Beam Creation
To create a FEL, a beam of electrons is accelerated to almost the speed of light. The beam passes through the FEL oscillator, a periodic transverse magnetic field produced by an arrangement of magnets with alternating poles within an optical cavity along the beam path. This array of magnets is sometimes called an undulator, or a "wiggler", because it forces the electrons in the beam to follow a sinusoidal path. The acceleration of the electrons along this path results in the release of photons (synchrotron radiation). Since the electron motion is in phase with the field of the light already emitted, the fields add together coherently. Whereas conventional undulators would cause the electrons to radiate independently, instabilities in the electron beam resulting from the interactions of the oscillations of electrons in the undulators and the radiation they emit leads to a bunching of the electrons, which continue to radiate in phase with each other. The wavelength of the light emitted can be readily tuned by adjusting the energy of the electron beam or the magnetic field strength of the undulators.
Read more about this topic: Free-electron Laser
Famous quotes containing the words beam and/or creation:
“Why beholdest thou the mote that is in thy brother’s eye, but considerest not the beam that is in thine own eye?”
—Bible: New Testament Jesus, in Matthew, 7:3.
From the Sermon on the Mount.
“The human spirit is itself the most wonderful fairy tale that can possibly be. What a magnificent world lies enclosed within our bosoms! No solar orbit hems it in, the inexhaustible wealth of the total visible creation is outweighed by its riches!”
—E.T.A.W. (Ernst Theodor Amadeus Wilhelm)