Don't Cross the LHC Stream! (Maybe) 171
jamie points out this piece from always-entertaining Bad Astronomer Phil Plait, who asks this week the simple question "What happens if you put your hand in the beam of the Large Hadron Collider?" The thrill of discovery to me doesn't sound worth the worst-case scenario.
Already happened before (Score:5, Informative)
"So it was in 1978 that when the proton beam entered Anatoli Bugorski's skull it measured about 200,000 rads, and when it exited, having collided with the inside of his head, it weighed in at about 300,000 rads. Bugorski, a 36-year-old researcher at the Institute for High Energy Physics in Protvino, was checking a piece of accelerator equipment that had malfunctioned - as had, apparently, the several safety mechanisms. Leaning over the piece of equipment, Bugorski stuck his head in the space through which the beam passes on its way from one part of the accelerator tube to the next and saw a flash brighter than a thousand suns. He felt no pain.
http://www.wired.com/wired/archive/5.12/science.html [wired.com]
It's already happened once. (Score:5, Informative)
Don't cross any high-energy streams, definitely. (Score:4, Informative)
Someone I know had the small child of a neighbor flash him in the eye with a cheap Chinese red laser pointer some time ago, and got a permanent scar on his retina and a second "blind spot" in one of his eyes. Apparently, the pointer was a little bit too powerful in the IR region than it should have been.
Moral of the story - avoid high energy beams regardless of the wavelength or the particle kind because you never know what will slip by even in a supposedly "safe" circumstances.
Re:It's already happened once. (Score:5, Informative)
If you read the link in the comment that you're replying to, you'd see that the guy took "500 times the presumed lethal dose" of particle spunk to the face/brain, and survived with nothing more than all the nerves in the left side of his face dying. Even completed his PhD.
Odd (Score:5, Informative)
I don't know of any red lasers that have IR components. Lasers are, by definition, monochromatic. That's the idea after all. The reason some have IR as well is they are DPSS. They produce IR radiation directly, a frequency doubler then takes it up to the visual range. That's a lossy process, so the IR is much higher than the final output, hence an IR filter is needed. Green lasers work this way, at least all the ones I've seen. However red laser pointers are all direct drive, the diode outputs the frequency you want. That's why they are used for CDs and so on, keeps the cost down.
That is also the big deal with Blu-ray lasers (actually quite violet, not blue). Again, direct diode lasers. Means they cost less, use less space and so on, and of course being violet have a higher wavelength.
I've never heard of a red DPSS laser pointer.
Re:Already happened before (Score:3, Informative)
That quote makes it sound like he died.
Apparently he lived with no major disabilities.
it sounded like he was just very ungly afterwards and had seizors, but retained similar mental capabilities.
Re:Already happened before (Score:3, Informative)
total energy in the beam equals 173 kilograms TNT (Score:4, Informative)
The total energy in the beam is 724 MJ (173 kilograms of TNT) (energy stored in magnets are 10x this) That is a bomb big enough to take out a school.
It would be hard to get your hand into vacuum, but imagine a space suit arm attached to a sandblast cabinet.
The beams energy would hit your hand in a spot d1mm. It would most certainly deposit all its energy there until that part of your hand became a vacuum. Probably similar to a laser knife. In addition, your flesh that obstructed the beam would give off a lot of radiation as it burned away. Imagine Hiroshima 1km away x10^8 on that part of your body.
Every proton would not hit something in your hand on first encounter, but if it missed, it would just loop around, and hit on a later time. The result would be the same. In a short time, your hand and your space glove would have a hole through it. More likely a straight cut from where you put it in. Anything nearby would be exposed to a good dose of radiation as these collisions would be quite "dirty".
Re:From the comments below the article... (Score:5, Informative)
12. Bethany Says:
September 21st, 2010 at 8:20 am
Alright, here's what I calculated:
The protons are high energy with lorentz factor of gamma=7500, kinetic energy is about K=7×10^6 eV. The paper cited below says that the stopping power of a proton going 10^6 eV is about 2.5×10^8 eV cm^2 g^-1. Using the density of muscular tissue rho=1g cm^3 and the thickness of my hand of 1 cm, the energy deposited is 2.5×10^8 eV. In other units its 1.07×10^-11 calories, 4.49×10^-11 Joules, and 1×10^-14 grams of TNT. If there are hundred billion protons per bunch in the beam (as the video said) then for every bunch you get 4.49 Joules or 0.001 grams of TNT of energy. (emphasis mine)
There are two beams, each of which contains 2808 bunches. Don't worry about the effect of multiple passes, though, since there won't be any tissue left in the beam's path by the time the first pass is over.
