laser with a helical magnetic wiggler and an ion channel is presented. The wiggler field amplitude and the ion number density are taken to be uniform. Also included are the self-electric and self-magnetic fields of the Electron beam, which is assumed to be of constant velocity and Electron number density. The Hamiltonian, which is a constant of the motion, is first expressed in cartesian coordinates and momenta. A second constant of the motion is obtained by canonical transformation. The steadystate orbits, Poincare maps, and Liapunov exponents are employed to investigate the chaotic motion in the presence of the ion channel. Numerical calculations reveal conditions under which chaotic and non-chaotic orbits exist.
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Electron Trajectories and gain for an electromagnetic wiggler with ion channel guiding
Physics of Plasmas, 2006Co-Authors: Mahdi Esmaeilzadeh, Vahid Ghafouri, Amin Taghavi, Esmaeil NamvarAbstract:A theory is developed for a free-Electron laser with electromagnetic wiggler and ion-channel guiding. The Electron Trajectories due to a large amplitude backward propagating electromagnetic wiggler and an ion-channel electrostatic field are obtained and the stability of orbits is discussed. Then the gain equation describing the interaction between an Electron and the radiation field is derived in the low-gain-per-pass limit. The results of a numerical study of Electron orbits and gain are presented and discussed. It is shown that the maximum gain obtained in an electromagnetic wiggler is about twice the maximum gain obtained in a magnetostatic wiggler.
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Electron Trajectories in a free Electron laser with helical wiggler ion channel guiding and parallel reversed axial magnetic field
Journal of Plasma Physics, 2004Co-Authors: Mahdi Esmaeilzadeh, H Mehdian, Joseph E WillettAbstract:An analysis of Electron Trajectories in a helical magnetic wiggler with a uniform ion channel and a uniform axial magnetic field is presented. The axial field is considered in both the conventional and reversed directions. Equations for the transverse coordinates and velocities of a single relativistic Electron in the combined ion electrostatic field and helical and axial magnetic fields are derived. A sixth-degree polynomial equation for the Electron velocity and an equation for the function Φ (which determines the rate of change if axial velocity with energy) are derived. Results of some numerical calculations are presented to illustrate the effects of the electrostatic field and the axial magnetic field in each of the two configurations.