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Journal Article•DOI•

The National Ignition Facility: enabling fusion ignition for the 21st century

George H. Miller, Edward I. Moses, Craig R. Wuest
01 Dec 2004-Nuclear Fusion (IOP Publishing)-Vol. 44, Iss: 12
TL;DR: The National Ignition Facility (NIF) at Lawrence Livermore National Laboratory, when completed in 2008, will contain a 192-beam, 1.8?MJ, 500?TW, ultraviolet laser system together with a 10?m diameter target chamber and room for 100 diagnostics as discussed by the authors.
Abstract: The National Ignition Facility (NIF) at Lawrence Livermore National Laboratory, when completed in 2008, will contain a 192-beam, 1.8?MJ, 500?TW, ultraviolet laser system together with a 10?m diameter target chamber and room for 100 diagnostics. NIF is housed in a 26?000?m2 environmentally controlled building and is the world's largest and most energetic laser experimental system. NIF provides a scientific centre for the study of inertial confinement fusion and the physics of matter at extreme energy densities and pressures. NIF's energetic laser beams will compress fusion targets to conditions required for thermonuclear burn, liberating more energy than required to initiate the fusion reactions. Other NIF experiments will study physical processes at temperatures and pressures approaching 108?K and 1011?bar, respectively, conditions that exist naturally only in the interior of stars and planets. NIF is currently configured with four laser beams activated in late 2002. These beams are being regularly used for laser performance and physics experiments, and to date nearly 250 system shots have been conducted. NIF's laser beams have generated 106?kJ in 23?ns pulses of infrared light and over 16?kJ in 3.5?ns pulses at the third harmonic (351?nm). A number of target experimental systems are being commissioned in support of experimental campaigns. This paper provides a detailed look at the NIF laser systems, laser and optical performance, and results from laser commissioning shots. We also discuss NIF's high-energy density and inertial fusion experimental capabilities, the first experiments on NIF, and plans for future capabilities of this unique facility.

Summary (3 min read)

Jump to: [1. INTRODUCTION] – [2. THE NIF LASER SYSTEM ARCHITECTURE] – [3. NIF OPTICS] – [4. ACTIVATION OF NIF'S FIRST LASER BEAMS] – [5. EXPANDING SCIENTIFIC HORIZONS USING THE NATIONAL IGNITION FACILITY] – [6. LABORATORY ASTROPHYSICS] – [7. IGNITION ON NIF] – [8. FIRST PHYSICS FROM NIF] and [9. THE PATH FORWARD TO FULL NIF]

1. INTRODUCTION

  • The installation of all 192 ultra-clean and precision aligned beampath enclosures in NIF's two laser bays was completed in September 2003.
  • When completed in 2008, NIF will provide 192 energetic laser beams to compress deuterium-tritium fusion targets to conditions in which they will ignite and burn, liberating more energy than is required from the laser to initiate the fusion reactions.
  • NIF experiments will be conducted in a well-controlled laboratory setting to precisely study physical processes at a range of temperatures and pressures approaching up to 100 million K and 100 billion times atmospheric pressure.
  • The 10-meter diameter target chamber sets the scale for the facility.

2. THE NIF LASER SYSTEM ARCHITECTURE

  • NIF's main laser system consists of two large amplifier units -the power amplifier, and the multi-pass or main amplifier.
  • 3 Experience gained with earlier laser systems at LLNL, e.g., the Shiva 10 kJ infrared laser 26 , and the Nova 30 kJ ultraviolet laser 27 allowed researchers to specify the requirements for the NIF laser architecture.
  • 28 During initial operation, NIF is configured to operate in the "indirect drive" configuration, which directs the laser beams into cones in the upper and lower hemispheres of the target chamber.
  • This configuration is optimized for illuminating the fusion capsule mounted inside cylindrical hohlraums using x-rays generated from the hot walls of the hohlraum to implode the capsule.

3. NIF OPTICS

  • Among the many challenges in designing and building NIF has been the design, engineering, construction, and commissioning of what is arguably the largest precision optical instrument ever built.
  • There are more than 7500 large optics of 40 cm or greater transverse size including laser amplifier glass slabs, lenses, mirrors, polarizers, and crystals.
  • An additional 26,000 smaller optical components are used in NIF.
  • The total area of precision optical surfaces in NIF is nearly 4,000 square meters.
  • Currently NIF's finishing vendors have finished approximately 30% of the optics required for NIF's 192 laser beams.

