Friday, May 30, 2008

Scientists heat matter to hotter than surface of the Sun

A laser in Oxfordshire has heated matter to 10 million Celsius, hotter than the surface of the Sun, marking a major landmark in research.The milestone in the field of high energy density physics has been reached by an international team from Japan, the EU and the US working at the Rutherford Appleton Laboratory.
Cleaning a vacuum spatial filter for the Vulcan Petawatt Facility during its construction

Previously only ultra-thin layers of matter (less than one hundredth of a millimetre in thickness) had been heated to similar temperatures and this milestone, where 20 times greater volumes have been heated, takes scientists one step closer to laser fusion, the process that powers the Sun.

The Vulcan laser concentrated power equivalent to 100 times the world's electricity production into a tiny spot for a fraction of a second as part of an effort that will also help scientists to explore many astronomical phenomena in miniature, such as mini-supernovas and tabletop stars.

Writing in the New Journal of Physics, Prof Peter Norreys of the Rutherford and Imperial College London described how the Vulcan laser focused one petawatt of energy (one thousand million million watts) on a spot about one tenth the size of a human hair.

It only lasts for less than 1 picosecond (one millionth of a millonth of a second) but during that time, it is possible to heat materials above their normal melting point - allowing conditions that are found in exotic astrophysical objects such as supernova explosions, white dwarfs and neutron star atmospheres, to be created.

This is the key to the laser's power - it delivers modest energy in a microscopic unit of time. "This is an exciting development - we now have a new tool with which to study really hot, dense matter" says Prof Norreys, whose work is backed by a research council called the STFC.

The Vulcan team has been racing against the $14m Texas Petawatt laser which a few days ago reached greater than one petawatt, making it the highest powered laser in the world, the Titan laser at Lawrence Livermore National Laboratory and the OMEGA EP facility at the University of Rochester, New York.

The UK has proposed an even more powerful laser facility, known as Hiper (High Power laser Energy Research), which will study the feasibility of laser fusion as a potential future energy source.

The scientists hope to use the effort to use lasers to fuse together isotopes of hydrogen, deuterium and tritium, to release a vast amount of energy. The process naturally occurs in the core of the Sun where huge gravitational pressure allows this to happen at temperatures of around 10 million Celsius.

Original here

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