Nuclear Fusion 500 Terawatt Laser at the National Ignition Facility
Δημοσιεύτηκε στις 16 Ιουλ 2012
The
world's most powerful laser system at the National Ignition Facility at
Lawrence Livermore Labs can deliver an ultrashort laser pulse, 5x10^-11
seconds long, which delivers more than 500 trillion watts (terawatts or
TW) of peak power and 1.85 megajoules (MJ) of ultraviolet laser light
to its target.
In context, 500 terawatts is 1,000 times more power
than the United States uses at any instant in time, and 1.85 megajoules
of energy is about 100 times what any other laser regularly produces
today.
The shot validated NIF's most challenging laser
performance specifications set in the late 1990s when scientists were
planning the world's most energetic laser facility. Combining extreme
levels of energy and peak power on a target in the NIF is a critical
requirement for achieving one of physics' grand challenges -- igniting
hydrogen fusion fuel in the laboratory and producing more energy than
that supplied to the target.
The first step in achieving an
experimental fusion reaction is to induce inertial confinement of a
mixture of Deuterium and Tritium (isotopes of hydrogen) at high enough
densities so that their is a self-sustaining reaction. such a reaction
requires a large cross-section of individual nuclei which can only occur
in a high density plasma.
Various methods of achieving this
have included using the Z-Pinch Process to create high energy X-rays to
induce the confinement in fuel pellets,a so-called Z-Machine. Another
fusion method involves using a uniform plasma confined in a collapsing
magnetic field, called a Tokamak or a Toroidal Nuclear Fusion Reactor.
A
lot of experimental results have come from using high energy laser
facilities such as The National Ignition Facility, not only for fusion
physics but also in the test of nuclear weapons eliminating the need for
ground or sea tests of thermonuclear weapons; all the tests can be done
in a laser ignition facility creating minimum effects to the
environment.
For commercial Nuclear Fusion, the Tokamak Design is
the best design for achieving a self-sustaining fusion reaction by
having the toroidal field create a "bottle" of fusion plasma. Such a
reactor would have to be very large to achieve critical mass for
self-sustaining fusion and by far the International Experimental Reactor
(ITER) in France is the best facility for testing the viability of an
energy generating reactor.
Extracting the energy from the
reaction is a different matter and probably will involve the invention
of a high temperature superconducting heat exchanger or confined
superfluid technology to become an efficient source of power.
So
far the best method of heat extraction from a proposed Nuclear Fusion
Reactor Core would be an oxide alloy of a metal with a high
cross-section for gamma rays and a high melting point for absorbed
infrared; hence an alloy of Tungsten dipped into the fusion reactor
plasma is the best form of fusion heat exchanger available with current
technology.
The exploration of other fusion reactions which
utilise fuels easier to access is also another major problem in
developing an efficient fusion reaction, reactions with Helium-3 and
even a man-made Carbon-Nitrogen-Oxygen, CNO, cycle have been proposed.
Even
the use of low-energy muons to catalyse the reaction have been
proposed, though will be probably a long way off until an cost-efficient
muon generator is developed.
In NIF's laser fusion, the lasers
fired within a few trillionths of a second of each other onto a
2-millimeter-diameter target. The total energy matched the amount
requested by shot managers to within better than 1 percent.
The
interesting thing about laser fusion is that, if you make the laser
pulses short enough - on the order of a few hundred attoseconds say, you
could in principle make a laser that would skip electronic transitions
and just manipulate the nuclei of the atoms. This would mean there would
be no blast from the laser itself, just from the nuclear reactions.
This would give the highest efficiency possible of inducing fusion and
the highest level of control, since all of the radiation emitted would
be from the laser pulse.
