Antimatter production source?

[aceshigh]

Where's the evidence that it's easy to hold them even after they've been cooled?  If they were able to hold some as long as 1000 seconds, isn't that because they did manage to cool them, but the fact that they didn't manage to hold them longer than 1000 seconds suggests that even after that much cooling they weren't easy to hold?

the evidence is below. After they were able to hold the atoms for ONE second, they were on ground state. Which is all they wanted. Their objetive was not to hold the anti-atoms for 10 days to prove they could be used on interstellar travel. Their objective was to trap them enough time so they could be studied (they can only be studied when they fall to ground state).

now the important piece of info: why 1000 seconds and not more? Simple because they donīt know if they have anti-atoms there UNTIL they TURN OFF the magnetic confinement!

so what they really did was that after 1000 seconds, they turned off the magnetic field and the atoms smashed against the walls releasing energy, and therefore the scientists knew they were still there until that moment, and the amount.

they could have held them for 10 thousand seconds, or more.

it seems that AFTER they are able to cool the atoms long enough to be properly trapped, the entrapment for longer times gets MUCH easier (only 1 second and already in ground state)


http://www.sciencedaily.com/releases/2011/06/110605132421.htm

"So far, the only way we know whether we've caught an anti-atom is to turn off the magnet," says Fajans. "When the anti-atom hits the wall of the trap it annihilates, which tells us that we got one. In the beginning we were turning off our trap as soon as possible after each attempt to make anti-atoms, so as not to miss any."
Says Wurtele, "At first we needed to demonstrate that we could trap antihydrogen. Once we proved that, we started optimizing the system and made rapid progress, a real qualitative change."
Initially ALPHA caught only about one anti-atom in every 10 tries, but Fajans notes that at its best the ALPHA apparatus trapped one anti-atom with nearly every attempt.
Although the physical set-ups are different, ALPHA's ability to hold anti-atoms in a magnetic trap for 1,000 seconds, and presumably longer, compares well to the length of time ordinary atoms can be magnetically confined.
"A thousand seconds is more than enough time to perform measurements on a confined anti-atom," says Fajans. "For instance, it's enough time for the anti-atoms to interact with laser beams or microwaves." He jokes that, at CERN, "it's even enough time to go for coffee."



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from that last part in bold, what we know is that they never tried to hold the anti-matter atoms for more than 1000 seconds. That was enough for their purpose (make scientific measurements) and therefore they turned off the magnetic field, counted the anti-atoms that had been held, and were content with that.


question: how long can we confine magnetically normal matter atoms? They say in the article the hability to hold anti-atoms is basically the same.

now, fusion reactors struggle to hold atoms of the plasma without leaking EXACTLY because those are VERY ENERGETIC (which is of course a requirement for them to smash together and fuse). Energetic anti-atoms are just as difficult to hold.

but once you cool them down, for how long can you hold them? Forever? What about normal atoms, COOL atoms?

I wouldnīt worry about normal atoms leaking inside the magnetic confinement... obviously, it would be a vacuum.

[frobnicat]

It's not at all my field but I feel like playing with public domain numbers :
10mg of positrons is 1.1E25 (please check)
If stored as non neutral plasma (no antiprotons involved) the Brillouin density limit (due to space charge) at 1T field is on the order of 5E12/cm3. This can be improved quadratically over the magnetic magnitude but the practical densities I see (somehow dated references...) are  more like 1E11/cm3 so I'll assume 5E12/cm3 is optimistic (again, for pure positron cold gas in a trap). That gives 2.2E12 cm3 =  2.2E6 m3 = approx 10 Zeppelin Hindenburg of net storage volume. At 1 Tesla. What would be the mass of the coils and electrodes and generators of such a vessel ?

I miss a short and accessible reference to know the possible energy density of non-neutral (pure positron or pure antiproton) antimatter when taking the storage apparatus mass into account (and with long enough life time that is), anyone knows ?
I'm not saying nano-grams of non neutral antimatter couldn't be useful as "vitamins" to fission or fusion but I don't see how it could be the main fuel to a ship. And neutral cold "trappable" anti-hydrogen seems to be quite hard to produce at significant amounts with decent yields, right now.
http://www.icarusinterstellar.org/antimatter-propulsion-storage-antiparticles/
http://nextbigfuture.com/2011/02/multi-cell-array-of-traps-for.html
More dated http://www.niac.usra.edu/files/studies/final_report/24Howe.pdf

[aero]

So 10 mg needing 10 Hindenburgs volume, is one Hindenburg volume per mg, and 1 mg mass is equivalent to 25 MWhr, or 21.4 ton of explosive. If your numbers are even close to correct then storing antimatter that way is not useful.

Consider that the Space Shuttle main engines generated about 60 GW of power. Of course they didn't burn for an hour but 60 GW continuous power is 1 GW-hr. per minute.

Need a more energy dense storage method for antimatter.

This is not my area of expertise either, so confirm my numbers before taking them to the bank.

[cordwainer]

Big difference in creating enough energy to produce anti-hydrogen versus an anti-particle like an anti-proton or positron. They create positron beams to kill cancers these days, I'm somewhat skeptical that the energy costs would necessarily outweigh the benefits in T/W when it came to a vehicle with an onboard nuclear reactor or large enough solar panel arrays. MSNWR and Gas-Dynamic fusion rocket motors are essentially giant linear accelerators with a plasma injector. Okay, MSNWR uses a liner so it's more like a rail gun with a z-machine at the end but you get the idea. The method mentioned using photon accelerators not only produces larger positron yields but does so with less energy than CERN's atom colliders. I'm just saying somebody should crunch the numbers if you can get better Isp and T/W than even something like HiPEP it might be worthwhile.

[aero]

Big difference in creating enough energy to produce anti-hydrogen versus an anti-particle like an anti-proton or positron. They create positron beams to kill cancers these days, I'm somewhat skeptical that the energy costs would necessarily outweigh the benefits in T/W when it came to a vehicle with an onboard nuclear reactor or large enough solar panel arrays. MSNWR and Gas-Dynamic fusion rocket motors are essentially giant linear accelerators with a plasma injector. Okay, MSNWR uses a liner so it's more like a rail gun with a z-machine at the end but you get the idea. The method mentioned using photon accelerators not only produces larger positron yields but does so with less energy than CERN's atom colliders. I'm just saying somebody should crunch the numbers if you can get better Isp and T/W than even something like HiPEP it might be worthwhile.

The numbers have already been crunched in large part. See

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

In order to go further you need at least a conceptual design of your rocket engine to calculate weight. Thrust then depends on that engine configuration. If you not adding reaction mass (hydrogen, most commonly considered) then your thrust will be quite small even though Isp will be huge. That's because reaction mass will only be the matter+antimatter consumed. If you are adding reaction mass then Isp will go down by the ratio of (matter+antimatter)/ (added reaction mass) but thrust will go up because of that added reaction mass. (Assuming constant energy)