4. ACTIVATION OF NIF'S FIRST LASER BEAMS

  • In October 2001 the first laser light from NIF's master oscillator was generated in the master oscillator room.
  • This master oscillator has demonstrated the required pulse shaping stability and accuracy for high contrast ignition pulses and other types of laser pulses that are of interest to NIF experimenters.
  • A separate target chamber, known as the Precision Diagnostic System (PDS), which is located in one of NIF's switchyards, has also been used to fully characterize NIF's 1 , 2 , and 3 laser beam energy, power, and wavefront to validate and enhance computer models that predict laser performance.
  • NIF's highest 3 single laser beam energy to date is 10.4 kJ, equivalent to 2 MJ for a fully activated NIF, exceeding the NIF energy point design of 1.8 MJ.
  • High power campaigns have also been completed with drive power reaching 7 terawatts or about 5 gigawatts/cm 2 .

5. EXPANDING SCIENTIFIC HORIZONS USING THE NATIONAL IGNITION FACILITY

  • The National Academy of Sciences in the United States has recently recognized the exciting scientific frontiers becoming available at the next generation of high-energy-density experimental facilities.
  • NIF can explore the physics of matter at temperatures approaching those that existed in the very early universe.
  • 42 NIF's high-energy laser beams can be tailored for driving relatively large, uniform volumes.
  • Currently there is no theory that adequately describes WDM.
  • Isochoric heating with fusion ignition neutrons or high energy petawatt laser-generated ion beams when they become available in the coming decade provides an additional capability for shocking and heating materials to exotic physical states.

6. LABORATORY ASTROPHYSICS

  • Laboratory-based astrophysics experiments, simulating extreme physics phenomena heretofore inaccessible, are now becoming feasible for the first time on NIF.
  • 7 . Radiative shocks such as supernova blast waves can be simulated using scaled gas-filled targets illuminated by energetic laser beams.
  • 49 Figure 8 displays examples of these phenomena and associated laser-driven analog experiments performed on Nova and Omega.
  • Additional examples of scaled astrophysical phenomena that can be simulated using lasers.
  • On the right the visually striking structures seen in the Eagle nebula (Hubble Space Telescope photograph courtesy of NASA STScI, Release Number : STScI-1995-44) are compared with similar RT structures generated using the Nova Laser.

7. IGNITION ON NIF

  • One of the key missions of NIF is to generate and study thermonuclear ignition and energy gain using the 192 lasers of NIF to compress and heat small capsules containing a mixture of the heavy hydrogen isotopes of deuterium and tritium.
  • Precisely focused temporally-shaped laser beams are directed into the hohlraum through the ends and deliver their energy to the inside walls, generating intense x-rays that uniformly illuminate the capsule.
  • 53 Recent studies by LLE researchers are also looking at "polar" direct drive options, in which beam positioning and timing using NIF's indirect drive configuration of lasers can be optimized to directly drive fusion capsules.
  • In addition, significant progress has been made at LANL and at LLE in fabricating smooth and beryllium/copper and plastic capsules that nearly meet these new design specifications.

8. FIRST PHYSICS FROM NIF

  • Over the past year nearly 200 full system shots have been carried out on NIF.
  • In addition a sophisticated suite of experimental diagnostics has been fielded on the 10-meter diameter target chamber and become available for use.
  • The x-ray images compare favorably with sophisticated calculations of laser-plasma interactions.
  • This data is compared with computer models that show qualitative agreement.
  • Two NIF beams were used to drive this experiment, while the other two beams provided separately delayed x-ray backlighter sources.

9. THE PATH FORWARD TO FULL NIF

  • Completion of all 192 laser beams is scheduled for September 2008.
  • The increasing symmetry and energy available as the number of beams increases enables a variety of target configurations including planar targets, horizontal and vertical half-hohlraums , and vertical hohlraums with 4-fold and 8-fold symmetry.
  • After project completion, NIF is expected to ramp up to approximately 700 shots per year for a wide variety of experimental users as a national user facility.
  • As NIF matures, the authors fully expect the facility to evolve to include exciting new capabilities, some of which are mentioned briefly here.