A more informative comment showed up later:
31. Xerxes Says:
September 21st, 2010 at 10:45 am
I think the hand-beam question is best answered by this document: http://lsag.web.cern.ch/lsag/BeamdumpInteraction.pdf [web.cern.ch]
Granted, a carbon block isn't an exact model of the human hand, but it's probably close enough. The key points are:
1) "this energy deposit over 85 s is long enough to change the density of the target material. The density decreases at the inner part of the beam heated region because of the outgoing shock waves in the transverse direction. As an example, after the impact of 200 bunches with a size of = 0.2 mm, a maximum temperature of 7000K and a density decrease by a factor of 4 is expected." The results of heating your hand to 7000K and increasing its volume by a factor of 4 are probably best not imagined. Since a full beam is 2808 bunches instead of 200, you might want to scale that by a factor of 10 too.
2) But on the other hand (hehe): "The beam tunnels through the target and deposits the energy with a penetration depth of 10 m to 15 m" Since your hand is not 10m thick, you won't pick up the full effect. This paper goes into some detail of the spatial distribution of the energy dump: http://cdsweb.cern.ch/record/972357/files/lhc-project-report-930.pdf [cdsweb.cern.ch] So at hand-thickness of 2ish cm, you'd only get maybe an eighth of the effects of #1, so your hand will only reach the more modest temperature of 1000K (times 10 for a full 2808 bunches?). The shockwave from the blast will extend several cm in the transverse direction; translation, the rest of your hand will be blown off by the middle of your hand exploding. Probably the part of the accelerator apparatus downstream of your hand picks up the rest of the energy. The rest of you probably wouldn't want to be standing next to it when it blows.
Cool pictures of the effects of a low-energy (450-GeV) beam on copper plates are in http://dx.doi.org/10.1109/PAC.2005.1590851 [doi.org]
(I spent so much time looking up references, several other people made the same points. Oh well.)
Note particularly the fact that if one beam hit the solid graphite beam dump without being swept around during the pass, the surface would be at 7000 C, and would be well in the process of exploding, by the time the first 200 bunches had hit. Your hand, having a lower boiling point than graphite, would begin to remove itself from the path of the beam somewhat sooner, and would therefore probably absorb rather less energy. That may be small consolation, though, since it pretty much means that the splattered remnants of your hand wouldn't be as intensely radioactive as the carbon in the beam dump would be.
Re:Acrylic... (Score:5, Informative)
Slightly different, as what the artist does is actually charge up the acrylic block with excess electrons (like a supersaturated chemical solution) that have nowhere to go because of the acrylic and surrounding air acting as an insulator. Then he takes a nail to the start of the "lightning", and hammers it in which creates a ground (just like what happens in charged thunderclouds when lightning strikes), creating the effect so reminiscent of lightning.
You can see it in this video:
http://www.youtube.com/watch?v=F-X5QAV0Rtk [youtube.com]
They start with a charged up piece of acrylic, and it's obvious that the effect is not from the beam itself but from the geometry of the piece of acrylic and the grounding path they introduce.
Re:Don't cross any high-energy streams, definitely (Score:4, Informative)
Incorrect. Lasers use a highly focused parallel high energy beam. Because it's high energy, it can burn. By projecting the focused parallel beam through a convex lens (the eye's lens) you refocus the beam and all the parallel high-energy photons focus on a point. This point light then burns the back of the cornea. Like looking directly at the Sun. Or focusing a magnifying glass on a leaf on a sunny day. Has nothing to do with IR and everything to do with optics and energy levels.
Re:It's already happened once. (Score:5, Informative)
Actually, if you read it, his face swelled up so much it was not recognizable, his skin fell off, revealing the path of the beam though his skull and brain, and he now has epilepsy.
He lived and can function because the path of the beam was pure luck. Had the beam passed through a different part of his brain he may have died, or become a vegetable. There was a case of a man in the 1800s, working on a railroad who had a steel rod shoot through his head, and took a large section of his brain with it. He was not expected to live. But he did, but his personality was altered by the loss. He still retained much of his memory and abilities.
Alzheimer's is a slowly progressive disease, which takes away parts of the brain over time, yet many of these people can still function for years.
The fact is there are several factors involved, but it's fairly likely any living tissue subjected to a beam from the LHC is going have many cells destroyed. Think of something like laser surgery, but with a much bigger beam.
Re:Simple (Score:4, Informative)
Well there is the slight problem of actually getting to the beam.
I think MythBusters are going to pass on this one.