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Lhc particles harmful to humans?

  1. Jun 25, 2010 #1

    i like a practical approach to everything (as you can see very clearly in this thread, https://www.physicsforums.com/showthread.php?t=411875) so i will ask this question:

    when the lhc is running and colliding particles, if you stood in it, would you see the reaction occuring?, if so what does it look like?

    is it possible to stand in the lhc? is it harmful to do so?, if it is harmful, why is it harmful?

    thanks for your time
  2. jcsd
  3. Jun 25, 2010 #2
    Hi, I might not be the best too answer the questions since my interest is far more theoretical but since no one has I will give it a shot.

    Interesting question. Most of the particles created will not be visible to the human eye. But I since photons are created, and I seen no reason to why all of them should be at higher energies than visible light I expect that you might be able to see a colision as a white spark. However, I dont know if there will be enough of these photons..

    It would be possible to stand in the tunnel where the lhc is built and that should not be very harmful even when they are running at full energy and luminosity. To stand in the actual beam would be harmful, as the protons in the beam would crash into your body, sometimes interacting with the protons inside you and thus damage the tissue. If you were to stand next to a collision that would probably be dangerous as well, at least if you stayed there for a long time (many collisions).

    Perhaps somebody else can make things more quantitative.

  4. Jun 25, 2010 #3


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    It is a nice exercies to calculate the energy stored in the beam. All what you need is special relativity and some facts about the LHC beam parameters.

    I found this page - unfortunately in German: http://www.lhc-facts.ch/index.php?page=strahlenergie

    They are saying that the stored energy is 350 MJ which corresponds to the kinetic energy of a car with approx. 1000 mph.
  5. Jun 25, 2010 #4
    But most of that energy will just pass right through the human body without interacting, unlike a car. I was told once that standing in the beam when a bunch passes through would feel like a punch in the stomach, but I dont know how accurate that description is.
  6. Jun 25, 2010 #5


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  7. Jun 25, 2010 #6
    That is not true.

    The reason for this is that the beam particles will pass through your body without interacting. The impact it has on your body does not depen on the energy of the proton beam, but on the energy that beam deposited in your body.

    As an analouge you can take the constant flow of neutrinos that pass through our body in huge numbers every second. But only one or two of them will interact with you during your entire lifetime. Therefore the energy flowing through you does not have any impact.
  8. Jun 25, 2010 #7


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    That depends on the luminosity. One could get a rough estimate based on the total scattering cross section of a proton with H and O in water. But if you look at the damage, I would say that it's rather dangerous (of course the photopraph shows metal, that makes a difference)
  9. Jun 25, 2010 #8


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    Neutrinos only interact through the weak interaction, so they have a very small probability of interacting with the atoms in your body. Protons (which is what the LHC beam is made of ) are charged particles and interact strongly with matter. They will quickly deposit a lot of energy in a short distance. Below is a link with some of this information. A 1 GeV proton has a range of about 2cm in your body. The TeV protons in the LHC might make it through your body, but in passing through they will deposit more than enough energy to kill you.

    http://www.nucleonica.net/wiki/index.php/Help:Range_%26_Stopping_Power [Broken]

    http://www.nucleonica.net/wiki/index.php/Help:Range_%26_Stopping_Power [Broken]
    Last edited by a moderator: May 4, 2017
  10. Jun 25, 2010 #9


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    Even if we accept your statement that one bunch is like a punch in the stomach as correct, each beam contains 2808 bunches. How about 6000 punches in the stomach in a fraction of a second?
  11. Jun 25, 2010 #10

    thanks for your reply! :)
    hmmm it doesnt look like someone else will make it more quantitative than you haha,
    i have a strange idea that the collisions would produce a purple-blue glow, but i think ive got that idea from seeing this picture:
    http://brian-mcdermott.com/20kv.JPG [Broken]

    do you think standing in the beam would cause permanent damage?, could it be fatal?, how long would it take to cause permanent damage, and how long would it take to kill the person standing in the beam?

