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Design Starting For Matter-Antimatter Collider 191

Posted by samzenpus
from the dump-the-warp-core dept.
couch_warrior writes "The Register is carrying a story on the early design efforts for the next generation of high-energy particle accelerators. They will be linear, and will collide matter and antimatter in the form of electrons and positrons. The obvious question will be: once we have a matter-antimatter reactor, how long till we have warp drive, and will the Vulcans show up for a sneak-peak?"
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Design Starting For Matter-Antimatter Collider

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  • Re:Wrong Question (Score:5, Informative)

    by 1s44c (552956) on Thursday October 08, 2009 @03:17AM (#29678021)

    Actually, I think the next question would be: "Now how can get some antimatter?"

    It's my understanding that we can only manufacture ridiculously minute quantities of the stuff, and that may take more energy to make than we'll get out of it anyways.

    It WILL take more energy than we can get out of it. They have to make the positrons first before destroying them.

    The point of this is to see how the particles behave to validate or disprove current theories. This isn't being done to make an unlimited source of energy.

  • Re:Wrong Question (Score:4, Informative)

    by Archaemic (1546639) on Thursday October 08, 2009 @03:17AM (#29678027)

    If you call hundreds of billions [cosmosmagazine.com] ridiculously minute, then maybe.

  • Duh! (Score:5, Informative)

    by andre.david (1373517) on Thursday October 08, 2009 @03:18AM (#29678029)

    There's a matter-antimatter collider in production since the 1990's. It's called the Tevatron, it collides protons with antiprotons and it is in Illinois.

  • Re:Wrong Question (Score:5, Informative)

    by QuantumG (50515) * <qg@biodome.org> on Thursday October 08, 2009 @03:45AM (#29678155) Homepage Journal

    Oh yeah, I love that news wire article.. it was repeated dozens of times in different magazines and news papers. Unfortunately, no-one has bothered to actually track down a reference to a scholarly publication for it. In fact, there is none, the technique was presented at a conference and no-one has reproduced it.. there's no papers quantifying exactly how much antimatter was made and at what temperatures.

  • Re:Duh! (Score:5, Informative)

    by Gromius (677157) on Thursday October 08, 2009 @04:01AM (#29678215)
    And just to add to this. All particle colliders are mater-antimatter colliders, it just doesnt work otherwise (charge conservation) Thats right, every single particle collider where you are annihilating the particle is matter-antimatter.

    Now before somebody says, but the LHC is proton-proton, you suck, the LHC is actually a quark-anti quark or gluon-gluon collider. Protons are not just 3 quarks, due to the strong interaction there is also a sea of gluons and quark-anti quark pairs which carry the momentum of the proton. At the energies of the LHC, this sea becomes important.

    The article is terrible and horribly confused. Reads like something from the Sun (a gutter British newspaper for non Brits).
  • Re:Wrong Question (Score:4, Informative)

    by Sockatume (732728) on Thursday October 08, 2009 @04:14AM (#29678291)

    Hundreds of billions still ain't a lot when you're talking about nucleons for use as a fuel. When you annihilate it you should get about ten joules, or enough to raise the temperature of a tiny drop of water by a couple of degrees.

  • by jfb2252 (1172123) on Thursday October 08, 2009 @09:06AM (#29679985)

    As preparation for the PET scan you were given an injection with a radioactive tracer which decays via positron emission. The PET scanner doesn't generate any radiation, it simply detects the 511 keV gamma rays produced when the positrons in the tracer annihilate with an electron.

  • Re:Wrong Question (Score:5, Informative)

    by JustinOpinion (1246824) on Thursday October 08, 2009 @09:10AM (#29680009)
    In a PET scan, the positrons are produced as a by-product of a nuclear decay. Basically a radioactive isotope is injected into the person, and this isotope decays over time, emitting positrons. The isotopes are usually generated on-site using a cyclotron [wikipedia.org]. The number of positrons emitted during a PET scan is not so large (each blip on the detector is a single decay event), and a cyclotron is relatively expensive. Producing positrons in this way might be cheaper (per particle) than producing them in an accelerator. (Similar techniques are used as a scientific probe, e.g. positron annihilation spectroscopy [wikipedia.org].)

    But quotes for the "free market cost of antimatter" are based on the fantastic costs of generating it in an accelerator. The reason being that radioactive decay is suitable for producing positrons that emit from a substance (in every direction), but is not a viable way of capturing said positrons and using them for anything else. An accelerator, instead, can generate anti-particles and capture them (e.g. using magnetic fields) and "keep" them somewhere (e.g. in a storage ring). Also worth noting is that accelerators can create not just positrons (anti-electrons) but also anti-protons, and even "true antimatter" such as anti-hydrogen (positrons + anti-protons), albeit for a very, very short time.

    So depending what kind of antimatter you want, where you need it, and whether or not you need is stored, the price can vary. But all known methods for producing any sort of antimatter require significant input of effort and energy, and are correspondingly expensive.
  • Re:antimatter (Score:5, Informative)

    by Dragonslicer (991472) on Thursday October 08, 2009 @09:12AM (#29680025)

    I thought it had something to do with time... Like, positrons were electrons going the other way in time, which is why they annihilate when they collide and produce a photon. Really the electron is hitting a photon and turning around in time. Likewise with pair production. Anyone know if this is right? I honestly think that quantum physics book was chock full of lies...

