Why dont they say stream of particles

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Discussion Overview

The discussion revolves around the terminology and physical characteristics of particle beams in the context of the Large Hadron Collider (LHC). Participants explore questions related to the nature of particle streams, their behavior, and the implications of interacting with them, touching on both conceptual and technical aspects.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant questions why the term "beam of particles" is used instead of "stream of particles," associating beams more with light.
  • Another participant explains that particles in the LHC move in an ultra-high vacuum and do not touch the walls, suggesting that sounds heard would come from machinery rather than the beam itself.
  • Concerns are raised about the temperature of the underground tunnels, with a participant stating that insulation is crucial to prevent cold temperatures in access tunnels.
  • It is proposed that if a hand were to enter the beam path, it would not feel an impact due to the vacuum, but there could be a risk of radiation burn.
  • A participant provides calculations regarding the cumulative energy of protons in the beams, emphasizing the potential destructive power if a hand were to be placed in the beam.
  • Another participant acknowledges a correction regarding the energy calculations, noting that the energy involved could vaporize a person.
  • Discussion includes a metaphor comparing the energy of the beam to the power of a modern battleship's guns, highlighting the dangers of interacting with the beam.
  • Questions are raised about the relativistic mass of the beams, with calculations provided by participants regarding their rest and relativistic masses.

Areas of Agreement / Disagreement

Participants express varying views on the terminology and implications of particle beams, with some agreeing on the dangers of interacting with the beams while others provide differing calculations and interpretations of energy and mass. The discussion remains unresolved on certain technical aspects and terminology preferences.

Contextual Notes

Participants express uncertainty about the terminology used in physics, the effects of particle beams, and the calculations related to energy and mass. There is a reliance on specific definitions and assumptions that may not be universally agreed upon.

ted hh
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why don't they say "stream of particles"

prepare yourself for an incredibly stupid question. i don't even know if I am posting this right. if I am 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. I am interested and I am 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 don't 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)

thanks

[Moderator edit: email address removed. Do not use the forum to solicit replies by email.]
 
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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
 


Cumulative energy of protons in two beams is around 700 megajoules (200 kwh). (two beams, 2800 bunches/beam, 10^{11} 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.
 


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."

http://en.wikipedia.org/wiki/LHC

- Warren
 


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

I think it was 8000 if I remember correctly, yummy
 


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).
 


What's the relativistic mass of the beam? About 10^-10 grams?
 


Phrak said:
What's the relativistic mass of the beam? About 10^-10 grams?

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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