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UCRL-JRNL-206699
The National Ignition Facility:
Enabling Fusion Ignition for the
21st Century
E. I. Moses, G. H. Miller, C. R. Wuest
September 21, 2004
Nuclear Fusion
Disclaimer
This document was prepared as an account of work sponsored by an agency of the United States
Government. Neither the United States Government nor the University of California nor any of their
employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for
the accuracy, completeness, or usefulness of any information, apparatus, product, or process
disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any
specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise,
does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United
States Government or the University of California. The views and opinions of authors expressed herein
do not necessarily state or reflect those of the United States Government or the University of California,
and shall not be used for advertising or product endorsement purposes.
1
The National Ignition Facility: Enabling Fusion Ignition for the 21
st
Century
George H. Miller, Edward I. Moses, Craig R. Wuest
Lawrence Livermore National Laboratory, P.O. Box 808 L-466, Livermore, CA 94551
ABSTRACT
The National Ignition Facility (NIF) at Lawrence Livermore National Laboratory, when completed in
2008, will contain a 192-beam, 1.8-Megajoule, 500-Terawatt, ultraviolet laser system together with a
10-meter-diameter target chamber and room for 100 diagnostics. NIF is housed in a 26,000 square
meter environmentally controlled building and is the world’s largest and most energetic laser
experimental system. NIF provides a scientific center for the study of inertial confinement fusion and
the physics of matter at extreme energy densities and pressures. NIF’s energetic laser beams will
compress fusion targets to conditions required for thermonuclear burn, liberating more energy than
required to initiate the fusion reactions. Other NIF experiments will study physical processes at
temperatures approaching 10
8
K and 10
11
bar; conditions that exist naturally only in the interior of
stars and planets. NIF is currently configured with four laser beams activated in late 2002. These
beams are being regularly used for laser performance and physics experiments and to date nearly 250
system shots have been conducted. NIF’s laser beams have generated 106 kilojoules in 23-ns pulses of
infrared light and over 16 kJ in 3.5-ns pulses at the third harmonic (351 nm). A number of target
experimental systems are being commissioned in support of experimental campaigns. This paper
provides a detailed look the NIF laser systems, laser and optical performance, and results from laser
commissioning shots. We also discuss NIF’s high –energy density and inertial fusion experimental
capabilities, the first experiments on NIF, and plans for future capabilities of this unique facility.
PACS numbers: 42.55.Rz, 42.60.By, 42.60.Jf, 42.60.Lh, 52.38.Dx, 52.57.-z, 52.72.+v, 62.50.+p
1. INTRODUCTION
The National Ignition Facility (NIF), under construction at the Lawrence Livermore National Labora-
tory (LLNL) for the U.S. Department of Energy and National Nuclear Security Administration
(NNSA), provides a scientific center for the study of inertial confinement fusion and the physics of ex-
treme energy densities and pressures. Construction of the building that houses the laser system was
begun in May 1997 and completed in September 2001. The installation of all 192 ultra-clean and pre-
cision aligned beampath enclosures in NIF’s two laser bays was completed in September 2003. In late
2002, NIF began activating its first four laser beamlines. By July 2003, NIF had delivered world-
record single-laser energy performance at its primary wavelength of 1.06 micron, along with record
energy levels at second and third harmonic wavelengths. When completed in 2008, NIF will provide
192 energetic laser beams to compress deuterium-tritium fusion targets to conditions in which they
will ignite and burn, liberating more energy than is required from the laser to initiate the fusion reac-
tions. NIF experiments will be conducted in a well-controlled laboratory setting to precisely study
physical processes at a range of temperatures and pressures approaching up to 100 million K and 100
billion times atmospheric pressure. These conditions exist naturally only in the interior of stars and in
nuclear weapons explosions.
1-5
2
Figure 1. Schematic view of the National Ignition Facility showing the main elements of the laser system. The 10-meter di-
ameter target chamber sets the scale for the facility.
2. THE NIF LASER SYSTEM ARCHITECTURE
Detailed descriptions of NIF’s laser architecture and the performance of the laser system have been
presented recently.
6-21
The NIF laser system is shown in Figure 1. NIF is a highly parallel system of
flashlamp-pumped neodymium-doped phosphate glass lasers. All NIF lasers are driven by the injec-
tion laser system, consisting of a single master oscillator, 48 pulse shaping systems that produce
nanojoule level pulses with arbitrary waveform generation capability, and 48 preamplifier modules
that condition and further amplify the pulses to the joule level prior to injection into the main laser sys-
tem.
NIF’s main laser system consists of two large amplifier units – the power amplifier, and the multi-pass
or main amplifier. The amplifiers, with 16 glass slabs per beam, are arranged with 11 slabs in the main
amplifier section and up to seven slabs per beam in the power amplifier section. Recent optimization
studies indicate that three slabs per beam in the power amplifier are sufficient to meet NIF’s power
and energy requirements, while allowing for additional capability in the future. The amplifiers use 42
kilogram slabs, measuring 46 cm x 81 cm x 4.1 cm, of neodymium-doped phosphate glass set verti-
cally on edge at Brewster’s angle to minimize reflective losses in the laser beam.
22-23
3
A key component in each laser beamline is a plasma-electrode Pockels cell (PEPC), which acts as an
optical switch.
24
When combined with a polarizer, the PEPC allows light to pass through or reflect off
the polarizer. The PEPC thus traps the laser light between two mirrors as it makes four one-way passes
through the main amplifier system before being switched out to continue its way to the target chamber.
The Power Conditioning System located on either side of each laser bay stores up to 500 Megajoules
of electrical energy for the 7,680 flashlamps used in NIF’s large glass amplifier sections.
25
The intense
light from the flashlamps excites the neodymium in the laser slabs to provide optical gain at the pri-
mary 1.06 micron infrared wavelength of the laser.
After passing through the main laser system, each NIF laser beam contains up to approximately 20 kJ
of infrared energy. Laser beams are transported in groups of 4 beams called quads through 10-story
tall “switchyards” in argon-filled beam tubes and directed to the 10-meter target chamber. The NIF
target chamber and final focusing system is designed with maximum flexibility for experimental users
and includes over 100 diagnostic instrumentation and target insertion ports. The NIF Target Bay is ad-
jacent to the Diagnostics Building that houses experimenters, experimenter data acquisition systems,
and target preparation and storage areas. The entire laser system, switchyards, and target area is
housed in an environmentally controlled building that maintains temperature and optical stability as
well as cleanliness protocols external and internal to the laser beampath.
NIF’s laser system architecture was developed following nearly three decades of experience building
large lasers for the U.S. Inertial Confinement Fusion (ICF) Program.
3
Experience gained with earlier
laser systems at LLNL, e.g., the Shiva 10 kJ infrared laser
26
, and the Nova 30 kJ ultraviolet laser
27
al-
lowed researchers to specify the requirements for the NIF laser architecture. These requirements were
driven in part by studies carried out in the late 1980’s and early 1990’s indicating the geometric sym-
metry and amount of laser drive energy needed to uniformly compress, initiate and sustain fusion reac-
tions in spherical deuterium-tritium filled targets using the indirect drive process, which is described
below.
1-2
These requirements taken together with advances in laser technology, including optics and
electro-optical systems led to the NIF conceptual design in 1994.
28
During initial operation, NIF is
configured to operate in the “indirect drive” configuration, which directs the laser beams into cones in
the upper and lower hemispheres of the target chamber. This configuration is optimized for illuminat-
ing the fusion capsule mounted inside cylindrical hohlraums using x-rays generated from the hot walls
of the hohlraum to implode the capsule.
29
In this design, NIF laser beams are directed in an 8-fold
symmetry around the azimuth of the target chamber and arranged in three cones of beams. For inertial
fusion studies the beams will deliver 1.8 million joules (approximately 500 trillion watts of power) in a
specially shaped pulse of laser energy in the near-ultraviolet (351 nanometer wavelength). The pattern
of illumination in the hohlraum target and the sequence of ignition are shown in Figure 2. The energy
available on NIF is approximately 60 times the energy of the Nova laser, which was operated at LLNL
between 1983 and 1999 and currently operating 60-beam Omega Laser at the University of Roches-
ter’s Laboratory for Laser Energetics.
30
Citations
More filters
Journal Article•DOI•

