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Topic: Free electron laser

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In the News (Wed 19 Jun 19)

  Free electron model - Wikipedia, the free encyclopedia
The free electron model is a quantum model as opposed to the Drude model, which is classical.
The free electron model should be contrasted with the tight-binding model, which uses the opposite simplification of treating the electrons as tightly bound to the atomic cores.
As not all the forces on the electrons are taken into account the electrons have a effective mass that is larger than the free electron model predicts.
en.wikipedia.org /wiki/Free_electron   (394 words)

 Free electron laser - Wikipedia, the free encyclopedia
While an FEL laser beam shares the same optical properties as conventional lasers such as coherent radiation, the operation of an FEL is quite different.
Today, a free electron laser requires the use of an electron accelerator with its associated shielding, as accelerated electrons are a radiation hazard.
In a gyrotron or free electron laser the EM-wavelength is smaller than the electron beam and the electrons have to be manipulated.
en.wikipedia.org /wiki/Free_electron_laser   (1214 words)

 How a Free-Electron Laser Works   (Site not responding. Last check: 2007-10-30)
Vanderbilt's Mark-III free-electron laser is tunable from 2 to 10 microns (a micron is 1/1000th of a millimeter).
The FEL accelerates electrons to an energy of 40 million volts, injects them into a wiggler and the emitted laser beam is transported into the center's laboratories and operating rooms for use in experiments.
Electron accelerators are being designed for their specific FEL needs, and facilities similar to the Keck FEL Center at Vanderbilt are being set up so that researchers at other institutions can take advantage of this new source of intense light.
www.vanderbilt.edu /News/research/ravf96/howravf96.html   (435 words)

 Phase locked RF linac free electron laser - Patent 4748629
In the situations encountered prior to the invention of RF Linac Free Electron Lasers, this requirement amounted to requiring a laser type source or sources in order to produce a coherent beam, and in the case of multiple lasers required means of phase locking the various lasers together.
Typical PLRFFEL layout 10 includes a conventional wiggler laser arrangement 12 that produces a laser beam in the form of pulses that are reflected from convex mirror 14 to concave mirror 16 to expand the laser beam and act as a grazing telescope to enlarge the propagating beam after it emerges from the wiggler.
In operation, the beam produced at wiggler laser 12 is expanded by mirrors 14 and 16, reflected from flat mirror 18 to dividing means 20 which reflects a major portion to mirror 22, a minor portion to mirror 28 and a substantial portion to output 32.
www.freepatentsonline.com /4748629.html   (2082 words)

 Smith-purcell free electron laser and method of operating same patent invention
In one embodiment, the free electron laser operates on a mode at which the group velocity of the evanescent wave is substantially close to zero such that no optical cavity is required.
In another embodiment, the free electron laser operates on a backward wave oscillator mode at which the group velocity of the evanescent wave is negative, where the evanescent wave is output from one of the first end and the second end of the grating.
In one embodiment, the beam of electrons is characterized with a beam current and an electron velocity, the Smith-Purcell radiation is characterized with a range of wavelengths, and the evanescent wave is characterized with a phase velocity and a group velocity.
www.freshpatents.com /Smith-purcell-free-electron-laser-and-method-of-operating-same-dt20060323ptan20060062258.php   (1792 words)

 The Free Electron Laser - C.W. Roberson
The free electron laser (FEL) is a device that converts the energy of an electron beam to coherent radiation by passing it through a periodic magnetic field.
There advantages and recent development in electron sources, electron accelerators, and magnet technology have made the free electron laser a potential alternative source of coherent radiation across the ultraviolet, visible, infrared, and microwave regions of the electromagnetic spectrum.
Potential FEL applications are apparent in many different areas, including energy generation by using high-power microwave radiation to heat plasmas to thermonuclear fusion temperatures; missile defense by using high-power radiation in the optical wavelengths for SDI directed energy weapons applications; and in the laser separation of isotopes of uranium.
www.worldandi.com /specialreport/1989/july/Sa16034.htm   (292 words)

 Exploring News & Features - How the free-electron laser works   (Site not responding. Last check: 2007-10-30)
LASER is an acronym for light amplification by stimulated emission of radiation.
The free-electron laser (FEL) is an ideal instrument for charting the interactions of light and matter in many of the still unexplored regions of the electromagnetic spectrum.
The FEL is ideal for exploring the unknown regions in the spectrum because it is tunable over a broad range of the spectrum.
exploration.vanderbilt.edu /news/news_fel_works.htm   (756 words)

 Experiments   (Site not responding. Last check: 2007-10-30)
To achieve net energy exchange between the laser field and the electrons, a resonance condition must be satisfied so that the electron wiggle matches the period of the laser oscillation.
It is possible to obtain energy gains higher than the taper by controlling the amount of synchrotron oscillations occurring while the electrons are trapped within the laser field ponderomotive potential well inside the undulator.
3, which shows the electron energy-phase distribution exiting the accelerator undulator for a case where the laser intensity is near threshold.
www.bnl.gov /ATF/experiments/STELLA/Inverse-FreeElectronLaser.htm   (699 words)