    did you that you could achieve nuclear fusion easily for a few thousand dollars?
    well you can! : http://brian-mcdermott.com/

    thanks again for your help
    Last edited by a moderator: May 4, 2017
  12. Jun 25, 2010 #11


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    Last edited: Jun 25, 2010
  13. Jun 25, 2010 #12
    I would like to know where you get the 2cm for a 1GeV proton from? Can you give me a reference?
    From what I understand, the range should increase with increase energy, and "The range of a 125 MeV proton in tissue is 12 cm., while that of a 200 MeV proton is 27 cm."
    According to http://www.physics.harvard.edu/~wilson/cyclotron/Bob_Wilson_Radiology.html

    Also the energy deposit decreases with increasing energy, which means that a TeV proton will deposit very little of its energy.

    The remark about the large number of bunches is true, and if the punch in the stomach analogue really works, well.. it does not take much imagination to know what would happen then.

    Perhaps someone with more info know something like the mean free path of a proton in water, at TeV energies.
  14. Jun 25, 2010 #13


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    When the beam is running collisions with any remaining air molecules in the beam line and beam wandering that causes protons to hit the walls also generates radiation.

    So the tunnel is a no-go area when powered up and for a short while after.
  15. Jun 25, 2010 #14


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    I think you're right that it is not as bad as I said, but it still looks like enough to kill you. I made an exponent mistake before - the range of a 1GeV proton in water is about 200cm (158cm, according to the reference below), not 2 cm as I said before. Let's try and do it more carefully. I found an excellent reference from NIST on range and stopping power of protons:


    This only goes up to 10 GeV, but notice that at 10 GeV we are out of the regime where dE/dx ~ 1/E. I think this is because of the Fermi correction to the Bethe formula, where the protons have become relativistic enough that they are seeing a higher density of matter due to relativistic length contraction. So let's calculate how much energy the beam would deposit at 10GeV. This is as high as the NIST tables go, and you can see that the energy deposition rate is starting to increase at the end of the graph, so this appears to be a conservative assumption. At 10 GeV, dE/dx = 4.5 MeV-cm^2/g, which, since the density of water is 1.0 g/cm^3, gives 4.5 MeV/cm. Assuming your body is about 20 cm thick, this means each proton deposits about 90 MeV of energy. The LHC has ~ 3E14 protons in the beam, so the total energy deposited is ~ 9E7eV x 3E14 x 1.6E-19 ~ 3000J. So, not like getting hit with a car, or even a 10,000J rifle bullet, but I still think it would kill you. Looking at the picture of the metal plate that tom.stoer uploaded, I'm sure not going to stand in the beam!!
  16. Jun 25, 2010 #15


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    Isn't the LHC beam in a vacuum?
  17. Jun 25, 2010 #16

    Andy Resnick

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    You wouldn't see anything, but in the collider chamber (if you could fit yourself inside), you would be subject to a lot a radiation and would likely die.

    In the beamline itself, you would be subject to radiation damage as well. Google "proton therapy" to see how the mechanism works. It's not like getting punched, at all. The deposited energy depends on the energy of the proton.
  18. Jun 28, 2010 #17

    thanks for your help, i appreciate it xx :)
  19. Jun 28, 2010 #18
    thanks for all of your replys, you were very helpful, i really appreciate it :) xx
  20. Jun 28, 2010 #19
    The beam indeed does circulate in a vacuum. This means you would need some sort of breathing apparatus. Also, the entire beamline is cooled to something like 70 K (~-200 C), so you would rapidly freeze to death if you were in contact with anything.

    Additionally, your body heat might result in nearby superconducting magnets quenching, which I've heard is a very violent process, though I'm not sure how.
  21. Jul 10, 2010 #20
    thanks for all of your help, i greatly appreciate it :)
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