[...]

Ye Zhou1•
Lawrence Livermore National Laboratory1
05 Dec 2017-Physics Reports
TL;DR: In this article, Zhou et al. presented the initial condition dependence of Rayleigh-Taylor (RT) and Richtmyer-Meshkov (RM) mixing layers, and introduced parameters that are used to evaluate the level of mixedness and mixed mass within the layers.
Abstract: Rayleigh–Taylor (RT) and Richtmyer–Meshkov(RM) instabilities are well-known pathways towards turbulent mixing layers, in many cases characterized by significant mass and species exchange across the mixing layers (Zhou, 2017. Physics Reports, 720–722, 1–136). Mathematically, the pathway to turbulent mixing requires that the initial interface be multimodal, to permit cross-mode coupling leading to turbulence. Practically speaking, it is difficult to experimentally produce a non-multi-mode initial interface. Numerous methods and approaches have been developed to describe the late, multimodal, turbulent stages of RT and RM mixing layers. This paper first presents the initial condition dependence of RT mixing layers, and introduces parameters that are used to evaluate the level of “mixedness” and “mixed mass” within the layers, as well as the dependence on density differences, as well as the characteristic anisotropy of this acceleration-driven flow, emphasizing some of the key differences between the two-dimensional and three-dimensional RT mixing layers. Next, the RM mixing layers are discussed, and differences with the RT mixing layer are elucidated, including the RM mixing layers dependence on the Mach number of the initiating shock. Another key feature of the RM induced flows is its response to a reshock event, as frequently seen in shock-tube experiments as well as inertial confinement events. A number of approaches to modeling the evolution of these mixing layers are then described, in order of increasing complexity. These include simple buoyancy–drag models, Reynolds-averaged Navier–Stokes models of increased complexity, including K – e , K–L, and K – L – a models, up to full Reynolds-stress models with more than one length-scale. Multifield models and multiphase models have also been implemented. Additional complexities to these flows are examined as well as modifications to the models to understand the effects of these complexities. These complexities include the presence of magnetic fields, compressibility, rotation, stratification and additional instabilities. The complications induced by the presence of converging geometries are also considered. Finally, the unique problems of astrophysical and high-energy-density applications, and efforts to model these are discussed.

