Gamma-Ray Annihiliation Lasers

Gamma-ray annihilation lasers!

[S]cientists in the US have successfully combined electrons with their anti-matter counterparts, positrons, to create Di-positronium, bringing the dream of gamma-ray annihilation lasers one step closer to being realized.

The discovery, reported in the journal Nature, is a key step in the creation of ultrapowerful lasers known as gamma-ray annihilation lasers.

"The difference in the power available from a gamma-ray laser compared to a normal laser is the same as the difference between a nuclear explosion and a chemical explosion," said Dr David Cassidy of the University of California, Riverside, and one of the authors of the paper.

"It would have an incredibly high power density."

Gamma. Ray. Annihilation. Lasers.

Sounds like lasing a stick of dynamite to me. Well played, Mr. Knight.

I have no idea what I'm talking about, but it seems they've found a way to make positrons take up the orbits of normal electrons in normal matter, creating (if only for a few nanoseconds) a molecule which has both matter and anti-matter electrons whizzing about it. And I guess if they can extend that very short shelf life, they'd have the most potent short-burst energy container in the universe, as a matter-antimatter annihilation results in 100% pure direct conversion of mass to energy. Unlike a petty nuclear reaction, which usually only manages to convert, what?, 10% of the mass involved into energy.

Somehow (follow through the links) this is interesting to those researching fusion. Then again, those people are interested in practically anything, because living lives of scientific futility has to get old after a while.

Dr Cassidy believes that increasing the density of the positronium in the silicon would create an exotic state of matter known as a Bose-Einstein condensate (BEC).

BECs are usually produced by supercooling atoms so that they merge and begin to behave like one giant atom.

They have been used in many experiments such as the 2003 Harvard study in which scientists were able to trap light.

"At even higher densities, one might expect the material to become a regular, crystalline solid," wrote Professor Clifford Surko, of the University of Californian, San Diego, in an accompanying article.

Taking it one step further, scientists could use the spontaneous annihilation of the BEC, and the subsequent outburst of gamma-rays, to make a powerful laser.

"A gamma-ray laser is the kind of thing that if it existed people would find new uses for it everyday," said Dr Cassidy.

He highlighted an experiment at the National Ignition Facility (NIF) in the US where scientists are using 196 lasers to heat a fuel target to try to kick-start nuclear fusion.

"Imagine doing that but you no longer need hundreds of lasers," he said.

Eh... I'm imagining and I'm not impressed. If we can do it with 196 not very sophisticated lasers, what's the big advantage of doing it with One Big Megamillion Dollar Laser? Who cares how you start it? Keeping it going seems to the be the stickler.

The whole article perplexes me, really, because while you can make a really powerful laser this way, you can also make a really kickin' bomb, and yet they don't discuss that. But this is the BBC, and perhaps they just don't want to frighten their target audience too much.

More: From an old article linked in the BBC sidebar, the laser-fusion connection:

Harnessing nuclear fusion, as the process is known, would offer almost unlimited energy without the release of greenhouse gases such as carbon dioxide.

A proposal to fund the set-up costs of a project called Hiper (High Power Laser Energy Research) is currently being considered by the EU.

...

"In just one cubic kilometre of seawater there is the equivalent energy of the world's oil reserves," says Professor Dunne. "So it's almost limitless fuel."

...

In the core of the Sun, huge gravitational pressure allows this to happen at temperatures of around 10 million Celsius. At the much lower pressures on Earth, temperatures to produce fusion need to be much higher - above 100 million Celsius.

Hiper would achieve these extreme temperatures using ultra powerful lasers - some will concentrate the equivalent of ten thousand times the power of the national grid into a spot less than a millimetre across.

The whole scheme has been drawn up to capitalise on a US project at the National Ignition Facility (NIF) at the Lawrence Livermore National Laboratory in California.

Scheduled for completion in 2010, the massive NIF laser is expected to prove to the world that laser fusion will work and should be taken seriously.

"That will move it from the scientific field to the public and political field," says Professor Dunne.

"Everything from then on is just mere detail - it's technology and engineering."

The NIF laser and Hiper take very different approaches to laser fusion. Professor Dunne compares it to the differences between a diesel and petrol engine.

"Nif is the diesel approach," he says. "You shine lasers at a pellet of material and compress it to such a point that its temperature and density reach a point that allows fusion reactions."

In contrast, Hiper will use two sets of lasers: one to compress the fuel pellet and another, like a spark plug, to ignite it. Using this set up means that the fuel does not need to be compressed as much as it does with NIF, overcoming a major hurdle.

"It's like trying to squeeze jelly," explains Professor Bob Bingham, also of the RAL. "You want to squeeze in a way that it doesn't come back out through your fingers. That really is the key."

I realize scientists are discussing some very heady stuff, but could they take a fucking Learning Annex course on Illuminative Metaphors? "You want to squeeze jelly so it doesn't come out between your fingers"? What?

I'm more confused now. Why the fuck would I want to squeeze jelly in the first place, dickhead? What the blue hell are you talking about dude?

"Well, you see, creating a Bose-Einstein Condensate is sort of like sodomizing a dyspeptic sasquatch with a bucketfull of jellybeans and hatred." Oh, yeah, I totally get it now, thanks for nothin', Poindexter.

posted by Ace at 10:06 PM

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