 Jefferson Lab Free-Electron Laser Program
Extensions of the FEL to 250nm in the UV are planned.
The short pulses of electrons also produce hundreds of watts of broadband THz light, which is made available in a special user laboratory.
The FEL program is led by Fred Dylla under the auspices of the Laser Processing Consortium, a growing partnership of high-technology manufacturers, start-up companies, research universities, government, the Commonwealth of Virginia and the U.S. Navy.
www.jlab.org /FEL   (161 words)

 Exploring News & Features - How the free-electron laser works
The FEL, however, is not subject to this limitation because it produces laser light by sending bunches of electrons through a series of magnets in a vacuum.
The color of the laser beam can be varied in two ways: putting more power into the electron beam and changing the spacing between the magnets in the wiggler.
The Vanderbilt FEL is designed to produce a beam with a peak power of more than 10 Megawatts and an average power of 10 Watts.
www.vanderbilt.edu /exploration/news/news_fel_works.htm   (756 words)

 Free Electron Laser Group
The Free Electron Laser Group is engaged in a broad investigation of the physics and engineering of critical components of an advanced, accelerator-based coherent light source known as the free electron laser (FEL).
Electrons leave the cathode because of the photoemission effect: electrons absorb incident photons and gain sufficient energy to cross the barrier to vacuum.
In fact, nearly every stage of an electron beam's "journey" from its inception at the cathode to its acceleration and undulation through the wiggler are studied and modeled by members of the FEL group at Maryland and its research collaborators.
www.ireap.umd.edu /FEL   (494 words)

 FEL Pendulum Model
The energy released by the electron increases the laser field and consequently lowers the minimum further.
The position of the electron is determined by the pondermotive (or electron) phase,
The pendulum FEL model is valid for both weak or strong optical fields and for high or low gain.
webphysics.davidson.edu /Applets/FELPart/FelOde.html   (679 words)

 Duke Ultraviolet Free-Electron Laser Sets New World Record
Free-electron lasers are like no others in that they make laser light by perturbing beams of "free"electrons that have been liberated from their normal bondage to atoms.
The Russian laser was moved to Duke in May 1995 as part of a collaborative agreement between BINP and FELL to develop advanced ultraviolet free-electron lasers.
After the laser resumes operations in about two months, the scientists hope they will be able to provide ultraviolet light for experiments in eye surgery, neurosurgery and cancer research, as well as continuing work in microscopy.
www.eurekalert.org /pub_releases/1998-04/DU-DUFL-230498.php   (654 words)

 New Amplification Record Set By Free Electron Laser
The free electron laser at DESY produces ultraviolet laser light with wavelengths between 80 and 180 nanometers (one millionth of a millimeter).
There the intensive laser light is produced using a new principle: electrons are brought to high energies in a superconducting accelerator, then traverse on a slalom-like course a special arrangement of magnets and emit laser-like bundles of radiation.
At the SASE free electron laser at DESY, it has been shown for the first time that the self-amplifying effect indeed does lead to the theoretically calculated amplification by a factor of ten million in the ultraviolet regime.
unisci.com /stories/20013/0920015.htm   (702 words)

 Free Electron Laser - Forschungszentrum Rossendorf
FELBE is an acronym for the free-electron laser (FEL) at the Electron Linear accelerator with high Brilliance and Low Emittance (ELBE) located at the Forschungszentrum Rossendorf in Dresden, Germany.
The electron beam is guided to several laboratories where secondary beams (particle and electromagnetic) are generated (→ details).
A spectacular future perspective is the connection of the FEL with the pulsed high-magnetic field laboratory (2007).
www.fz-rossendorf.de /pls/robis/Cms?pNid=471   (365 words)

 Free Electron Laser Reaches 10 KW
Conventional lasers are limited in the wavelength of light they emit by the source of the electrons (such as a gas or crystal) used within the laser.
In the FEL, electrons are stripped from their atoms and then whipped up to high energies by a linear accelerator.
As in a conventional laser, the photons are bounced between two mirrors and then emitted as a coherent beam of light.
www.spacedaily.com /news/laser-04q.html   (685 words)

 UCLA PBPL - Free-Electron Laser
A free-electron laser (FEL) [1] transforms the kinetic energy of a relativistic electron beam, produced by a particle accelerator like a microtron, storage ring, or radio frequency (RF) linac, into electromagnetic (EM) radiation.
One can either transfer energy from the beam to the wave, in which case the device is an FEL, or from the wave to the beam, in which case it is an inverse FEL (IFEL) [3].
FELs originate in the work carried out in the 1950s and 1960s on the generation of coherent em radiation from electron beams in the microwave region [2,9].
pbpl.physics.ucla.edu /Research/Theory/Free-Electron_Laser   (927 words)

