Glossary of HIF terms
- Ablator
- 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.
- Confinement
- 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
- 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 illumination.
- Dipole
- 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.
- Driver
- 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
- Elise was a scaled-down series of HIF experiments proposed by LBNL in 1996, after the proposal for ILSE was abandoned.
- ETF
- Engineering Test Facility (ETF) would be the final integrated heavy-ion accelerator facility before a full-scale demonstration fusion-energy reactor.
- eV
- 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 second.
- 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.
- HCX
- High-Current Experiment (HCX) is a beam-transport experiment taking a driver-scale 2 MeV beam through a lattice of electrostatic and magnetic quadrupoles.
- IBX
- 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 (IRE).
- ICF
- 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 occur.
- IFE
- 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.
- ILSE
- 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 current.
- 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 eased.
- 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.
- Injector
- The ion source and first stage of acceleration up to 1-2 MeV is the injector of a driver.
- Ion
- 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.
- IRE
- 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 (ETF).
- Lattice
- A sequence of accelerator elements, often periodic, used to focus, accelerate, and bend a beam.
- MBE-4
- 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.
- MFE
- 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
- NIF
- 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.
- NTX
- Neutralized Transport Experiment (NTX) is a scaled experiment using a low-current potassium beam to test many aspects of transport in a fusion chamber.
- Plasma
- 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.
- Quadrupole
- 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 energies.
- SBTE
- 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 electron beams.
- Tokamak
- 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
- 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 years.
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.