

The Navy is pushing ahead with a five-year, $163 million dollar plan to bring the "Holy Grail" of energy weapons up to battlefield strength.

For decades, scientists have been slowly working on a laser that never runs out of shots – and can be "tuned" to blast through the air, at just the right wavelength. For most of that time, all they could get was a laser at lightbulb-strength. But in 2004, researchers at the Thomas Jefferson National Accelerator Facility finally managed to assemble a "Free Electron Laser," or FEL, that could generate 10,000 watts of power. Now, the Navy has started an effort to design and build a new FEL, 10 times as strong. That would bring the laser up to 100 kilowatts – what's considered the minimum threshold for weapons-grade. But it would also be just a stepping stone, on the way to an energy weapon as powerful as any produced. If ray gun researchers can get the thing to work, that is.

Lasers all work in pretty much the same way: Excite certain kinds of atoms, and light particles —

photons — radiate out. Reflect that light back into the excited atoms, and more photons appear. But unlike a lightbulb, which glows in every direction, this second batch of photons travels only in one direction, and in a single color, or wavelength. Which slice of the spectrum depends on the “gain medium” — the type of atoms — you use to generate the beam.

These days, some lasers use use garnet crystals as their gain media. Others, huge vats of toxic chemicals.

But a FEL doesn't use any gain medium at all to generate its beam. It uses a turbocharged stream of electrons to kick-start its reaction, instead. And that lets the FEL

fire along many different wavelengths – and for a long, long time. Which is why it's been called the "Holy Grail of lasers."

The Navy is interested in the FEL because most other lasers lose strength as they move through — and get absorbed by — the atmosphere.

That's especially in moist environments; above the sea, for instance.

But the FEL can pick particular slices of the spectrum where the absorption won't be nearly as bad.

Jefferson Labs researchers showed the world that such weapons might be possible, when their FEL hit the 10 kilowatt mark in 2004. But, in a change of plans, these laser specialists won't be the ones bringing the ray gun up to battlefield strength. Instead, the Navy has asked defense contractors to build the prototype energy weapon, by 2014.

The Navy will issue three, year-long contracts for preliminary designs. From those three, they'll choose two to go into more detailed schematics, and then a single contractor to actually build and test the thing. Total cost: about $163 million, over five years or so. By the end, the Navy wants the device installed on a barge, so it can be tried out at sea.

100 kilowatts should be enough power to zap enemy rockets. And, not that long ago, makers of the next-generation Navy destroyer were talking up the possibility that the ship might be laser-equipped.

But, in what appears to be another shift of direction, the now Navy sees this 100 kw machine primarily as a way to "provide the knowledge that allows scaling with confidence to the MW [megawatt] level in a follow-on device." That would make the FEL as strong as any laser ever built – including the so-called "Nautilus" ray gun, which knocked artillery shells and mortars out of the sky earlier this decade, and the Airborne Laser, designed to blast ballistic missiles.

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