44
PHYSICS Of THE IMPOSSIBLE
lithium deuteride, the active ingredient of a hydrogen bomb). The pellet is usually the size of a pinhead and weighs only 10 milligrams.
The blast of laser light incinerates the surface of the pellet, causing the surface to vaporize and compress the pellet. As the pellet collapses, a shock wave is created that reaches the core of the pellet,
sending temperatures soaring to millions of degrees, sufficient to fuse
hydrogen nuclei into helium. The temperatures and pressures are so
astronomical that "Lawson's criterion" is satisfied, the same criterion
that is satisfied in hydrogen bombs and in the core of stars. (Lawson's
criterion states that a specific range of temperatures, density, and time
of confinement must be attained in order to unleash the fusion process
in a hydrogen bomb, in a star, or in a fusion machine.)
In the inertial confinement process vast amounts of energy are released, including neutrons. (The lithium deuteride can hit temperatures of 100 million degrees centigrade and a density twenty times that
of lead.) A burst of neutrons is then emitted from the pellet, and the
neutrons strike a spherical blanket of material surrounding the chamber, and the blanket is heated up. The heated blanket then boils water,
and the steam can be used to power a turbine and produce electricity.
The problem, however, lies in being able to focus such intense
power evenly onto a tiny spherical pellet. The first serious attempt at
creating laser fusion was the Shiva laser, a twenty-beam laser system
built at the Lawrence Livermore National Laboratory (LLNL) in California that began operation in 1978. (Shiva is the Hindu goddess with
multiple arms, which the laser system design mimics.) The performance of the Shiva laser system was disappointing, but it was sufficient to prove that laser fusion can technically work. The Shiva laser
system was later replaced by the Nova laser, with ten times the energy
of Shiva. But the Nova laser also failed to achieve proper ignition of the
pellets. Nonetheless, it paved the way for the current research in the
National Ignition Facility (NIF), which began construction in 1997 at
the LLNL.
The NIF, which is supposed to be operational in 2009, is a monstrous machine, consisting of a battery of 192 laser beams, packing an
enormous output of 700 trillion watts of power (the output of about
PHYSICS Of THE IMPOSSIBLE
lithium deuteride, the active ingredient of a hydrogen bomb). The pellet is usually the size of a pinhead and weighs only 10 milligrams.
The blast of laser light incinerates the surface of the pellet, causing the surface to vaporize and compress the pellet. As the pellet collapses, a shock wave is created that reaches the core of the pellet,
sending temperatures soaring to millions of degrees, sufficient to fuse
hydrogen nuclei into helium. The temperatures and pressures are so
astronomical that "Lawson's criterion" is satisfied, the same criterion
that is satisfied in hydrogen bombs and in the core of stars. (Lawson's
criterion states that a specific range of temperatures, density, and time
of confinement must be attained in order to unleash the fusion process
in a hydrogen bomb, in a star, or in a fusion machine.)
In the inertial confinement process vast amounts of energy are released, including neutrons. (The lithium deuteride can hit temperatures of 100 million degrees centigrade and a density twenty times that
of lead.) A burst of neutrons is then emitted from the pellet, and the
neutrons strike a spherical blanket of material surrounding the chamber, and the blanket is heated up. The heated blanket then boils water,
and the steam can be used to power a turbine and produce electricity.
The problem, however, lies in being able to focus such intense
power evenly onto a tiny spherical pellet. The first serious attempt at
creating laser fusion was the Shiva laser, a twenty-beam laser system
built at the Lawrence Livermore National Laboratory (LLNL) in California that began operation in 1978. (Shiva is the Hindu goddess with
multiple arms, which the laser system design mimics.) The performance of the Shiva laser system was disappointing, but it was sufficient to prove that laser fusion can technically work. The Shiva laser
system was later replaced by the Nova laser, with ten times the energy
of Shiva. But the Nova laser also failed to achieve proper ignition of the
pellets. Nonetheless, it paved the way for the current research in the
National Ignition Facility (NIF), which began construction in 1997 at
the LLNL.
The NIF, which is supposed to be operational in 2009, is a monstrous machine, consisting of a battery of 192 laser beams, packing an
enormous output of 700 trillion watts of power (the output of about