Spontaneous Emission in a Free-Electron Laser
Spontaneous Emission in a Free-Electron Laser
This Demonstration shows an electron bunch entering an undulator magnet (represented by a sinusoid with period ). The electrons experience a Lorentz force (assuming the magnetic field is directed vertically) and execute transverse oscillations in the horizontal plane. The emission process is characterized by antenna lobe emission, which is more intense when the acceleration is greater. The process can be described either in the laboratory or in the electron rest frame. In the latter case, the electrons "see" the undulator field as an incoming electromagnetic wave with a wavelength that is linked to the undulator Lorentz contracted period.
λ
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As a further option, a moving packet has been included with the associated debunching when propagating inside the undulator.