1999 Nobel Prize in Chemistry was warded for
using femtosecond lasers to observe and control chemical reactions of
individual molecules. Imagine what progress could be done using even
shorter laser pulses to control the nuclear reactions. In the future it
may even be possible to perform subatomic physics with lasers and go
beyond the Schwinger Limit and create any high energy particle we want
from the vacuum. This would replace large accelerators for particle
physics and could allow mass production of some unstable particles for
scientific use.
world's most powerful laser system at the National Ignition Facility at
Lawrence Livermore Labs can deliver an ultrashort laser pulse, 5x10^-11
seconds long, which delivers more than 500 trillion watts (terawatts or
TW) of peak power and 1.85 megajoules (MJ) of ultraviolet laser light
to its target.
In context, 500 terawatts is 1,000 times more power
than the United States uses at any instant in time, and 1.85 megajoules
of energy is about 100 times what any other laser regularly produces
today.
The shot validated NIF's most challenging laser
performance specifications set in the late 1990s when scientists were
planning the world's most energetic laser facility. Combining extreme
levels of energy and peak power on a target in the NIF is a critical
requirement for achieving one of physics' grand challenges -- igniting
hydrogen fusion fuel in the laboratory and producing more energy than
that supplied to the target.
The first step in achieving an
experimental fusion reaction is to induce inertial confinement of a
mixture of Deuterium and Tritium (isotopes of hydrogen) at high enough
densities so that their is a self-sustaining reaction. such a reaction
requires a large cross-section of individual nuclei which can only occur
in a high density plasma.
Various methods of achieving this
have included using the Z-Pinch Process to create high energy X-rays to
induce the confinement in fuel pellets,a so-called Z-Machine. Another
fusion method involves using a uniform plasma confined in a collapsing
magnetic field, called a Tokamak or a Toroidal Nuclear Fusion Reactor.
A
lot of experimental results have come from using high energy laser
facilities such as The National Ignition Facility, not only for fusion
physics but also in the test of nuclear weapons eliminating the need for
ground or sea tests of thermonuclear weapons; all the tests can be done
in a laser ignition facility creating minimum effects to the
environment.
For commercial Nuclear Fusion, the Tokamak Design is
the best design for achieving a self-sustaining fusion reaction by
having the toroidal field create a "bottle" of fusion plasma. Such a
reactor would have to be very large to achieve critical mass for
self-sustaining fusion and by far the International Experimental Reactor
(ITER) in France is the best facility for testing the viability of an
energy generating reactor.
Extracting the energy from the
reaction is a different matter and probably will involve the invention
of a high temperature superconducting heat exchanger or confined
superfluid technology to become an efficient source of power.
So
far the best method of heat extraction from a proposed Nuclear Fusion
Reactor Core would be an oxide alloy of a metal with a high
cross-section for gamma rays and a high melting point for absorbed
infrared; hence an alloy of Tungsten dipped into the fusion reactor
plasma is the best form of fusion heat exchanger available with current
technology.
The exploration of other fusion reactions which
utilise fuels easier to access is also another major problem in
developing an efficient fusion reaction, reactions with Helium-3 and
even a man-made Carbon-Nitrogen-Oxygen, CNO, cycle have been proposed.
Even
the use of low-energy muons to catalyse the reaction have been
proposed, though will be probably a long way off until an cost-efficient
muon generator is developed.
In NIF's laser fusion, the lasers
fired within a few trillionths of a second of each other onto a
2-millimeter-diameter target. The total energy matched the amount
requested by shot managers to within better than 1 percent.
The
interesting thing about laser fusion is that, if you make the laser
pulses short enough - on the order of a few hundred attoseconds say, you
could in principle make a laser that would skip electronic transitions
and just manipulate the nuclei of the atoms. This would mean there would
be no blast from the laser itself, just from the nuclear reactions.
This would give the highest efficiency possible of inducing fusion and
the highest level of control, since all of the radiation emitted would
be from the laser pulse.
1999 Nobel Prize in Chemistry was warded for
using femtosecond lasers to observe and control chemical reactions of
individual molecules. Imagine what progress could be done using even
shorter laser pulses to control the nuclear reactions. In the future it
may even be possible to perform subatomic physics with lasers and go
beyond the Schwinger Limit and create any high energy particle we want
from the vacuum. This would replace large accelerators for particle
physics and could allow mass production of some unstable particles for
scientific use.
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