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Author Topic: How do they separate off certain numbers of atoms?  (Read 1312 times)

Offline Madidus_Scientia

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I was attempting to explain to a friend what Higgs Bosons are and what the Large Hadron Collider does to a friend, who seemed completely satisfied with my explanations apart from one thing - he wants to know how they get an atom or a group of atoms by themselves to inject into the collider. Do they know exactly how many atoms they have?

Am I correct in thinking they must be ions otherwise the magnets couldn't accelerate them? If so do they repel/attract each other in transit?


 

Offline imatfaal

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Re: How do they separate off certain numbers of atoms?
« Reply #1 on: 24/07/2012 13:34:33 »
1. put in a very pure lead sample
2. heat it - I presume not with a bunsen - melt small portion, boil smaller portion, gas of lead atoms
3. high electric current strips a few electrons off a few atoms to make lead ions
4. these ions are accelerated in a linear accelerator - this process strips off a few more electron
5. at a certain energy they go into a dedicated circular accelerator - even faster, higher energy, few electrons
6. join the main feeder route onto the LHC the proton synchrotron  - faster, higher, fewer
7. last stage join the super proton synchrotron - after that very energetic lead nuclei are spat out, electrons all stripped away
8. allowed to play with the big boys on the main LHC
9. accelerated up to full speed

Each bunch of lead ions only numbers a couple of billion ions.  And I guess they do repel each other - but the forces on them mean they still whiz around geneve very quickly whilst repelling each other   
 

Offline evan_au

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Re: How do they separate off certain numbers of atoms?
« Reply #2 on: 24/07/2012 22:01:51 »
They measure the current in the ion beam in milliAmps to Amps. You know how many times a bunch of protons passes a given point in one second, so you can work out how many protons there are from the charge on an electron.

The exact number of protons is not important; even though there are billions of protons in the bunches that collide head-on, only a few of the protons happen to actually hit each other and do "interesting" things in a given revolution around the ring.

All these protons in each bunch do repel each other, so complex magnetic fields are needed to keep squeezing them back into a compact bunch, and electric fields squeeze them so they don't spread out too much along the length of the accelerator. This must be done simultaneously with bending them around in a circular path, and injecting more energy to compensate for the energy lost to electromagnetic radiation as they are accelerated around this circular path.

After the LHC was first turned on, one of the first tasks was to adjust all of these fields so that the bunches of protons could make their way right around the ring without dissipating.

The protons are initially created by an electric arc in hydrogen gas.
 

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Re: How do they separate off certain numbers of atoms?
« Reply #2 on: 24/07/2012 22:01:51 »

 

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