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Cerenkov Radiation

06/15/2013 2:03 PM

Can someone provide a simple explanation of Cerenkov Radiation for me? I have seen it once in a used fuel element storage pool while working at Argonne National Lab--a beautiful light blue in color. I looked at Wikipedia, but my mind doesn't want to "get around" the subject. Thank you..

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#1

Re: Cerenkov Radiation

06/15/2013 3:29 PM

The speed of light in a vacuum (c) is an absolute maximum velocity. In media other than a vacuum the speed of light can be considerably slower. When anything traveling slower than c but faster than the speed of light of the media it is traveling through then photons (Cerenkov radiation) are generated until the particles are at or below the light velocity for that media.

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#2

Re: Cerenkov Radiation

06/15/2013 4:57 PM

It's like a continuous sonic boom, but between light and energetic particles....

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#3

Re: Cerenkov Radiation

06/15/2013 5:40 PM

Another analogy is that of a wake made by a boat traveling faster than the wave speed in water.

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#4

Re: Cerenkov Radiation

06/15/2013 10:55 PM

Any matter's Epsilon (permittivity), Mu(permeability) and the speed of light are determined as a sort of ratio of the others. Any attempt to separate them out have failed.

Since Epsilon is very much a frequency dependent factor, n (refraction) is a ratio of it for visible light frequencies.

Now to Cherenkov. When an energetic photon from a hot fuel rod enters the high n water surrounding it, It is initially moving than faster than light in that material. That is not permissible. Hence, upon interaction with the local atoms, it starts shedding energy until it is at the speed of light defined in this matter. The shed energy is, what you see in the nice blue light.

This sounds pedantic, but particle physics sounds like that frequently.

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#5
In reply to #4

Re: Cerenkov Radiation

06/16/2013 1:57 AM

"When an energetic photon from a hot fuel rod enters the high n water surrounding it, It is initially moving than faster than light in that material. That is not permissible."

Not photons, but rather charged particles leaving the rods. Photons, having no rest mass and slowing down instantly in glass or water, do not create Cerenkov radiation as far as I know.

-J

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#6

Re: Cerenkov Radiation

06/16/2013 6:21 AM

Yes, I misspoke.

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#7

Re: Cerenkov Radiation

06/16/2013 7:21 PM

Thanks for the several replies; they help a lot.

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#8
In reply to #2

Re: Cerenkov Radiation

06/17/2013 9:21 AM

good answer, and good photo!

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#9
In reply to #2

Re: Cerenkov Radiation

06/18/2013 4:59 PM

Could we call it a photonic boom?

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#10

Re: Cerenkov Radiation

06/19/2013 8:00 AM

This shade of blue is cosmically beautiful...and also unique. The first time I saw this, I was mesmerised for about 30 minutes!

No.'s 4 & 5 gave your explanation, but I add that the colour itself is probably dependent on the high purity of the water. Impure or mineralised water may result in a different colour being observed.

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#11
In reply to #10

Re: Cerenkov Radiation

06/29/2013 6:29 PM

Cerenkov is always blue, the cerenkov detectors that we design have to be sensitive in the blue to UV wavelengths.

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#12
In reply to #11

Re: Cerenkov Radiation

07/01/2013 3:05 AM

Apologies.....I didn't express it very well...I meant a different shade of blue.

The shade of 'Cerenkov' blue is (in my experience anyway) quite unique.

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#13
In reply to #11

Re: Cerenkov Radiation

12/13/2013 1:43 PM

An explanation for the origin of the blue color:

http://reactor.mst.edu/cerenkov/

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#14
In reply to #13

Re: Cerenkov Radiation

12/17/2013 3:44 AM

Nice!

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