Glossary of HIF terms
- An ablator is the outer portion of a fuel pellet
that is used to implode the fuel in the reaction chamber.
The ablator is rapidly heated by the driver beams, and as
it evaporates outwards, momentum conservation forces the
contained fuel to implode (a "rocket" effect). This
implosion increases the density of the fuel reactants by as
much as a factor of 1000.
- In order for significant thermonuclear energy
production, the fuel must remained confined for a
sufficiently long time (at both a high enough temperature
and density) so that a large number of nuclear fusion
reactions will occur. For inertial confinement, this
time is less than a nanosecond. For the magnetic
confinement, this time ranges from seconds to an
eventual goal of hours.
- Deuterium is a naturally occurring isotope of
hydrogen that contains one proton and one neutron. It and
tritium, another hydrogen isotope with two neutrons, have a
large fusion reaction cross-section which results in end
products of one helium nucleus and one neutron with
combined kinetic energies of 17.6 MeV.
- Direct drive
- The inertial fusion target is directly driven by energy
from the fusion driver. That is the power from the driver
couples directly to the surface of the fuel capsule.
Although more efficient, this form of target coupling
requires very precise beam aiming and uniform target
- A device for deflecting the path of the beam. A
magnetic dipole field bends the path charged particles (or
beams of charged particles) with a force proportional to
their velocity, the strength of the field, and the charge
of the particles. An electric dipole field bends with a
force proportional to the strength of the field and the
charge of the particles.
- The term driver is the name given to the
apparatus that produces the required laser or ion beams and
which directs them at the fuel pellet in an inertial
confinement fusion reactor chamber.
- Electrostatic quadrupole
- See Quadrupole
- Elise was a scaled-down series of HIF experiments
proposed by LBNL in 1996, after the proposal for ILSE was
- Engineering Test Facility (ETF) would be the
final integrated heavy-ion accelerator facility before a
full-scale demonstration fusion-energy reactor.
- Electron-Volt is a unit of energy used in particle and
atomic physics representing the energy given to an electron
accelerated though a one Volt potential difference. One
eV is equivalent to 1.9x10-19 Joules. One
keV is 1000 eV, one MeV is one-million eV, while one GeV is
one-billion eV. The energy of one photon of visible light
is about 1.7 eV. A typical power plant produces 1 GW of
electrical power, which is 1 billion Joules per
- Final focus
- The last focusing elements of a driver which reduce the
beam size from several centimeters in radius to about 3
millimeters in radius at the fusion fuel target is referred
to as the final focusing system.
- High-Current Experiment (HCX) is a
beam-transport experiment taking a driver-scale 2 MeV beam
through a lattice of electrostatic and magnetic
- Integrated Beam Experiment (IBX) is being
considered to link together the present high-current
experiments, thereby providing some of the science base
needed to design a larger Integrated Research Experiment
- Inertial Confinement Fusion (ICF) is the
approach to controlled thermonuclear fusion which uses
intense ion or laser beams to implode and ignite target
pellets of deuterium-tritium fuel, whose inertia confines
them for a sufficiently long time for a good "burn" to
- Inertial Fusion Energy (IFE) is the name for the
research program in the U.S. Department of Energy whose
goal is to use the ICF approach to controlled thermonuclear
fusion energy to commercial power production.
- The Induction Linac Systems Experiments (ILSE)
was a proposal by the LBNL HIF group to build a
10-MeV multiple-beam accelerator that was to have modeled
an ICF ion driver on a small scale but with several
driver-scale characteristics, such as beam size and
- Indirect drive
- The inertial fusion target is indirectly driven by
energy from the fusion driver. That is the power from the
driver is first converted to x-rays inside a type of oven
called a "hohlraum". The fuel capsule placed inside the
hohlraum is driven by the x-rays. Due to the inefficiency
of the conversion to x-rays, three to four times more
energy is required from the driver but the requirements on
aiming precision and illumination uniformity are greatly
- Induction linac
- Induction linac is the name given to a type of
linear accelerator which accelerates charged particles by
using the electric field produced by a rapidly-changing
magnetic field strength in a ferrromagnetic core. Induction
linacs are useful wherever relatively large (> 1
kiloamp) beam currents must be accelerated.