438 citations

Journal Article•DOI•

[...]

John Lindl1, Otto Landen1, John Edwards1, Ed Moses1•
Lawrence Livermore National Laboratory1
28 Feb 2014-Physics of Plasmas
TL;DR: The National Ignition Campaign (NIC) as mentioned in this paper was a multi-institution effort established under the National Nuclear Security Administration of DOE in 2005, prior to the completion of the NIF in 2009.
Abstract: The National Ignition Campaign (NIC) was a multi-institution effort established under the National Nuclear Security Administration of DOE in 2005, prior to the completion of the National Ignition Facility (NIF) in 2009. The scope of the NIC was the planning and preparation for and the execution of the first 3 yr of ignition experiments (through the end of September 2012) as well as the development, fielding, qualification, and integration of the wide range of capabilities required for ignition. Besides the operation and optimization of the use of NIF, these capabilities included over 50 optical, x-ray, and nuclear diagnostic systems, target fabrication facilities, experimental platforms, and a wide range of NIF facility infrastructure. The goal of ignition experiments on the NIF is to achieve, for the first time, ignition and thermonuclear burn in the laboratory via inertial confinement fusion and to develop a platform for ignition and high energy density applications on the NIF. The goal of the NIC was to develop and integrate all of the capabilities required for a precision ignition campaign and, if possible, to demonstrate ignition and gain by the end of FY12. The goal of achieving ignition can be divided into three main challenges. The first challenge is defining specifications for the target, laser, and diagnostics with the understanding that not all ignition physics is fully understood and not all material properties are known. The second challenge is designing experiments to systematically remove these uncertainties. The third challenge is translating these experimental results into metrics designed to determine how well the experimental implosions have performed relative to expectations and requirements and to advance those metrics toward the conditions required for ignition. This paper summarizes the approach taken to address these challenges, along with the progress achieved to date and the challenges that remain. At project completion in 2009, NIF lacked almost all the diagnostics and infrastructure required for ignition experiments. About half of the 3 yr period covered in this review was taken up by the effort required to install and performance qualify the equipment and experimental platforms needed for ignition experiments. Ignition on the NIF is a grand challenge undertaking and the results presented here represent a snapshot in time on the path toward that goal. The path forward presented at the end of this review summarizes plans for the Ignition Campaign on the NIF, which were adopted at the end of 2012, as well as some of the key results obtained since the end of the NIC.

412 citations

Journal Article•DOI•

[...]

Brian Naranjo1, James K. Gimzewski1, Seth Putterman1•
University of California, Los Angeles1
28 Apr 2005-Nature
TL;DR: It is reported that gently heating a pyroelectric crystal in a deuterated atmosphere can generate fusion under desktop conditions and it is anticipated that the system will find application as a simple palm-sized neutron generator.
Abstract: Many methods of reproducing nuclear fusion — the process that powers the Sun — at the table-top scale have been tried, but failed to convince. Remember ‘cold fusion’? More recently, fusion linked to sonoluminescence is still controversial. Now comes a claim from the labs of the University of California at Los Angeles of unequivocal evidence of nuclear fusion in a simple room-temperature experiment. They report that gently heating a pyroelectric crystal — material that becomes charged when heated — causes ionization of a surrounding deuterium gas. The ions bombard a deuterated solid target with such energy that a large neutron signal is detected, a hallmark of deuterium fusion. Though not a viable power source, ‘crystal fusion’ may find application as a generator of neutrons for imaging technology. While progress in fusion research continues with magnetic1 and inertial2 confinement, alternative approaches—such as Coulomb explosions of deuterium clusters3 and ultrafast laser–plasma interactions4—also provide insight into basic processes and technological applications. However, attempts to produce fusion in a room temperature solid-state setting, including ‘cold’ fusion5 and ‘bubble’ fusion6, have met with deep scepticism7. Here we report that gently heating a pyroelectric crystal in a deuterated atmosphere can generate fusion under desktop conditions. The electrostatic field of the crystal is used to generate and accelerate a deuteron beam (> 100 keV and >4 nA), which, upon striking a deuterated target, produces a neutron flux over 400 times the background level. The presence of neutrons from the reaction D + D → 3He (820 keV) + n (2.45 MeV) within the target is confirmed by pulse shape analysis and proton recoil spectroscopy. As further evidence for this fusion reaction, we use a novel time-of-flight technique to demonstrate the delayed coincidence between the outgoing α-particle and the neutron. Although the reported fusion is not useful in the power-producing sense, we anticipate that the system will find application as a simple palm-sized neutron generator.

