The world's most powerful
laser has heated matter to 10 million Celsius, hotter than the
surface of the Sun.
The Vulcan laser concentrated energy equivalent to 100 times the
world's electricity production into a spot just a few millionths of
a metre across.
Writing in the New Journal
of Physics, scientists said they could create the conditions for
fractions of a second.
The experiments demonstrated concepts which could be key to
building a future nuclear fusion reactor.
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.
"Hiper is a proposed, very large-scale facility and so we have
to check that our understanding is correct," explained Professor
Peter Norreys of the Rutherford Appleton Laboratory (RAL) in
Oxfordshire where the experiments took place.
Extreme condition
Nuclear fusion is looked on as a panacea in a world that demands
ever increasing amounts of energy.
The fuel for the process is deuterium and tritium, two heavier
forms of hydrogen that are commonly found in seawater.
When these isotopes are combined at high temperatures, a small
amount of mass is lost and a colossal amount of energy is
released. By-products are no more radioactive than hospital
waste.
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.
At the much lower pressures on Earth, temperatures to produce
fusion would need to be much higher - above 100 million Celsius.
Ultra powerful lasers, such as Hiper, have been proposed as one
method for reaching these extreme conditions, although many
remain sceptical about the technique.
The project has been drawn up to capitalise on another project
at the National Ignition Facility (NIF) at the Lawrence
Livermore National Laboratory in California.
NIF is expected to demonstrate energy production from laser
driven fusion between 2010 and 2012.
If proven, the technology could rival the current favoured
technique for initiating fusion which uses superconducting
magnets to contain and fuse the hydrogen nuclei.
This
technique will be used in the 10bn-euro
International Thermonuclear Experimental Reactor
(Iter) currently being built in Cadarache,
southern France.
Energy boost
The new work laid some of the foundations for
Hiper.
In the experiments, the Vulcan laser focused one
petawatt (1,000 trillion watts) of power into a
spot about one tenth of the width of a human
hair
The pulse lasted for one picosecond (one
trillionth of a second), heating the target to
10 million Celsius, one tenth of that required
for nuclear fusion.
However, even at these relatively balmy
temperatures, the conditions were equivalent to
these found in supernova explosions.
A special high-speed camera probed the fleeting
moment.
"We wanted to understand the basic interaction
of matter with these laser pulses," Professor
Norreys told BBC News.
Specifically, the team wanted to understand how
much energy was transferred from the laser to
the target.
"Efficient coupling of the laser energy to the
target is crucial for fast ignition fusion, and
is one of the main questions on which the design
of… Hiper depends," said Dr Jonathan Davies from
Instituto Superior Technico, Lisbon, Portugal,
who also took part in the study.
Science and
technology reporter, BBC News
