X-Ray Laser Fires Most Powerful Beam Ever

Lasers fire beams of light that can cut through steel or etch microchip patterns, depending on the power and wavelength. Now one team of scientists at the SLAC National Accelerator Laboratory in Menlo Park, Calif., led by Nina Rohringer, has created an X-ray laser that fires more energy, with a more precise wavelength, than any previous model. The results are being published in the journal Nature.

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X-ray lasers are already used in spectroscopy, as a way to look into the depths of molecules like DNA. Back in the 1980s the “Star Wars” missile defense program even floated the idea of X-ray lasers as weapons, powered by nuclear bombs. (The idea was never implemented.) This laser will let scientists see things smaller than ever before.

A laser works by exciting atoms in a crystal, gas or liquid, pushing the electrons nearest to the nucleus into higher energy levels -- a process called “pumping.” When the electrons return to their ground states, neighboring atoms stimulate each other and they emit light of a specific wavelength -- ultimately the laser.

Most lasers, like the ones in CD players and laser pointers, use visible light or electricity to excite the atoms.

But getting a laser beam to work in the X-ray part of the spectrum requires tons of energy. Scientists use particle accelerators to push electrons to near the speed of light and then send them through a set of magnets. The electrons emit laser light in the X-ray spectrum.

But Rohringer’s team at SLAC wanted an even more powerful laser than that, so they used the first laser to pump atoms of neon. Hitting the neon with the beam pushed the electrons closest to the nuclei of the atoms into a high-energy state, and generated a beam with a shorter and more precise wavelength. To get an idea, a visible light laser (like a laser pointer) has a wavelength of a few hundred nanometers. The laser beam in Rohringer's experiment had a wavelength of 1.5 nanometers.

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Laser energies are sometimes measured in electron volts, and this one has a range of 1 eV. Previous X-ray lasers had a range of 8-15 eV. That's important when you want to see what atoms are doing, since the smallest object one can see is limited by the wavelength of the light you use to see it. To look at anything smaller than a few nanometers requires a light beam (a laser in this case) with a wavelength that size, and to get a sharp picture, you also need a well-defined wavelength. Previous X-ray lasers had too much “spread.” The neon laser gets past that limitation, allowing for pictures of smaller and faster phenomena.

Images: Greg Stewart, SLAC (top); SLAC National Accelerator Laboratory (bottom)

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Laser Tests Offer Clue to Magnetic Field Mystery

A shock wave is the only thing needed to create a magnetic field, lab experiments show. An experiment using powerful lasers demonstrated what could happen when a star explodes. The test showed how an exploding star could lead to the creation of magnetic fields.

Gravity may be the master of the universe, but it has had a key assistant in shaping the cosmos -- magnetism. Exactly how that force, which comes from the motion of electric charges, got its start however, has been a mystery -- until now.

A new experiment shows that a relatively simple system that's not initially magnetized can generate magnetic fields out of nothing, said University of Michigan astrophysicist Paul Drake.

"From the standard theories of the Big Bang, you don't start with a strong magnetic field. It has to arise out of what the universe does," Drake told Discovery News.

Working in a laboratory in France, scientists fired high-energy lasers that pulse in a billionth of a second with a trillion times the intensity of sunlight into a helium-filled chamber. The lasers are made of carbon rods, similar to what is found in ordinary pencil lead.

When they pulse, some of the carbon atoms are ripped apart and explode, creating a blast wave that moves out into the gas and generates a magnetic field.

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The process is similar to what happens when a star explodes. It shows one mechanism by which the universe formed and evolved.

Gravity gets the process started, eventually giving rise to collapsing objects that send out shock waves.

"Shocks are the driving force for the formation of magnetic field, and all this precedes galaxy formation," lead researcher Gianluca Gregori, with Oxford University in the United Kingdom, told Discovery News.

Once magnetic fields are established, turbulence takes over, making them larger and sustaining them over the eons.

"It's been rather mysterious that the universe is as magnetized as it," Drake said. "When you do simple calculations, any magnetic field formed in the early phases of the universe one would think should have vanished by now."

Magnetic fields are found everywhere in the universe, even in places where they seemingly shouldn't exist, such as the voids between clusters of galaxies.

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Gravitation is the driving force for the formation of shocks and shocks are the driving force for the formation of magnetic field, and all this precedes galaxy formation," Gregori explained.

Gregori plans to repeat his experiment using the world's largest laser at the Lawrence Livermore National Laboratory in California. It has 10,000 times as much energy as the lasers used in his study.

"If we can use a bigger laser we can drive this shock wave even more powerfully," Gregori said.

"The process that we're investigating now is one possibility (for the origin of magnetic fields), but people have come up with different ideas. The experiments are a tool to guide you to what could be the answer," he said.

The research appears in this week's journal, Nature.

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World's Most Powerful Laser Fires Most Powerful Blast

The world's largest laser was turned on for a fraction of a second. It unleashed the most powerful laser blast in history.

The largest laser in the world was turned on for a fraction of a second last week -- and it unleashed the most powerful laser blast in history.

The National Ignition Facility (NIF) -- a laser test facility at Lawrence Livermore National Laboratory in Livermore, Calif. -- turned on its 192 laser beams for a brief instant on March 15, unleashing a record-setting 1.875-megajoule blast into a target chamber.

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The lasers were combined, gathered and focused through a series of lens into a 2.03-megajoule shot, said Ed Moses, NIF director -- a record for the facility.

That pulse of energy lasted for just 23 billionths of a second, yet it generated 411 trillion watts of power, NIF said -- 1,000 times more than the entire United States consumes at any given instant.

“It’s a remarkable demonstration of the laser from the standpoint of its energy, its precision, its power, and its availability,” Moses told Nature magazine.

But it’s barely half the battle. NIF hopes to dramatically increase the power of the laser shots by the end of year, intending to ultimately use the facility to harness the energy reaction that occurs naturally within the sun: fusion.

“This event marks a key milestone in the National Ignition Campaign’s drive toward fusion ignition,” Moses said.

In fission, atoms are split and the massive energy released is captured. The NIF aims for fusion, the ongoing energy process in the sun and other stars where hydrogen and helium nuclei are continually fusing and releasing enormous amounts of energy. In the ignition facility, beams of light converge on pellets of hydrogen isotopes to create a similar, though controlled, micro-explosion.

As the beams move through a series of amplifiers, their energy increases exponentially. From beginning to end, the beams' total energy grows from one-billionth of a joule to a potential high of four million joules, NIF said -- a factor of more than a quadrillion.

And it all happens in about five millionths of a second.

Because the laser is on for the merest fraction of a second, it costs little to operate -- between $5 and $20 per blast, said spokeswoman Lynda Seaver. But the potential is enormous.

NIF’s managers hope by the end of the year to reach a break-even point, where the energy released is equal to if not greater than the energy that went into the blast.

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“We have all the capability to make it happen in fiscal year 2012,” Moses told Nature.

Experts aren't so sure, citing challenges that NIF and other types of fusion have had in the past.

Glen Wurden, a plasma physicist at Los Alamos National Laboratory in New Mexico, told Nature scientists should be wary of putting all their eggs in the laser basket.

“It’s premature right now,” he told the magazine, citing the troubles that have plagued a competing approach to fusion and its flagship project in France.

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