    If I remember correctly, that theory comes from Feynman diagrams. It is a pretty interesting theory, and you can get some other very interesting ideas out of it. As with most other aspects of particle physics, how "true" it is can be debated at length, but the mathematics works, which is probably enough for most physicists.

  • Re:antimatter (Score:1, Informative)

    by ShadowXOmega (808299) on Thursday October 08, 2009 @09:34AM (#29680269)
    Anti-Matter is like matter, but with a opposite
    property (spin, charge, etc) that nullify between
    them, releasing photons (and neutrinos and
    another fancy particles)

    Actually, you can collide anything vs anything,
    but you need to see the quark composition of the
    particles to try to predict the outcome (pretty
    hard, cause everything will collide vs
    everything, primarly the target ones, next the
    newly formed particles, just with fewer
    interactions...

    from wikipedia http://en.wikipedia.org/wiki/Antimatter [wikipedia.org]

    "In particle physics, antimatter is the extension of the concept of the antiparticle to matter, where antimatter is composed of antiparticles in the same way that normal matter is composed of particles. For example, an antielectron (a positron, an electron with a positive charge) and an antiproton (a proton with a negative charge) could form an antihydrogen atom in the same way that an electron and a proton form a normal matter hydrogen atom. Furthermore, mixing matter and antimatter would lead to the annihilation of both in the same way that mixing antiparticles and particles does, thus giving rise to high-energy photons (gamma rays) or other particleâ"antiparticle pairs."
  • by smolloy (1250188) on Thursday October 08, 2009 @09:35AM (#29680275)

    FYI -- I work on this project, and I work with Roger Jones (the guy in the article), so I know a substantial amount about this.

    Your definition of damping is quite right, but your definition of detuning is, in this case, not really what he means. What he means is taking a cavity, and changing its shape in order to "detune" some cells.

    To explain:

    The cavities are traditionally built in such a way that each cell rings (like a bell) at the design frequency of the accelerating rf. Since all of the cells are identical, the beam will excite exactly the same mode frequencies in each one (like a hammer hitting a bell). Since they are resonant with each other, they can and will ring coherently. Thus the amplitude of these modes will be proportional to N^2 (where N is the number of cells).

    If they are made to have slight differences (detuned) that cause their resonant frequencies to be slightly different (but still within the bandwidth of each other due to their finite Q -- so they *can* excite one another), they will ring incoherently. This causes the mode amplitude to be proportional to N.

    Thus, the amplitude of the incoherent ringing will be lower by a factor of N.

    On top of this, they also add absorbing material to take out some of the power (the damping you refer to), and it is this that fits your guitar string analogy, not the detuning that Roger was referring to in the article. Absorbing material cannot change the frequency of the oscillation -- all it can do is remove energy from it, thus damping it's amplitude.

    To go further, yes the differing stiffnesses of the springs under my car *does* look like a system of bells ringing at different frequencies. They are each ringing at a different "pitch" in order to detune any destructive vibrations. Your car analogy, including the absorbing rubber, is almost perfect! :)

    I think the confusion is coming from the fact that this system can use both the absorbing material that fits your guitar string analogy, and the detuning technique that fit's Roger's bells. His analogy *does* describe the system very well, and I hope you can see that now.

  • by Anonymous Coward on Thursday October 08, 2009 @10:45AM (#29681125)

    Actually, the technical paper was published a few months later, in one of the most respected scientific journals in the world, Physical Review Letters. Please see "Relativistic Positron Creation Using Ultraintense Short Pulse Lasers" H. Chen, et. al., Phys. Rev. Lett. 102 , 105001(issue of 13 March 2009) In addition to this, these results were also reproduced at the LLE laser facility at the University of Rochester, where an order of magnitude more positrons were observed, over what was reported in the original new release.

  • Re:antimatter (Score:2, Informative)

    by Anonymous Coward on Thursday October 08, 2009 @11:01AM (#29681319)

    Here's the basic concept: positive-energy antiparticle travelling forwards in time == negative-energy particle travelling backwards in time. Note that in the 'real' world, only positive energies are possible, so we observe both particles and antiparticles with positive energy.

    In a bit more detail:

    The expression for the propagation of the particle contains an oscillating exponential term:

    exp(-i*E*t)

    where E = energy and t = time (hbar is set to 1).

    Using the equivalence I mentioned above, both energy and time are multiplied by -1 for an antiparticle, so we have:

    exp(-i*-E*-t) == exp(-i*E*t)

    - so the net result is the same in reality.

    Feynman diagrams don't show time flow - just 'beginning', 'middle' and 'end'. However all antiparticles are drawn with 'backwards' arrows to reflect the situation described above. Even though in reality they are travelling forwards in time, we can also think of, say, an electron colliding with a photon and then moving away backwards in time, as alluded to in the GP. It's a piece of mathematical trickery or a fundamental underlying truth, take your pick...

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