Slashdot Mirror
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?"
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.
If you call hundreds of billions ridiculously minute, then maybe.
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.
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.
How we know is more important than what we know.
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.
No kidding!!! What do you say at this point?
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. 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.)
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.
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.