Questions tagged [free-electron-lasers]
14 questions
35
votes
5 answers
Do free-electron lasers actually lase?
Free-electron lasers are devices which use the motion of highly energetic electron beams to produce bright, coherent radiation in the x-ray regime. More specifically, they start with a high-energy electron beam and feed it into an undulator, which…
Emilio Pisanty
- 137,480
2
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2 answers
What is the difference between an undulator and a free-electron laser (FEL)?
I am very confused by the graphic below: In particular, why are undulators and FEL separated?
Furthermore, I do not quite understand how the intensity values come to be:
Wiggler: Every electron radiates at any pole ($N_e \cdot N_p$)
Undulator: The…
Fabian Schn.
- 155
2
votes
0 answers
How does self-amplified spontaneous emission (SASE) work?
Due to the new laser in Hamburg, the XFEL, the following question arised: How does self-amplified spontaneous emission (SASE) work?
There is an official article here http://www.xfel.eu/overview/how_does_it_work/ but unfortunately it's not sufficient…
Ben
- 1,557
2
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1 answer
free electron laser. Reference?
Where can I find a comparison graph of the peak power of free electron lasers and synchrotrons ?
Anonymous
- 1,057
1
vote
0 answers
Microbunching in Free Electron Lasers
I'm currently trying to understand how microbunching develops in free electron lasers (FELs). As I understand it, electrons oscillate transversely as they pass through the undulator, emitting synchrotron radiation in the process. This radiation can…
Jonas
- 21
1
vote
1 answer
What is meant by "low-lying" electronic states?
In the context of electronic structure and spectroscopy, the term "low-lying electronic states" is quite common but it really isn't defined anywhere. All google search results lead to research papers that just use the term. So my question is, what…
PestoPotato
- 13
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1
vote
0 answers
Rhodium based gamma-laser
Has anyone considered using the excited meta-state of Rh 102 to create a gamma-ray laser?. I see an advantage in favor of using Rh 102m extracted from nuclear waste over Hf 178m2.
While Rh 102m has a reasonably long half-life of 3.7 years, this is…
Donkey
- 21
1
vote
2 answers
Why is the opening angle of synchrotron radiation less than $1/\gamma$?
I am currently studying free-electron laser which accelerate electrons and use undulators to create synchrotron radiation. In a variety of graphics and diagrams I see an opening angle of $\pm 1/\gamma$ for the radiation.
Where does this value come…
Fabian Schn.
- 155
0
votes
1 answer
When a laser pulse rate is stated, does that include the time that it is off? If pulse rate is 1,000 per second, is it on for half a millisecond?
Sorry if this seems a stupid question to some, but I am having trouble finding a consistent answer....
The European XFEL hard X-ray headline proudly states that it is currently the fastest of its kind in the world, for example, at '27,000 pulses per…
Kurt Hikes
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1 answer
Does a low-gain free electron laser (FEL) emit coherent radiation?
For the low-gain free electron laser (FEL), an external field is injected into an undulator alongside an electron bunch. Due to phase slippage (because the light is faster than the electrons) the electron and light field are always in resonance.…
Liberty
- 77
0
votes
2 answers
Laser book for physics GRE
The recent physics GRE exams have some questions on lasers. Does anyone know of a good book which goes briefly through different types of lasers?
ben tenyson
- 171
0
votes
1 answer
The physics behind European XFEL
I tried to find detailed data at the official site
and learned that the linear accelerator is 1.7 Km long, the energy of the electrons is 17.5 GeV (35000$\times$ the electron rest energy), and the wavelength of the radiation is 0.07 to 4.5 nm.
[If…
user157860
- 691
0
votes
1 answer
What makes the European XFEL the "fastest laser in the world"?
I'm working in Hamburg so listening this morning to the local radio channels, all had been reporting about the "greeting call" to DESY by different organizations pointing with their lasers to the European XFEL for getting public attention to…
Zaibis
- 1,299
0
votes
2 answers
A question regarding pump-probe processes
As the following figure illustrated,the pump-probe processes contain mainly two steps:
Pump pulse drives the sample out of equilibrium (red line);
Time evolution measured by subsequent probe pulses;
I have some questions for this pump-probe…
Jack
- 1,847