# If you could look at the LHC beam, what would you see?

Kind of a weird question compared to what I normally ask on here, but I've been wondering about this for a while.

Does the LHC beam generate any photons within the visible light spectrum? Assuming the beam was traveling through air instead of a vacuum, would it interact with the nitrogen or oxygen to generate visible light?

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Does the LHC beam generate any photons within the visible light spectrum?

The LHC circulates in vacuum, with very few interactions with the rare left over atoms and molecules. It produces electromagnetic radiation, synchrotron radiation at the circular parts of the trajectory, as it bends. At 5.5 eV it is in the x-ray part of the spectrum, not the visible.

Assuming the beam was traveling through air instead of a vacuum, would it interact with the nitrogen or oxygen to generate visible light?

Yes, in a transparent medium there would be Cerenkov radiation, part of which is in the visible light. This is used for particle detection.

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I think this wiki article (Beware: this is a bit gruesome if you're squeamish) on Anatoli Bugorski, who suffered a dreadful accident at the Soviet U-70 collider, might help answer your questions. A proton beam passed through his head.

He apparently saw a flash of light brighter than a thousand suns, but lived to tell the tale.

As for the physics of what Burgorski saw, I guess it was synchrotron radiation from the accelerating protons. The U-70 operated at energies of $70$ GeV; the LHC in its first phase operated at $7$ TeV $= 100 \times 70$ GeV. Maybe you can do the synchrotron radiation calculation of LHC versus U-70 to see how much brighter the flash would be at the LHC.

EDIT: It's not clear whether the flash Burgorski saw was the result of light in his eyes, a psychological reaction of fright, or a neurological reaction from the protons stimulating his brain.

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with the earlier accelerators there were physicist centering the beam by he Cerenkov radiation in their eyes. I have heard that as the reason they got cancer on the retina. when the PS (30 GeV)beam at CERN was dumped at the beam dump, you could hear the bang. – anna v Apr 28 '13 at 12:08
I bet Bugorski now has superpowers. – twistor59 Apr 28 '13 at 12:54
It would be highly unwise to "look" into the LHC beam. There is a wonderful document that describes the energy release in the LHC's beam dump... which is made of carbon. Body tissue is sufficiently similar to that in terms of density and nuclear composition. One can therefor expect, that the temperature rise would be similar to that in the beam dump. Even with a well timed deflection pattern, which spreads out the energy release, the carbon absorber heats up by 1250 degrees Celsius. Needless to say, under the same conditions the observer's head would, quite literally, explode. – CuriousOne Aug 11 '14 at 7:23