 Latest Free-Electron Laser Will Reach X-Ray Range
The components of a next-generation laser that could allow three-dimensional holographic images of objects as small as molecules and events as rapid as chemical reactions are now being tested in preparation for installation at the Duke Free-Electron Laser Laboratory (FELL).
FELs are unique in that they produce laser light by perturbing beams of electrons freed of their normal bondage to atoms.
This mechanism allows such lasers to be tuned to emit laser beams at a variety of different wavelengths, a flexibility that makes them extremely useful in research.
www.dukenews.duke.edu /2003/01/ok-5.html   (997 words)

 Argonne sets world record for shortest wavelength ever from free-electron laser
A further significant feature of this free-electron laser is that by merely changing the electron beam energy, the light is continuously tunable over a broad range of wavelengths, thus breaking additional barriers to traditional lasers.
With further development, free-electron lasers of this sort promise to provide extremely bright, laser-like X-ray beams with ultrashort pulse durations that will enable scientists to study the properties and structures of materials in far greater detail and in far less time than is possible today.
The ability to study "warm, dense matter," a state between one in which all the electrons surrounding a collection of atoms are highly excited and one in which all the electrons and atoms have become so excited that the electrons are stripped from the atoms and the whole collection becomes a hot plasma.
www.anl.gov /Media_Center/Frontiers/2002/b2excell.html   (1067 words)

 FZR Free Electron Laser
We investigated the electron beam transport and the single pass gain in this undulator as a function of electron bunch parameters and undulator strength which is adjusted with the width of the gap between the two arrays of magnets.
To restore the synchronism, and thereby the FEL mechanism, one should either tune the length of the drift gap or only the pathlength of the electrons in the gap with a chicane.
When electrons are injected repeatedly, while the radiation remains captured between the mirrors, the amplitude of the whole wave train grows, provided that the new electrons are injected at exactly the right time.
www.pulsar.nl /projects/fzr   (1002 words)

 Free-electron laser targets fat
Laser therapies based on the new research could treat a variety of health conditions, including severe acne, atherosclerotic plaque, and unwanted cellulite.
Based on a fat absorption spectrum, tissue was exposed to a range of wavelengths of infrared laser light (800-2600 nanometers) using the Free-Electron Laser facility at Jefferson Lab.
Anderson says this study was made possible by the physics knowledge that built the Free-Electron Laser (FEL) at Jefferson Lab and a grant from the Department of Defense for the exploration of medical uses for FELs.
www.eurekalert.org /pub_releases/2006-04/djna-flt040606.php   (952 words)

 Free-Electron Laser Program
The laser is on a lower floor, with laboratories located on an upper level.
Electrons are released from the source at the lower left, and are accelerated in a superconducting linear accelerator (linac).
This wiggler causes the electrons to oscillate and emit light which is captured in the cavity, and used to induce new electrons to emit even more light.
www.jlab.org /FEL/feldescrip.html   (263 words)

 Duke FEL Laboratory: Lightsources
A free-electron laser (FEL) is an accelerator based light source capable of generating coherent, high power radiation with optical properties characteristic of convential lasers such as high spatial coherence and a near diffraction limited radiation beam.
While a convential laser uses bound atomic or molecular states as its lasing medium, an FEL uses a relativistic electron beam, thus the term "free-electron".
The characteristics of the emitted light are determined by the electron beam energy and pulse structure, and the magnetic field characteristics of the undulator.
www.fel.duke.edu /lightsources   (245 words)

 Tabletop Free Electron Laser Tunes Across Far IR
To create the FEL, Walsh and his team modified a SEM so that it shoots electrons at velocities near the speed of light across a grooved metal plate.
Because multiple electrons cross the grating simultaneously, the peaks of the waves reinforce each other, producing a bright, coherent beam of radiation in the far-infrared frequency range.
For his achievement, Walsh was awarded the 1998 Free Electron Laser Award by his colleagues, an annual award that recognizes the top FEL researcher in the world.
www.photonicsonline.com /content/news/article.asp?docid={596044b9-f514-11d2-a405-00c04f4f7c39}&VNETCOOKIE=NO   (1187 words)

 Encyclopedia of Laser Physics and Technology - X-ray lasers, free electron laser
An X-ray laser is a laser device which can emit in the spectral region of X-rays, i.e., with wavelengths of only a few nanometers.
Free electron lasers consist basically of an undulator through which very high energy electrons are sent, and (usually) a laser cavity.
As it is difficult to construct a low-loss cavity for such short wavelengths, X-ray 'lasers' are in most cases (particularly for shorter wavelengths) built without a cavity and actually operate as ASE sources (superluminescent sources).
www.rp-photonics.com /x_ray_lasers.html   (264 words)

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