205 citations

Journal Article•DOI•

[...]

M. J. Edwards, J. D. Lindl, Brian Spears, S. V. Weber, L. J. Atherton, D. L. Bleuel, D. K. Bradley, Debra Callahan, C. J. Cerjan, David C. Clark, Gilbert Collins, James E. Fair, R. J. Fortner, Siegfried Glenzer, S. W. Haan, B. A. Hammel, A. V. Hamza, S. P. Hatchett, Nobuhiko Izumi, B. Jacoby, O. S. Jones, J. A. Koch, B. J. Kozioziemski, Otto Landen, R. A. Lerche, B. J. MacGowan, A. J. Mackinnon, Evan Mapoles, M. M. Marinak, Michael J. Moran, Edward I. Moses, D. H. Munro, D. H. Schneider, Scott Sepke, D. A. Shaughnessy, P. T. Springer, R. Tommasini, L. A. Bernstein, Wolfgang Stoeffl, Riccardo Betti, T. R. Boehly, T. C. Sangster, V. Yu. Glebov, P. W. McKenty, Sean Regan, D. H. Edgell, J. P. Knauer, Christian Stoeckl, D. R. Harding, Steven H. Batha, Gary Grim, Hans W. Herrmann, G. A. Kyrala, Mark D. Wilke, Doug Wilson, Johan Frenje, R. D. Petrasso, K. A. Moreno, H. Huang, K. C. Chen, E. M. Giraldez, J. D. Kilkenny, M. Mauldin, N. Hein, M. Hoppe, A. Nikroo, R. J. Leeper 
01 Jun 2011-Physics of Plasmas
TL;DR: The National Ignition Campaign includes low yield implosions with dudded fuel layers to study and optimize the hydrodynamic assembly of the fuel in a diagnostics rich environment as mentioned in this paper.
Abstract: Ignition requires precisely controlled, high convergence implosions to assemble a dense shell of deuterium-tritium (DT) fuel with ρR>∼1 g/cm2 surrounding a 10 keV hot spot with ρR ∼ 0.3 g/cm2. A working definition of ignition has been a yield of ∼1 MJ. At this yield the α-particle energy deposited in the fuel would have been ∼200 kJ, which is already ∼10 × more than the kinetic energy of a typical implosion. The National Ignition Campaign includes low yield implosions with dudded fuel layers to study and optimize the hydrodynamic assembly of the fuel in a diagnostics rich environment. The fuel is a mixture of tritium-hydrogen-deuterium (THD) with a density equivalent to DT. The fraction of D can be adjusted to control the neutron yield. Yields of ∼1014−15 14 MeV (primary) neutrons are adequate to diagnose the hot spot as well as the dense fuel properties via down scattering of the primary neutrons. X-ray imaging diagnostics can function in this low yield environment providing additional information about the assembled fuel either by imaging the photons emitted by the hot central plasma, or by active probing of the dense shell by a separate high energy short pulse flash. The planned use of these targets and diagnostics to assess and optimize the assembly of the fuel and how this relates to the predicted performance of DT targets is described. It is found that a good predictor of DT target performance is the THD measurable parameter, Experimental Ignition Threshold Factor, ITFX ∼ Y × dsf 2.3, where Y is the measured neutron yield between 13 and 15 MeV, and dsf is the down scattered neutron fraction defined as the ratio of neutrons between 10 and 12 MeV and those between 13 and 15 MeV.

141 citations

Journal Article•DOI•

[...]