- The ion source and first stage of acceleration up to
1-2 MeV is the injector of a driver.
- An ion is an atom has lost (or occasionally
gained) one or more electrons and thus has a net electrical
charge. An plasma is said to be fully ionized if its atoms
have completely loss their bound electrons.
- Integrated Research Experiment (IRE) is
conceived as an intermediate-scale device, combining a
multiple-beam injector, eletrostatic and magetic transport
lattices, acceleration, longitudinal confinement, steering,
compression, final focusing, and chamber transport.
The experiment would provide the science basis for
designing a larger Experimental Test Facility
- A sequence of accelerator elements, often periodic,
used to focus, accelerate, and bend a beam.
- The Multiple Beam Experiment (MBE-4) at LBNL
refers to a accelerator which examined the physics of the
acceleration and controlled transport of four parallel
cesium ion beams at the same time. MBE-4, whose total
energy (900 kEV) was much greater than SBTE, produced
additional understanding of the beam dynamics of
space-charge dominated beams.
- Magnetic Fusion Energy (MFE) is the approach to
controlled thermonuclear energy which uses magnetic fields
to confine a hot, but rarefied thermonuclear fuel. A
tokamak is an example of a device that operates upon the
principles of magnetic confinement.
- Magnetic quadrupole
- see Quadrupole
- National Ignition Facility (NIF) is a large
proof-of-principle experiment at the Lawrence Livermore
National Laboratory using 192 neodymium-glass laser to
ignite an inertial-fusion target.
- Neutralized Transport Experiment (NTX) is a scaled
experiment using a low-current potassium beam to test many
aspects of transport in a fusion chamber.
- The so-called fourth state of matter, a plasma
is an ensemble of ionized particles which are not
chemically bonded together. A plasma may be electrically
neutral (as in the core of the Sun or ICF fuel pellet) or
have a net charge (as is true of a beam in an accelerator).
In general, the temperatures necessary for fusion imply
that burning fuel is in a plasma state.
- A quadrupole is the name given to a force field
produced by four individual poles, two positive and two
negative. Quadrupoles may use either electric or magnetic
fields. Quadrupole fields are often used to focus and help
transport charged particle beams in accelerators. For
heavy-ion fusion accelerators, electrostatic quadrupoles
are typically employed for low-energy transport (< 20
MeV), and magnetic quadrupoles are used at higher
- The Single Beam Transport Experiment (SBTE) at
LBNL examined fundamental physics of transporting a low
energy (200-keV) but space-charge dominated cesium ion
beam. Results from SBTE showed that beams could be
transported without significant degradation of beam quality
even when the space-charge pressure exceeded the thermal
pressure by factors of ten or more.
- Space-charge-dominated beams
- A beam of charged particles is said to be
space-charge dominated when the effective electrical
force of repulsion of the like charges is stronger than the
pressure associated with the internal temperature of the
beam. Usually, this concept applies to
non-relativistic ion beams, since the repulsive
space-charge force is normally almost completely canceled
by the attractive self-magnetic force in relativistic
- A tokamak is the Russian name given to a large,
doughnut-shaped fusion device that is surrounded by
electrical coils which produce intense magnetic fields to
confine a hot, D-T fuel plasma.
- Tritium is an isotope of hydrogen that contains
one proton and two neutrons. It and deuterium (see above)
have a large thermonuclear fusion cross-section. It is also
radioactive with a half-life of approximately 12.5
For comments or questions contact WMSharp@lbl.gov or DPGrote@lbl.gov. Work
described here was supported by the Office of Fusion Energy
at the US Department of Energy under contracts
DE-AC03-76SF00098 and W-7405-ENG-48. This document was
last revised June, 2001.