Q about laser and maser radiation and plasma...

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Sven Andersson
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Q about laser and maser radiation and plasma...

Post by Sven Andersson » Tue Oct 03, 2017 4:23 pm

What will happen if you shine laser (visible or UV or IR) radiation or maser radiation through a plasma? Will the radiation be scattered by free electrons and be lost and squandered?

And how will the charged particles respond to the radiation? Will they begin to oscillate?

Let's say you set up an experiment with a standing wave maser or laser radiation in a plasma, how will the random thermal movement of the particles be affected?

Sven

Andrew Seltzman
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Re: Q about laser and maser radiation and plasma...

Post by Andrew Seltzman » Tue Oct 03, 2017 5:32 pm

Scattering by electrons:
Yes, this process is called thomson scattering, it is used as a plasma temperature diagnostic.
https://en.wikipedia.org/wiki/Thomson_scattering

Absorption:
An electromagnetic wave (typically radio frequency) can be resonantly absorbed, and transfer it's energy to the plasma.
Andrew Seltzman
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Sven Andersson
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Re: Q about laser and maser radiation and plasma...

Post by Sven Andersson » Wed Oct 04, 2017 3:50 pm

Sven Andersson wrote:What will happen if you shine laser (visible or UV or IR) radiation or maser radiation through a plasma? Will the radiation be scattered by free electrons and be lost and squandered?
I ask these questions because I want to find out how laser radiation will affect the (relative) movement of pairs of charged particles in a plasma, and if this can be used to boost fusion.

Let's say you have polarized laser or maser radiation going through a plasma. Then the charged particle e.g. deuterons will begin to oscillate. Let's say a pair of them designated A and B, that have no movement relative to the EM wave or to one another, are oriented as in the picture below.
1987427.jpg
I have two questions:

1. A and B must be oscillating out of phase; now, is there a tendency for them to end up exactly one (or 2,3,4...) wavelength apart (for example at the spots marked by two arrows), oscillating in phase? Or perhaps in the same place?

2. Let's say A and B have movement relative to one another, either receding or approaching one another; is there a tendency for that movement to decrease? I can't get it out of my mind the suspicion that this will happen due to coupled oscillations.

Sven

ian_krase
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Re: Q about laser and maser radiation and plasma...

Post by ian_krase » Thu Oct 05, 2017 1:39 am

Kinda sounds like you're describing an RF ion source to me.

John Myers
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Re: Q about laser and maser radiation and plasma...

Post by John Myers » Thu Oct 05, 2017 7:13 am

Based on the picture A and B are still in phase but have a different polarity.
If a polarized maser/laser had the same polarity as A then it would primarily effect the amplitude of A's with the same wavelength(or harmonics of).

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Dennis P Brown
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Re: Q about laser and maser radiation and plasma...

Post by Dennis P Brown » Thu Oct 05, 2017 12:27 pm

Getting a strong interaction between a plasma and a laser requires either a very high powered laser or a rather dense plasma or both (best situation.) The average fusor plasma and using any laser one can generally obtain will have only a very tiny interaction rate that will not be significant - from the point of view of any interesting physics for fusion. While this is now of great interest in ICF where the laser beams are 10^14-16 jouls/cm^2 and interacting with highly ionized plasma's (but even here, the deuterons are irrelevant for the process.) This is of interest because this type of interaction is parasitic for the beam-target coupling. An interesting topic but rather hard to study but of no use for plasma (i.e. magnetic or electro-static) fusion.

Deuterons are not going to couple to any significant extent with a laser beam in any manner that affects the deuteron fusion; yes, Rayleigh scattering can occur for the photons with electrons (more strongly) and protons (weak). I think you are confusing the effects of a laser on electrons (free) with the very massive deuterons (which means they will not generally interact via energy coupling to the proton-neutron ions); the effects between these two types of particles is vastly different. Protons/neutrons/nuclei interaction with any photon is insignificant unless the photons have energies on the order of x-ray/gamma ray. As for radio-frequency plasma effects, this subject is well covered by others and is easy to search.

Sven Andersson
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Re: Q about laser and maser radiation and plasma...

Post by Sven Andersson » Thu Oct 05, 2017 5:08 pm

Sven Andersson wrote:1. A and B must be oscillating out of phase; now, is there a tendency for them to end up exactly one (or 2,3,4...) wavelength apart (for example at the spots marked by two arrows), oscillating in phase? Or perhaps in the same place?

2. Let's say A and B have movement relative to one another, either receding or approaching one another; is there a tendency for that movement to decrease? I can't get it out of my mind the suspicion that this will happen due to coupled oscillations.
What I'm really after is what will happen to, say a deuteron, that is oscillating in e.g. a polarized laser beam, if at the same time another particle next to it transfers or sucks up some energy from it, through coupled oscillations? The deuteron will then be oscillating either too fast or too slow. Will there then be a force working on it, to drag it along the laser beam or push it backwards, so to speak?

What mathematics and physics can be used to solve such problems?

Sven

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Dennis P Brown
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Re: Q about laser and maser radiation and plasma...

Post by Dennis P Brown » Thu Oct 05, 2017 5:32 pm

Again, a laser beam will not measurably cause a deuteron to oscillate (other effects would swamp out any tiny occurrence); you are ether mis-stating your question or you are determined to make something occur that the physics does not support. One can cause a deuterium molecule to oscillate with lower energy photons that lasers or other sources can provide. Deuterium nuclei will not significantly oscillate in any field a laser can create. As for energy sharing - that is via simple collisional processes in a fusor. I do not think you have read enough on how a fusor works and how fusion occurs.

Sven Andersson
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Re: Q about laser and maser radiation and plasma...

Post by Sven Andersson » Wed Oct 11, 2017 3:30 pm

If anyone has any knowledge (e.g. tips on books or articles to read) on how to theoretically solve the problems I describe in this thread (or similar problems) and the other thread I have posted, please respond!

Sven

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Re: Q about laser and maser radiation and plasma...

Post by John Myers » Sun Oct 15, 2017 1:15 am

These two books may be helpful...
viewtopic.php?f=21&t=8164 and Charged Particle Beams.

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