M. H. Key
15 Nov 2006-Physics of Plasmas
TL;DR: Fast ignition is an alternate concept in inertial confinement fusion, which has the potential for easier ignition and greater energy multiplication if realized, it could improve the prospects for inertial fusion energy.
Abstract: Fast ignition is an alternate concept in inertial confinement fusion, which has the potential for easier ignition and greater energy multiplication. If realized, it could improve the prospects for inertial fusion energy. It poses stimulating challenges in science and technology, and the research is approaching a key stage in which the feasibility of fast ignition will be determined. This review covers the concepts, the state of the science and technology, the near-term prospects, and the challenges and risks involved in demonstrating high-gain fast ignition.

141 citations

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Journal Article•DOI•

[...]

John Lindl
01 Nov 1995-Physics of Plasmas
TL;DR: In this paper, an approach to fusion that relies on either electron conduction (direct drive) or x rays (indirect drive) for energy transport to drive an implosion is presented.
Abstract: Inertial confinement fusion (ICF) is an approach to fusion that relies on the inertia of the fuel mass to provide confinement. To achieve conditions under which inertial confinement is sufficient for efficient thermonuclear burn, a capsule (generally a spherical shell) containing thermonuclear fuel is compressed in an implosion process to conditions of high density and temperature. ICF capsules rely on either electron conduction (direct drive) or x rays (indirect drive) for energy transport to drive an implosion. In direct drive, the laser beams (or charged particle beams) are aimed directly at a target. The laser energy is transferred to electrons by means of inverse bremsstrahlung or a variety of plasma collective processes. In indirect drive, the driver energy (from laser beams or ion beams) is first absorbed in a high‐Z enclosure (a hohlraum), which surrounds the capsule. The material heated by the driver emits x rays, which drive the capsule implosion. For optimally designed targets, 70%–80% of the d...

1,959 citations

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Proceedings Article•

[...]

Brent C. Stuart1, Michael D. Feit1, Alexander M. Rubenchik1, Bruce W. Shore1, Michael D. Perry1 •
Lawrence Livermore National Laboratory1
21 May 1995
TL;DR: The application of chirped-pulse amplification to shortpulse lasers has led to a dramatic increase in the number of high-power sub-picosecond laser systems.
Abstract: The application of chirped-pulse amplification to short-pulse lasers has led to a dramatic increase in the number of high-power subpicosecond laser systems. Accordingly, knowing the short-pulse damage thresholds of optical components and scaling the damage thresholds with pulse width have become increasingly important.

1,117 citations

Journal Article•DOI•

[...]

Brent C. Stuart1, Michael D. Feit1, Alexander M. Rubenchik1, Bruce W. Shore1, Michael D. Perry1 •
Lawrence Livermore National Laboratory1
20 Mar 1995-Physical Review Letters
TL;DR: A theoretical model based on electron production via multiphoton ionization, Joule heating, and collisional (avalanche) ionization is in good agreement with experimental results.
Abstract: We report extensive measurements of damage thresholds for fused silica and calcium fluoride at 1053 and 526 nm for pulse durations $\ensuremath{\tau}$ ranging from 270 fs to 1 ns. Qualitative differences in the morphology of damage and a departure from the diffusion-dominated ${\ensuremath{\tau}}^{1/2}$ scaling indicate that damage results from plasma formation and ablation for $\ensuremath{\tau}\ensuremath{\le}10$ ps and from conventional melting and boiling for $\ensuremath{\tau}g100$ ps. A theoretical model based on electron production via multiphoton ionization, Joule heating, and collisional (avalanche) ionization is in good agreement with experimental results.

1,045 citations

[...]

J. H. Campbell, T. I. Suratwala
01 Jan 2000
TL;DR: In this paper, the composition and properties of neodymium-doped (Nd-Doped) phosphate glasses used for simultaneous highenergy (10 3 ‐10 6 J) and high-peak power (10 12 10 15 W) laser applications such as fusion energy research, are reviewed.
Abstract: The composition and properties of neodymium-doped (Nd-doped) phosphate glasses used for simultaneous highenergy (10 3 ‐10 6 J) and high-peak-power (10 12 ‐10 15 W) laser applications such as fusion energy research, are reviewed. The most common base glasses are meta-phosphates (O/P3) with the approximate composition: 60P2O5‐10Al2O3‐ 30M2O/MO; K/Ba or K/Mg are typical modifiers. The spectroscopy of Nd 3a in these glasses is well understood and laser properties can be accurately determined from measured spectroscopic properties. The major mechanisms for Nd 3a non-radiative relaxation are reviewed and empirical expressions are presented that predict these eAects in phosphate glasses. Optical and thermal‐mechanical properties have been measured on a number of laser glasses and can be correlated with composition. Sub-critical crack growth rates in stress regions I, II and III have been reported for the first time in phosphate laser glasses. The mechanism for Pt inclusion formation and dissolution has been studied leading to damage resistant (Pt-inclusion-free) laser glasses. ” 2000 Elsevier Science B.V. All rights reserved.

