G

Glossary and Acronyms

GLOSSARY

Ablator: Outermost layer of the target capsule that is rapidly heated and vaporized, compressing the rest of the target.

Adiabat (plasma physics): Determined, for instance, by the ratio of the plasma pressure to the Fermi pressure (the pressure of a degenerate electron gas); used as a measure of plasma entropy.

Blanket: Section of the reactor chamber that serves as the heat transfer medium for the fusion reactor chamber. Some blanket concepts incorporate materials for tritium breeding as well as cooling.

Cryogenic: Involving very low temperatures.

Diode-pumped lasers: Lasers wherein laser diodes illuminate a solid gain medium (such as a crystal or glass).

Direct drive: Inertial confinement fusion (ICF) technique whereby the driver energy strikes the fuel capsule directly.

Driver: Mechanism by which energy is delivered to the fuel capsule. Typical techniques use lasers, heavy-ion beams, and Z-pinches.



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G Glossary and Acronyms GLOSSARY Ablator: Outermost layer of the target capsule that is rapidly heated and vaporized, compressing the rest of the target. Adiabat (plasma physics): Determined, for instance, by the ratio of the plasma pressure to the Fermi pressure (the pressure of a degenerate electron gas); used as a measure of plasma entropy. Blanket: Section of the reactor chamber that serves as the heat transfer medium for the fusion reactor chamber. Some blanket concepts incorporate materials for tritium breeding as well as cooling. Cryogenic: Involving very low temperatures. Diode-pumped lasers: Lasers wherein laser diodes illuminate a solid gain medium (such as a crystal or glass). Direct drive: Inertial confinement fusion (ICF) technique whereby the driver energy strikes the fuel capsule directly. Driver: Mechanism by which energy is delivered to the fuel capsule. Typical tech- niques use lasers, heavy-ion beams, and Z-pinches. 204

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A pp e n d i x G 205 Dry wall: Fusion reactor chamber’s first wall that employs no liquid or gaseous protection. Fast ignition: ICF technique whereby the driver gradually compresses the fuel capsule, followed by a high-intensity, ultrashort-pulse laser that strikes the fuel to trigger ignition. First wall: First surface of the fusion reactor chamber encountered by radiation and/ or debris emitted from the target implosion. These walls may vary in composition and execution such as dry, wetted, or liquid jet. Gain: Ratio of the fusion energy released by the target to the driver energy applied to the target in a single explosion. Heavy-ion fusion: ICF technique whereby ions of heavy elements are accelerated and directed onto a target. High average power: Attribute of a driver that, if repeatable, would make it suitable for an IFE-based power plant. High-energy-density science: Study of the creation, behavior, and interaction of matter with extremely high energy densities. High repetition rate: Maintaining a high rate for engaging the driver or igniting the target, making it suitable for an IFE-based power plant (e.g., 10 Hz). Hohlraum: Hollow container in which an ICF target may be placed, whose walls are used to reradiate incident energy to drive the fuel capsule’s implosion. Hydrodynamic instability: Concept in which fluids of differing physical qualities interact, causing perturbations such as turbulence. Examples include Rayleigh- Taylor and Richtmyer-Meshkov instabilities. Ignition (broad definition): Condition in a plasma when self-heating from nuclear fusion reactions is at a rate sufficient to maintain the plasma’s temperature and fusion reactions without having to apply any external energy. Ignition (IFE): State when fusion gain exceeds unity—that is, when the fusion energy released in a single explosion exceeds the energy applied to the target.

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206 An Assessment of the Prospects for Inertial Fusion Energy Indirect drive: ICF technique whereby the driver energy strikes the fuel capsule indirectly—for example, by the X-rays produced by heating the high-Z enclosure (hohlraum) that surrounds the fuel capsule. Inertial confinement fusion (ICF): Concept in which a driver delivers energy to the outer surface of a fuel capsule (typically containing a mixture of deuterium and tritium), heating and compressing it. The heating and compression then initiate a fusion chain reaction. Inertial fusion energy: Concept whereby ICF is used to predictably and continu- ously initiate fusion chain reactions that yield more energy than that incident on the fuel from the driver for the ultimate purpose of producing electrical power. KD*P: Potassium dideuterium phosphate, a material widely used in frequency conversion optics. Krypton fluoride (KrF) laser: Gas laser that operates in the ultraviolet at 248 nm. Laser–plasma instability: Secondary processes such as symmetry disturbances, fuel preheat, and diversion of laser energy that occur when intense lasers interact with plasmas. Liquid wall: Fusion reactor chamber’s first wall that features thick jets of liquid coolant. This design may also shield the solid chamber walls from neutron damage. Magnetized target fusion: ICF technique whereby a magnetic field is created sur- rounding the target; the field is then imploded around the target, initiating fusion reactions. Mix (plasma physics): When colder target material is incorporated into the hot reaction region of the target, usually as a result of hydrodynamic instabilities. Pulse compression: Technique whereby the incident pulse is compressed to deliver the energy in a shorter time. Pulsed-power fusion: ICF technique that uses a large electrical current to magneti- cally implode a target. Reactor chamber: Apparatus in which the fusion reactions would take place in an IFE power plant. It would contain and capture the energy released from repeated ignition.

