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Powerful X-ray laser heats solid to 3.6 million degrees

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Powerful X-ray laser heats solid to 3.6 million degrees Powered By Docstoc
					 X-Ray Laser heats up solid to 3.6 million degrees
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.

                             X-Ray Laser
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.

An X-ray laser (or Xaser) is a device that uses stimulated emission to
generate or amplify electromagnetic radiation in the near X-ray or
extreme ultraviolet region of the spectrum, that is, usually on the
order of several of tens of nanometers (nm) wavelength.

Because of high gain in the lasing medium, short upper-state lifetimes
(1–100 ps), and problems associated with construction of X-ray
mirrors, X-ray lasers usually operate without any resonator. The
emitted radiation, based on amplified spontaneous emission, has
relatively low spatial coherence. The line is mostly Doppler broadened,
which depends on the ions' temperature.

As the common visible-light laser transitions between electronic or
vibrational states correspond to energies up to only about 10 eV,
different active media are needed for X-ray lasers.

Lasers fire beams of light that can cut through steel or etch microchip
patterns, depending on the power and wavelength.

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.

      X-Ray Laser Turns Up the Heat to 3.6 Million Degrees
The quest to create nuclear fusion may have come a step closer when
scientists heated solid matter to two million degrees with the world's
most powerful X-ray laser, a study has reported.

A team of researchers working at the SLAC National Accelerator
Laboratory in Menlo Park, California used the rapid-fire laser -- a
billion times brighter that any other man-made X-ray source -- to
flash-heat a miniscule piece of aluminum foil.




The results are being published in the journal Nature.

An x-ray laser fired at a sample of aluminum has generated
temperatures of 3.6 million degrees Fahrenheit — hotter than the
sun’s corona.

Scientists achieved the sizzling temperatures using a powerful x-ray
laser at the SLAC National Accelerator Laboratory. By focusing rapid-
fire pulses from the beam on a piece of aluminum foil thinner than
spider’s silk, they were able to create a material known as hot dense
matter.

The advancement represents the first time researchers have been able
to produce such plasmas in a controlled way.

In so doing, they created a form of plasma known as "hot dense
matter," reaching temperatures hotter than two million degrees
Celsius (3.6 million degrees Fahrenheit), the study reported yesterday
said.

The whole process lasted less than a trillionth of a second.

                           Hot dense matter
Gas-like plasma is often called the fourth state of matter after solids,
liquids and gases. While uncommon on Earth, it makes up over 99
percent of the visible universe, including the interior of stars such as
the Sun.

"Making extremely hot, dense matter is important scientifically if we
are ultimately to understand the conditions that exist inside stars and
at the center of giant planets within our own solar system," said lead
author Sam Vinko, a researcher at the University of Oxford.

Scientists have long been able to create electrically-charged plasma by
heating gases, which can rip away electrons from their atoms.

But up to now no tools existed for doing the same thing at solid
densities that cannot be penetrated by conventional laser beams.

In the experiments, reported in the journal Nature, scientists used
ultra-short wavelengths of X-ray laser light to blast the aluminum foil
and create, for the first time, a uniform patch of plasma, a cube about
one thousandth of a centimetre per side.

The results will be measured against theories and computer
simulations as to how hot, dense matter behaves.

And it should help understand -- and perhaps one day recreate --
nuclear fusion, long heralded as a potentially unlimited and clean
source of energy, the researchers said.
Hot dense matter is some of the most extreme material in the
universe, only existing in the hearts of stars and giant gas planets.
Having a sample of it in the lab should provide insights into the
material, helping scientists to create better models of its behavior.

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