X-Ray Laser Able to Snap Photos of Electrons
Researchers created this X-ray laser, which fits on a tabletop and is able to visualize electrons.
CREDIT: Tenio Popmintchev, JILA and University of Colorado at Boulder
Superman may make it seem easy, but it's actually difficult to create narrow, directed beams of X-rays. While visible-light lasers have been common for a decade as presentation pointers and cat toys, the first X-ray laser wasn't created until two years ago. Now a team of scientists is announcing today (June 7) that they've created a newer, smaller X-ray laser. It is the first model that fits on a table and doesn't require a miles-long particle accelerator to produce the X-ray beam.
The new tool could help scientists watch tiny phenomena, such as the movements of electrons. Such studies would speed the development of new materials for computing efficiency, green energy and other uses. In the farther future, use of the laser in medical X-ray scans could reduce patients' exposure to radiation, Margaret Murnane, a physicist at the University of Colorado at Boulder and one of the laser's creators, said during a press conference. [Genetically Engineered Cell Shoots Out First-Ever Biological Laser]
Making a narrow X-ray beam requires a large amount of energy, which is why previous X-ray lasers used particle accelerators. To solve that problem, Murnane and her colleagues – including physicists from Austria, Spain and New York state – started with a low-energy infrared laser. They added energy to the infrared photons (the particles that make up light) to make X-rays.
During the process, the laser setup creates flashes of X-rays that last only femtoseconds, or a few millionths of a billionth of a second. Murnane compared the effect to a strobe light, which seems to freeze the movement of people in a room. In this case, the flashes of X-rays are brief enough to freeze the movement of electrons.
For example, the laser is able to visualize how electrons hop around in semiconductor materials. Semiconductor and hard-drive manufacturers have said they're interested, said Henry Kapteyn, a fellow University of Colorado physicist who co-created the new X-ray laser.
X-ray wavelengths are comparable in size to things on the nano-scale, which means structures about a thousandth as wide as a human air. That makes X-rays perfect for observing nano-materials. Stuff that small may have unique properties to better filter water, kill bacteria or increase the efficiency of computers, batteries and solar panels.
"The immediate application that we see for these tabletop X-rays is to understand how the nano-world works," Kapteyn said.
Someday a directed beam of X-rays could produce clearer X-ray images for doctors to analyze, Murnane said. X-ray lasers could render obsolete those heavy lead aprons that people wear during dental X-rays: The rays would be directed only where they're needed instead of inundating the whole body. The lasers also may show up in airport security, Kapteyn said.
One thing that the invention of Murnane, Kapteyn and their colleagues won't be used for is missile defense, they told reporters. The new X-ray laser does not generate nearly enough energy to be useful as a weapon, Kapteyn said.
"We can't blow anything up except for nano-objects," Murnane said.
The researchers said they couldn't guess everything people will use X-ray lasers for in the future. Kapteyn compared the current research environment to the 1960s, when lasers were invented. "After the laser was demonstrated, a lot of people said it was a solution looking for a problem," he said. Lasers are now used in surgery, fiber optics communications, research and more.
The researchers detailed their work in the journal Science.