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"What happens if I put my hand in the LHC beam"?

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The (dreaded) "Man in Pub" asks:  "What happens if I put my hand in the LHC beam"? Perhaps now an old question? Common knowledge? Failure to answer proves "Scientists don't know everything" etc.  :D


New one on me. Interesting (reasonable) that many on the video did not have an immediate answer?

Despite indifferent Google translation, you might get some real notions from a more original source?

http://www.eco-pravda.ru/page.php?al=bugorsky_casus  (Beware: A bit "graphic"!):  :o

I do remember people dangling things (not body parts!) in secondary beams (Don't tell 'em, Pike!) - But that was quite a while ago and beam energies... intensities anyway, have increased. Physical damage to fixed targets in the path of primary Proton Beams was well enough known / documented even then.

An interesting calculation for the reader? Overall not a great thing to try in practice! :p

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An interesting example of how (some) physicists think. Do some back-of-envelope calculations and come up with several widely different answers, when all along there's a living example (Anatoli Bugorski) of someone who effectively did the experiment, albeit at far lower energy. I think the conclusion is that the LHC would make a hole in your hand. Great links - thanks for sharing.

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Beautifully understated: "was involved in an accident with a particle accelerator" :)

Makes it sound like it dropped on his foot or something.

"Oh, sorry chaps.  I've just spilt vodka in the particle accelerator."


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Which sort of time scale would we be talking? Milliseconds? Seconds? Minutes?

The LHC (colliders in general) have continuously circulating beams of stored particle bunches. If you could access them (In practice, hopefully you can't!) The vacuum in the ring would be destroyed etc. The whole contents of the LHC would impact on the "target"... or elsewhere in VERY short time scale. Basically on a time scale of one "orbit" at the speed of light?  :eek:

In previous generations of *fixed target* experiments, protons were accelerated, in the main "ring", then extracted (by kicker magnets) at peak energy into various "beam lines" over (say) a couple of seconds. The beam could be shared between several targets / experiments switched on and off etc. System were fairly dynamic - Bit like a series of railway sidings with "points", "buffers" etc. Experimental groups can often control local "beam steering" too.   :)

Acceleration / Extraction takes a "cycle" time of a few seconds? I imagine the unfortunate Russian put his head into (what he thought!) an "inactive" beam line. The main ring was in acceleration, then went into extraction mode? Settings changed? Magnets failed? Safety interlocks failed? Who knows?  :o

I found this rather long (pdf format) CERN machine physics lecture. Dating from early days, around page 25(!), you can see some of their controlled experiments of dumping the total contents of the test beams into a copper target etc. Basically, it seems the beam would indeed drill a HOLE through 2m lengths of copper, vaporising the first part and melting deep into the whole length. Much more spectacular than I had thought frankly.  :p


Some specifications on the standard beam dumps too - These used to empty the LHC beam at the end of normal runs. Large lumps of carbon, surrounded by cooling / concrete radiation shielding... ;)

Edited by Macavity
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Thanks for the link Macavity. Amongst other things, p.14 says that the energy stored in the beam is equivalent to 90kg of TNT.  The magnets however store a quantity energy sufficient to heat up and melt 12 tons of copper!!! 

I suppose that if you were rash enough to put your hand in the LHC beam you'd pretty soon take it out again.

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