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Design Starting For Matter-Antimatter Collider
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?"
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?"
Maybe in a Star Trek convention...
Keptin, I'm giving you all she's got!
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?"
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.
Unfortunately, a matter/anti matter reactor is not enough to create an Alcubierre drive.. We still need some Exotic Matter.. And a lot of it..
So .. go back to sleep.. nothing to see here..
--Ivan
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.
There were already some electron-positron colliders, the LEP for example. I think the new thing about this collider is that it is a linear and for high energy. In an electron/positron synchrotron the particles are flying in circles, permanently loosing energy to synchrotron radiation. This is why a linear design will allow to achieve higher energies.
Peak: top of a mountain.
And the daily Slashdot malapropism award goes to samzenpus.
It's about wakefields and the possibility of reducing their external effects by detuning. What makes this interesting is that the proposals for next-gen small accelerators are about deliberately using wakefields to achieve very high acceleration over very short ranges, effectively getting particles to surf on laser-induced wakefields.
The guy with the proposal also manages to give a spectacularly bad example of detuning - bells, anyone? - which fully complies with the Bad Analogy requirements, i.e. detuning is nothing at all like having lots of bells, and the analogy doesn't provide any insight at all into what is happening. Detuning is more like resting a finger gently on a vibrating guitar string.
All this article really tells me is that wakefields are very hot in particle accelerator research, and efforts are focussing on reducing their unwanted effects as well as extracting more energy from them.
From scarped cliff or quarried stone she cries "A thousand types are gone, I care for nothing, no not one."
maybe by Prostetnic Vogon Jeltz himself now back to the poetry
Kind of like your karma points for that comment ;)
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...
When you're afraid to download music illegally in your own home, then the terrorists have won!
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.
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.
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.
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...
There can be only 1.
Why is it so hard to only have politicians for a few years, then have them go away?
Redundant? No, it was an honest mistake and I really don't think that moderation was fair. It's quite clear he had meant to type "fr1st p0st!!!" but had his hand offset on the home row by one while he was typing. Growing up on Macs which had the little keyboard indicator nubbies under the middle fingers instead of the index fingers, I would frequently type out something in the IRCs and not realize my mistakeuntil I had already told everybody gege tgat;s wgat tiyr nin saud kast buggt!!
+1 Disagree