The blog of Xeno, a slightly mad scientist
Antimatter, created naturally above storm clouds, has now been created by device that uses magnets and tabletop lasers fired at a gold sheet through helium gas.
A team of physicists working at the University of Michigan just published a paper about their device in Physical Review Letters. But basically, it’s small enough to sit on a table and can create positrons – anti-electrons – like its big,big brother, the particle accelerator at CERN. Positrons, if you aren’t familiar, are found around black holes and pulsars.
PhysOrg explains the process in more detail:
The team fired a petawatt laser at a sample of inert helium gas. Doing so caused the creation of a stream of electrons moving at very high speed. Those electrons were directed at a very thin sheet of metal foil which caused them to smash into individual metal atoms. Those collisions resulted in a stream of electron and positron emissions – the two were then separated using magnets.
The researchers report that each blast of their gun lasts just 30 femtoseconds, but each firing results in the production of quadrillions of positrons – a density level comparable to those produced at CERN.
For scale: petawatt is one quadrillion watts, a femtosecond is a one quadrillionth of a second, and a quadrillion is 1,000,000,000,000,000.
The thought is that we can use gadgets like this to study positrons more easily than ever and learn more about those gaping black holes in space and other things like them. … [PhysOrg]
From the Wikipedia antimatter bomb page:
An antimatter weapon is a hypothetical device using antimatter as a power source, a propellant, or an explosive for a weapon. Antimatter weapons do not currently exist due to the cost of production and the limited technology available to produce and contain antimatter in sufficient quantities for it to be a useful weapon. The United States Air Force, however, has been interested in military uses — including destructive applications — of antimatter since the Cold War, when it began funding antimatter-related physics research. The primary theoretical advantage of such a weapon is that antimatter and matter collisions convert a greater fraction of the weapon’s mass into explosive energy when compared to a fusion reaction, which is only on the order of 0.7%. There is considerable skepticism within the physics community about the viability of antimatter weapons. According to CERN laboratories, which regularly produces antimatter, “There is no possibility to make antimatter bombs for the same reason you cannot use it to store energy: we can’t accumulate enough of it at high enough density. (…) If we could assemble all the antimatter we’ve ever made at CERN and annihilate it with matter, we would have enough energy to light a single electric light bulb for a few minutes.”, but this would be a considerable feat because the accumulated antimatter would weigh less than one billionth of a gram.
If those scientists at the University of Michigan made just 12 grams of antimatter they’d have enough energy to light all 12 billion lightbulbs in the world for a few minutes.
Universe Today has this to say:
Antimatter is powerful. Even a tiny amount would create a devastating explosion. Just a kilogram of antimatter would release the same amount of energy as a 20 megaton thermonuclear bomb.
But here’s the problem. Generating antimatter is an incredibly expensive process. It’s been estimated that if you took all of the antimatter ever created in all the particle colliders in the world, you would only have enough to power a lightbulb for a few minutes. To create antimatter on an industrial scale to create an antimatter bomb would require the collective resources of the entire planet. Furthermore, there’s no easy way to store antimatter once you create it, since it will explode with even the slightest touch with regular matter.
There’s no risk of an antimatter bomb ever being created. Perhaps in the distant future, hundreds of years from now, but not any time soon. …
1 kilogram is 1,000 grams so we can estimate roughly that 1 gram of antimatter has the power of a 20 kiloton nuclear bomb. That’s more powerful than the bomb dropped on Hiroshima (13 to 18 kilotons).
Scaled up and put to good use this invention might solve world energy problems… unless it takes more energy to generate, separate and store the antimatter than could be recovered using it as a fuel.
Storage is tricky:
“Trapping antihydrogen proved to be much more difficult than creating antihydrogen,” says ALPHA team member Joel Fajans, a scientist in Berkeley Lab’s Accelerator and Fusion Research Division (AFRD) and a professor of physics at UC Berkeley. “ALPHA routinely makes thousands of antihydrogen atoms in a single second, but most are too ‘hot’”—too energetic—“to be held in the trap. We have to be lucky to catch one.”
The ALPHA collaboration succeeded by using a specially designed magnetic bottle called a Minimum Magnetic Field Trap. The main component is an octupole (eight-magnetic-pole) magnet whose fields keep anti-atoms away from the walls of the trap and thus prevent them from annihilating. Fajans and his colleagues in AFRD and at UC proposed, designed, and tested the octupole magnet, which was fabricated at Brookhaven. ALPHA team member Jonathan Wurtele of AFRD, also a professor of physics at UC Berkeley, led a team of Berkeley Lab staff members and visiting scientists who used computer simulations to verify the advantages of the octupole trap….