|WikiProject Physics||(Rated Start-class, Mid-importance)|
|WikiProject Technology||(Rated C-class)|
- 1 Images
- 2 The name of an X-ray device
- 3 Very Dense Verbage
- 4 Last paragraph of FEL creation
- 5 Outside Links
- 6 Northrop Grumman hits Weapons grade FEL
- 7 tuning / noisy startup problem
- 8 Vs. Undulator?
- 9 Micrometres? I doubt it.
- 10 Explanation wrong
- 11 Analog of Population Inversion?
- 12 Navy FEL breakthrough
- 13 Sources
- 14 Some unclarity
- 15 SASE - Self amplified SPONTANEOUS emission the article is wrong here
- 16 Wrapping up the beam creation, large facility, mirror and seeded section
I've replaced two images with the image from the german article. Feel free to re-add the others if you think otherwise. IMHO in FEL1.jpg the electron beam doesn't wiggle at all and in FEL2.jpg in the wrong plane. --Pjacobi 12:25, 2005 Mar 6 (UTC)
- Yup, better picture. It's just kinda too small though. Any chance you've got something about 200-400px big? Cal 1234 15:52, Mar 6, 2005 (UTC)
The name of an X-ray device
Since a "microwave amplification by stimulated emission of radiation" device is called a maser and a "light amplification by stimulated emission of radiation" device is called laser, an "X-ray amplification by stimulated emission of radiation" device should most properly be called either a xaser, or since masers were first, an X-ray maser? Besides xaser being hard to pronounce, laser is a much more common term than maser ever was, so I imagine that it will stay "X-ray laser". --David R. Ingham 23:28, 18 July 2005 (UTC)
- An FEL does not amplify the x-rays (or whatever kind of radiation) by stimulated emission. See self-amplified spontaneous emission (SASE). I believe FEL has the word laser in it because free electrons create laser alike radiation, i.e. monochromatic, directional (thereby intense) and coherent. FEL can produce light in various wavelength regimes. Only x-ray free electron laser are commonly abbreviated as XFEL. I've never heard 'xaser' and I think 'x-ray laser' is misleading because it is not stimulated emission that amplifies the radiation. I propose to use FEL or XFEL instead! --Maderthaner (talk) 02:17, 13 November 2014 (UTC)
Very Dense Verbage
I have a doctorate in biophysics, yet I could not understand discussion of the XFEL. Sorry to whoever worte it. :) Can someone who understands the basic underlying theory rewrite this section in the style of the "News/Focus" section of the journal Science. An example: the current versions says "down to a wavelength of 1.5 Ångstroms." How good is that? How "hard" are x-rays of that wavelength? The journal Science says, "These 'hard' x-ray wavelengths—down to 0.1 nanometers—promise to reveal the structure of proteins that have eluded other techniques and nanometer-scale features inmeterials.", This is an excellent example of the style I would like to see here. Can someone who understands the technology please describe how XFEL are built and generate x-rays? Nwbeeson 14:53, 20 November 2006 (UTC)
Last paragraph of FEL creation
It seems to me that the word "so" is used too many times in this paragraph, it doesn't read well.
"Depending on the position along the undulator the oscillation of an electrons is in phase or not in phase with this radiation. So the light either tries to accelerate or decelerate this electrons. So it gains or loses kinetic energy, so it moves faster or slower along the undulator. So the electrons form bunches. Now they are synchronized and will in turn emit synchronized (that is coherent) radiation."
I would recommend replacing it with something like:
"Depending on the position along the undulator the oscillation of an electrons is in phase or not in phase with this radiation. The light either tries to accelerate or decelerate this electrons. It thereby gains or loses kinetic energy, so it moves faster or slower along the undulator. This causes the electrons to form bunches. Now they are synchronized, and will in turn emit synchronized (that is coherent) radiation."
--Patrick--220.127.116.11 23:39, 8 December 2006 (UTC)
Northrop Grumman hits Weapons grade FEL
http://blog.wired.com/defense/2008/09/weapons-grade-l.html —Preceding unsigned comment added by 18.104.22.168 (talk) 13:54, 25 March 2009 (UTC)
tuning / noisy startup problem
can you "tune" SASE FEL by slowly changing the energy of the electron beam? Or would the beam (its coherency) have to break down inbetween? because the beam is faster than the electrons, and would interact with electrons that still have the old energy. would the beam just get a bit "dimmer" while tuning? --Maxus96 (talk) 02:06, 27 March 2010 (UTC)
Micrometres? I doubt it.
