Improvement of nonlinear harmonics in free electron laser with planar wiggler

Journal of Applied Physics

Maraghechi

2013

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The effect of axial energy spread on the radiation of third harmonic is studied in the free electron laser with planar wiggler and ion-channel guiding. Spread in the longitudinal momentum and so in the initial energy of electron beam, without any spread in the transverse velocity, is assumed in the form of Gaussian distribution function. The technique that is employed is a one-dimensional and steady-state simulation. A set of self consistent nonlinear differential equations that describes the system is solved numerically by Runge-Kutta method. Due to the sensitivity of harmonics to thermal effects, gain improvement of third harmonic radiation is achieved by using ion-channel guiding technique and efficiency enhancement is applied by tapering the magnetic field of wiggler to optimize radiation. The bunching parameter of the electron beam is also studied. It is found that the growth of the magnitude of the bunching parameter that is caused by the ponderomotive wave stops before the saturation point of the radiation. This means that ponderomotive wave saturates at a shorter distance compared to the radiation.

Section: Numerical Resultsmentioning

confidence: 99%

“…Furthermore, it is a less expensive alternative to conventional focusing magnets. Because of these advantages, the technique of ionchannel focusing in the FEL has attracted a great deal of interest [27][28][29][30][31][32] and its use is a promising way to improve the system performance.…”

Section: Introductionmentioning

confidence: 99%

Efficiency enhancement of nonlinear odd harmonics in thermal free electron laser

Journal of Applied Physics

Maraghechi

2013

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“…By substituting fields of (2) into the Maxwell's equations, the dynamical equations which govern the evolution of the hth harmonic radiation are derived as follow (Freund and Antonsen 1996;Rouhani and Maraghechi 2010;Bazouband and Maraghechi 2012):…”

Section: Basic Equationsmentioning

confidence: 99%

“…is defined over an ensemble of electrons injected into the wiggler within one wave period. For this particle averages, a choice of 61 particles in Simpson technique was found to be adequate in the case of cold beam, which is increased to 16 × 16 = 256 particles in Gaussian quadrature technique for nonzero energy spread (Bazouband and Maraghechi 2012;2013).…”

Section: Basic Equationsmentioning

confidence: 99%

“…Harmonic radiation in FEL has been the most important method to achieve shorter wavelength with lower energy beam (Colson 1981;Freund et al 2000;Yu et al 2003;McNeil et al 2006;Bazouband and Maraghechi 2012;Giannessi et al 2012). In the compact FEL, which operates in long wavelengths, the low current/voltage electron beam is employed to reduce the size and cost of the required electron source.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Nonlinear third harmonic radiation in thermal free electron laser with modified wiggler

Maraghechi

2015

J. Plasma Phys.

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Simulation of free electron laser (FEL) with modified wiggler consisting of a conventional planar wiggler with third harmonic field component is presented. A set of self consistent nonlinear differential equations is derived and solved numerically by Runge–Kutta method. The optimum amplitudes of fundamental and third harmonic wiggler filed are obtained to increase the third harmonic radiation in comparison with conventional wiggler and also to have lower electron beam energy compared to conventional wiggler with the same wavelength. For the thermal effect the axial energy spread of electron beam, without any spread in the transverse velocity, is assumed. A peculiar region is found in which there is a sharp increase of the radiation amplitude. Thermal effect of the electron beam was found to be irregular in this peculiar region.

Compensation of thermal loss in free-electron laser with optimal tapering and pre-bunching

2020

Laser Part. Beams

AbstractIncreasing the output power of a long-wavelength free-electron laser (FEL), despite the destroying effects of beam energy spread, is studied using the optimal pre-bunching of the thermal electron beam along with the optimal tapering of the planar wiggler magnetic field. A set of self-consistent coupled nonlinear differential equations in three dimensional that describe the evolution of radiation and electron beam in the interaction zone are solved numerically by the Runge–Kutta method. The axial energy spread is considered and it degrades the FEL performance by reducing the saturation power and increasing the saturation length. To compensate these destroying effects, the optimum function or degree of electron beam pre-bunching and optimum parameters of wiggler tapering are found by the successive runs of the simulation code.