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A pp e n d i x G 207 Sabot: Protective device used when injecting an IFE target into the chamber at high speed. Shock ignition: ICF technique that uses hydrodynamic shocks to ignite the com- pressed hot spot. Target: Fuel capsule, together with a holhraum or other energy-focusing device (if one is used), that is struck by the driver’s incident energy in order to initiate fusion reactions. Wall-plug efficiency: Energy conversion efficiency defined as a ratio of the total driver output power to the input electrical power. Wetted wall: Fusion reactor chamber’s first wall that features a renewable, thin layer of liquid. ACRONYMS APG advanced phosphate glass AWE Atomic Weapons Establishment BOP balance of plant CEA Commissariat à l’energie atomique CELIA Centre lasers intenses et applications COE cost of electricity CPA chirped-pulse amplification CPP continuous-phase plate CVD chemical vapor deposition D deuterium DD (drive context) direct drive DEMO demonstration plant DOE Department of Energy DPSSL diode-pumped solid-state laser DT deuterium-tritium ELI Extreme Light Infrastructure ETF engineering test facility FAIR Facility for Antiproton and Ion Research

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208 An Assessment of the Prospects for Inertial Fusion Energy FESAC Fusion Energy Sciences Advisory Committee FLiBe fluorine-lithium-beryllium FTF Fusion Test Facility GDP glow discharge polymer HAPL High Average Power Laser HCX High-Current Experiment HIF heavy-ion fusion HIFTF Heavy-Ion Fusion Test Facility HIF-VL Heavy-Ion Fusion Virtual Laboratory HI-IFE Heavy-Ion Inertial Fusion Energy HiPER High-Power Laser Energy Research HLW high-level waste ICF inertial confinement fusion ID indirect drive IFE inertial fusion energy i-LIFT Laboratory Inertial Fusion Test IRE integrated research experiment ISI incoherent spatial imaging ITER International Thermonuclear Experimental Reactor KDP potassium dihydrogen phosphate LANL Los Alamos National Laboratory LBNL Lawrence Berkeley National Laboratory LDRD laboratory-directed research and development LIFE laser inertial fusion energy LIL Ligne d’Integration Laser LLE Laboratory for Laser Energetics LLNL Lawrence Livermore National Laboratory LLW low-level waste LMJ Laser MégaJoule (project) LPI laser–plasma interactions/instabilities LTD linear transformer driver LULI Laboratoire pour l’utilisation des lasers intenses LWR light water reactor MagLIF magnetized liner inertial fusion MFE magnetic fusion energy

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A pp e n d i x G 209 MTF Magnetized Target Fusion NCDX-II neutralized drift compression experiment II NGNP next-generation nuclear plant NIC National Ignition Campaign NIF National Ignition Facility NNSA National Nuclear Security Administration NRC National Research Council NRL Naval Research Laboratory OFES Office of Fusion Energy Sciences PALS Prague Asterisk Laser System PDD polar direct drive PETAL PETawatt Aquitaine Laser PP pulsed power PPPL Princeton Plasma Physics Laboratory RF radio frequency RTL recyclable transmission line SAC science advisory committee SAL specific activity limit SBS stimulated Brillouin scattering SNL Sandia National Laboratories SRS stimulated Raman scattering SSD smoothing by spectral dispersion T tritium TA technology application TBM test blanket module TPD two-plasmon decay TRL technology readiness level TWAC TeraWatt ACcelerator UV ultraviolet VLT Virtual Laboratory for Technology YAG yttrium-aluminum-garnet