Europe plans laser-fusion facility
Laser physicists in Europe
have put forward plans to build a 500mil.Pounds facility
to study a new approach to laser fusion. A panel of
scientists from seven European Union countries believes
that a "fast ignition" laser facility could
make a significant contribution to fusion research, as
well as supporting experiments in other areas of physics.
The facility could be up and running by the middle of the
The laser would be used to compress and heat a small
capsule of deuterium and tritium until the nuclei are hot
enough to undergo nuclear fusion and produce helium and
neutrons. In a reactor the energy of the neutrons would
be used to generate electricity without the emission of
greenhouse gases or the generation of long-lived nuclear
The most advanced approach to fusion involves using
magnetic fields to confine the deuterium–tritium plasma.
This is the route to be taken by ITER, which will cost $10bn
to build and run. The alternative "inertial
confinement" technique, which uses lasers or ion
beams rather than magnets to confine the plasma, will be
investigated by the National Ignition Facility (NIF) in
the US and the Laser Mégajoule (LMJ) in France. However,
both these billion-dollar lasers will primarily be used
for nuclear-weapons research, with only 15% of their time
being available for other areas of physics.
In the conventional approach to inertial confinement,
which will be used at NIF and LMJ, the lasers that
compress the fuel capsule also heat it. Fast ignition,
which was first proposed by Max Tabak of the Lawrence
Livermore National Laboratory in the US, relies on
different lasers for these two stages. According to Henry
Hutchinson of the Rutherford Appleton Laboratory in the
UK, who set up the European panel, fast ignition requires
less laser energy than the conventional approach, which
means that it is considerably cheaper.
"The energy problem is sufficiently urgent that we
cannot afford to ignore different approaches to fusion,"
he says. Hutchinson also stresses that any fast-ignition
laser would be a civilian facility, and would be
available for research on astrophysics, atomic physics
and nuclear physics as well.
Fast ignition was first demonstrated at the Gekko XII
laser at Osaka University in Japan in 2001, working with
a team of UK scientists. Kodama and colleagues are now
upgrading their laser system in order to approach "breakeven"
- the point at which the energy output is equal to the
energy needed to sustain the reaction. They then plan to
further enhance their system so that it reaches ignition,
which happens when the fusion reactions generate enough
energy to sustain themselves without the need for further
heating. Finally, they hope to build a demonstration fast-ignition
facility. Physicists in the US are also studying fast
HiPER, as the European proposal is provisionally known,
would be designed to achieve high energy gains, providing
the critical intermediate step between ignition and a
demonstration reactor. It would consist of a long-pulse
laser with an energy of 200 kJ to compress the fuel and a
short-pulse laser with an energy of 70 kJ to heat it.
If Hutchinson and colleagues can persuade research
councils across Europe to back the proposal, construction
could start around the end of the decade. Although the
panel's report does not discuss where the laser should be
built, the UK would be a contender to host the facility.
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