Petawatt Power Peak Reached

The Texas Petawatt laser produced a petawatt of peak power on March 31, making it the highest powered laser in the world, said Todd Ditmire, a physicist at the University of Texas at Austin. The laser is brighter than sunlight on the surface of the sun, but it only lasts for an instant -- a tenth of a trillionth of a second (0.0000000000001 second).

Ditmire said when the laser is turned on, it has the power output of more than 2000 times the output of all power plants in the US. (A petawatt is one quadrillion watts.)

The Texas Petawatt was built with funding provided by the National Nuclear Security Administration. (Photo courtesy University of Texas at Austin)

There has only been one petawatt laser in US history, the Nova laser at Lawrence Livermore Laboratory (LLNL, operated by the University of California for the energy department). Nova, which took up a football field in space, is now defunct. In the past eight or so years, there has been a worldwide push to achieve petawatts (10 to the 15th power). Terawatts (10 to the 12th power) were produced by short pulse lasers in the late 1980s using chirped pulse amplification, the method Ditmire is using.

Ditmire and his colleagues at the Texas Center for High-Intensity Laser Science will use the laser to create and study matter at some of the most extreme conditions in the universe, including gases at temperatures greater than those in the sun and solids at pressures of many billions of atmospheres. This will allow them to explore many astronomical phenomena in miniature. They will create mini-supernovas, tabletop stars and very high-density plasmas that mimic exotic stellar objects known as brown dwarfs.

Todd Ditmire directs the Texas Petawatt project. (Photo courtesy University of Texas at Austin)

“We can learn about these large astronomical objects from tiny reactions in the lab because of the similarity of the mathematical equations that describe the events,” said Ditmire, director of the center.

Such a powerful laser will also allow them to study advanced ideas for creating energy by controlled fusion.

Other US petawatt projects include the OmegaEP laser at the University of Rochester, The Ohio State University petawatt and the Z-Beamlet project at the Sandia National Labs Z-Petawatt Laser Facility. Projects are also underway in the UK, France, Germany, Japan, China and other countries.

The challenge for researchers is to produce a lot of energy in a little time. Producing a petawatt requires generating enough energy in a short enough pulse. The Hercules laser at the University of Michigan (See: Hercules' Power Increased), for example, is only 0.3 petawatts, but it focuses to an incredibly tiny spot. For sheer power -- energy divided by pulse duration -- the Texas petawatt laser now leads the way in the US.

The laser produces a very short duration, very low-energy pulse, and this pulse is stretched in time to a very long pulse, amplified, then finally compressed to a high-energy, super-short-duration pulse. One of the critical aspects of the system is the diffraction gratings used to compress the pulse; made by Jerry Britten's group at LLNL, they are some of the most difficult-to-manufacture optics in the world.

For more information, visit: www.utexas.edu