From the article:
- Research by Dr. Glenn Edwards and colleagues at Vanderbilt University's FEL Center in 1994 found that soft tissues like skin, cornea, and brain tissue could be cut, or ablated, using FEL wavelengths around 6.45 micrometres with minimal collateral damage to adjacent tissue.
Considering 6.45 micrometres would be 6450 nanometres, in the far infrared, it would less cleanly ablate and more horrifically burn. It would be super if I could actually investigate the reference, but like most ivory tower sources, I cannot. Whatever. Bad science is bad science, and I will boldly change it to nanometres, since that would put the value directly in the soft (non-penetrating) X-ray range that I am sure is being discussed.
For the record, it seems that the text was originally added as "microns", then someone (reasonably) changed it to micrometres.
- It turns out I was wrong.
- I did not originally search very deeply, because, usually, the best case scenario is "purchase a copy of this article for $30", and the worst case scenario is nothing at all. This time, however, someone wrote up a story accessible to the unwashed masses. The linked article clearly states that the laser is infrared, although I admit that I must not understand the physics behind its effect on tissue.
- I will change the text back to micrometres. I will also add the linked article as another source, so I can clarify that the laser in question is indeed infrared.
- I will also cite to the best of my ability the statement about the "Raman shifted system pumped by an Alexandrite laser", and request citation on the more general statement about "several efforts to build small, clinical lasers tunable in the 6 to 7 micrometre range".
- Thank you for your efforts. Yes you have to bear in mind this is laser technology, so it is the highly collimated and coherent beam which enables the cutting action. The infrared wavelength is necessary because it more easily absorbed than other wavelengths. Typically, the smaller the wavelength the more transparent matter is. If you have problems accessing full text articles, there is a wikiproject WP:LIBRARY in which participating users can provide other users with access to specific articles / textbook etc. Polyamorph (talk) 19:54, 6 November 2010 (UTC)
- The description "Beam creation" is incomplete and requires verification an I agree the entire article needs work, but I wouldn't go so far as to say it is wrong. Insertion devices are indeed used in free electron laser devices. Polyamorph (talk) 20:12, 6 November 2010 (UTC)
Analog of Population Inversion?
"Military Tech: Breakthrough Laser Could Revolutionize Navy's Weaponry" Published January 20, 2011
Hope this helps, Charles Edwin Shipp (talk) 00:30, 21 January 2011 (UTC)
Is there a reason that the article does not cite the relevant papers for things such as the history behind FELs for the introduction, but rather lists them as further reading? --Dlfreese (talk) 07:15, 31 May 2012 (UTC)
The article does not make it clear how a Free-electron laser differs from a synchrotron light source. Both use insertion devices (undulator or wiggler, and on that subject it is not made clear what the difference between those are either) but clearly there must be a difference, right? From what I understand, an FEL uses some sort of modulation to "bunch" electrons in packets such that the distance between each bunch causes all the emitted synchrotron radiation photons to be in phase. Could someone who knows more on this subject clear this up? In any case, the difference should be made more clear, as the article is incredibly vague in its current state.
- The difference between FEL and SLS is that a FEL has a resonant cavity; the light is reflected between mirrors and is used to stimulate emission in the next bunch of electrons that passes through the undulator, leading to light amplification. Synchrotron radiation [light from SLS] arises from a single bunch of electrons passing once through an undulator. (For XFELs this is not the case, but that is already explained in that section.) VictorClaessen (talk) 15:00, 16 August 2017 (UTC)
SASE - Self amplified SPONTANEOUS emission the article is wrong here
Please someone correct that mistake, there is no stimulation, amplification essentially starts from noise! I tried to correct this already but my changes have been undone! English Wikipedia is the first search hit and wrong, great!
E. Saldin, E. Schneidmiller, and M. Yurkov, "The Physics of Free Electron Lasers" (Springer, 2000) (page 10 e.g.)
- I did change this. I have to say, this section of the article could be improved. --Maderthaner (talk) 02:23, 13 November 2014 (UTC)
Wrapping up the beam creation, large facility, mirror and seeded section
I propose to restructure the beam creation part of the article. I have the feeling that the first couple sections are all talking about this but not really to the point. I noticed often that the SASE process was explained in a dubious way and also seeding/self-seeding could be brought under this section. There is also multiple ways of creation a FEL seeded beam, e.g. self-seeding.--Maderthaner (talk) 02:33, 13 November 2014 (UTC)
- Science, vol 314 (5800), p. 751, 2006