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Why dont they say stream of particles

  1. Sep 10, 2008 #1
    why dont they say "stream of particles"

    prepare yourself for an incredibly stupid question. i dont even know if im posting this right. if im intruding on a discussion please excuse me. i just now registered because this question was bugging me. i doubt ill stop back to this forum so if someone could send me an answer to my email id appreciate it

    actually it is several questions that bother me when i read the articles about the hadron machine. im interested and im sort of trying to picture the situation. it all seems pretty surrealistic to us laypeople:

    1. if you are standing next to the hadron tube i see in the photos would it make some noise while they were sending the particles through it?

    2. if it makes a noise what is the noise like?

    3. are the underground tunnels incredibly cold when the thing is in use?

    4. when they say "beam of particles" why dont they say "stream of particles". i always think of beams as having to do with light

    5. if you stuck your hand in the beam or stream of particles would you feel an impact?

    6. what would it do to your hand?

    i realize these are naive and stupid questions but i found the experiment interesting and want it to be a little more real for me

    please remember to send replies to my email (if anyone replies)


    [Moderator edit: email address removed. Do not use the forum to solicit replies by email.]
    Last edited by a moderator: Sep 10, 2008
  2. jcsd
  3. Sep 10, 2008 #2


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    Re: Where do the particles come from in collisions?

    1) The particles are moving in an ultra-high vacuum, and never (intentionally) touch the walls of the pipe. You'll definitely hear sounds from all the machinery, magnets, circulating coolants, etc. -- but you won't hear any sounds from the beam itself.

    2) N/A

    3) No. Great pains are taken to insulate parts of the apparatus that operate at very cold temperatures. If the access tunnels became very cold, it would be an indication of poor insulation (and thus very wasteful designs).

    4) The term 'beam' is used everywhere in physics to describe either particles or photons. You'll just have to get used to it.

    5) You wouldn't be able to, because the particles move in an ultra-high vacuum, and that would preclude your hand being stuck in the beam path. If you were somehow able to do this, you would not feel an impact, as in catching a baseball, though you might get a radiation burn. Even though the particles are accelerated to fantastic speeds, there aren't that many of them. They don't contain a very large amount of energy, even all together.

    6) N/A. Radiation burn, maybe, if anything at all. And it would take quite a while.

    - Warren
  4. Sep 10, 2008 #3
    Re: Particles

    Cumulative energy of protons in two beams is around 700 megajoules (200 kwh). (two beams, 2800 bunches/beam, [tex]10^{11}[/tex] protons/bunch, Lorentz factor 7500, do the math) To give you an idea how much it is - you can bring two TONS of water from room temperature to the boiling point with that much energy.

    Beams themselves are very thin, but your hand would scatter protons and they would start hitting everything around you.

    Basically, if you somehow get inside the pipe and stick your hand into the beam while it's operating at full capacity, you will end up vaporizing your hand, yourself, and a good chunk of pipe.
  5. Sep 10, 2008 #4


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    Re: Particles

    Thanks for the post, hamster143, I stand corrected. I didn't realize they were using 10^11 protons per bunch! I should have looked up the figures before making my statements. You're right, 175 kWh of energy would easily vaporize a person. From Wikipedia: "the beam dump must absorb an energy equivalent to that of a typical air-dropped bomb."


    - Warren
  6. Sep 10, 2008 #5


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    Re: Particles

    A teacher at my depertment illustrated yesterday on the LHC-party we had to the undergrads how many choclate bars that where travelling in LHC ;-)

    I think it was 8000 if I remember correctly, yummy
  7. Sep 10, 2008 #6


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    Re: Particles

    Yea in essence, about 1 second of a beam is roughly equivalent to the power a modern battleship deposits when it fires its primary guns. So not recommended to stick your hand in there.

    It can be potentially really dangerous too. If the beam vears off track by just a fraction of a milimetter, it can cause great mechanical stress on the magnets, not to mention what would happen if it actually hit a wall or sensitive electronics (you'd have a fried detector and a nasty radiation leak).
  8. Sep 10, 2008 #7
    Re: Particles

    What's the relativistic mass of the beam? About 10^-10 grams?
  9. Sep 11, 2008 #8
    Re: Particles

    Rest mass of two beams taken together is 10^-9 grams, relativistic mass would be 7.5*10^-6 grams.

    That's at full power and luminosity, of course.
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