428 citations

"The National Ignition Facility: ena..." refers background in this paper

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Journal Article•DOI•

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John H. Campbell1, Tayyab I. Suratwala1•
Lawrence Livermore National Laboratory1
01 Mar 2000-Journal of Non-crystalline Solids
TL;DR: In this paper, the composition and properties of Nd-doped meta-phosphates are reviewed and the major mechanisms for Nd 3+ non-radiative relaxation are presented and empirical expressions are presented that predict these effects.
Abstract: The composition and properties of neodymium-doped (Nd-doped) phosphate glasses used for simultaneous high-energy (10 3 –10 6 J) and high-peak-power (10 12 –10 15 W) laser applications such as fusion energy research, are reviewed. The most common base glasses are meta-phosphates (O/P ∼3) with the approximate composition: 60P 2 O 5 –10Al 2 O 3 –30M 2 O/MO; K/Ba or K/Mg are typical modifiers. The spectroscopy of Nd 3+ in these glasses is well understood and laser properties can be accurately determined from measured spectroscopic properties. The major mechanisms for Nd 3+ non-radiative relaxation are reviewed and empirical expressions are presented that predict these effects in phosphate glasses. Optical and thermal–mechanical properties have been measured on a number of laser glasses and can be correlated with composition. Sub-critical crack growth rates in stress regions I, II and III have been reported for the first time in phosphate laser glasses. The mechanism for Pt inclusion formation and dissolution has been studied leading to damage resistant (Pt-inclusion-free) laser glasses.

423 citations

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Frequently Asked Questions (21)
Q1. What contributions have the authors mentioned in the paper "The national ignition facility: enabling fusion ignition for the 21st century" ?

NIF provides a scientific center for the study of inertial confinement fusion and the physics of matter at extreme energy densities and pressures. This paper provides a detailed look the NIF laser systems, laser and optical performance, and results from laser commissioning shots. The authors also discuss NIF ’ s high –energy density and inertial fusion experimental capabilities, the first experiments on NIF, and plans for future capabilities of this unique facility. 

In addition to diagnostics, the NIF Program includes support for building and commissioning facility capabilities in diffractive optics (phase plates), cryogenic target systems, and target area operations. 

Beam-to-beam synchronization has also been measured and adjusted to better than 6 picoseconds, which corresponds to approximately 1 part in 150,000 of the total beampath in NIF. 

For inertial fusion studies the beams will deliver 1.8 million joules (approximately 500 trillion watts of power) in a specially shaped pulse of laser energy in the near-ultraviolet (351 nanometer wavelength). 

The Power Conditioning System located on either side of each laser bay stores up to 500 Megajoules of electrical energy for the 7,680 flashlamps used in NIF’s large glass amplifier sections. 

Recent optimization studies indicate that three slabs per beam in the power amplifier are sufficient to meet NIF’s power and energy requirements, while allowing for additional capability in the future. 

The NIF target chamber and final focusing system is designed with maximum flexibility for experimental users and includes over 100 diagnostic instrumentation and target insertion ports. 

NIF experiments will be conducted in a well-controlled laboratory setting to precisely study physical processes at a range of temperatures and pressures approaching up to 100 million K and 100 billion times atmospheric pressure. 

After project completion, NIF is expected to ramp up to approximately 700 shots per year for a wide variety of experimental users as a national user facility. 

Designs supporting indirect-drive, or x-ray drive of ignition capsules in hohraums are becoming more robust as better physics understanding and better modeling capability, including full 3-dimensional modeling of capsules and hohlraums, allows design trade-off studies to be rapidly performed and design spaces to be optimized. 

The 60- beam Omega laser at the University of Rochester Laboratory for Laser Energetics (LLE) is configured to study direct drive ICF and has been performing ignition experiments for many years. 

The capsule is suspended in a hollow gold cylinder called a hohlraum that has laser entrance windows on each end of the cylinder. 

NIF meter-scale optics suitable for high fluence operation with the required wavefront specification are being manufactured at a production rate of over 100 optics per month and the authors are following a schedule for completing production for all the necessary optics for 192 beam lines by 2007. 

A shot campaign conducted on NIF in 2003 provided three target shots per day over a three-day period, giving us confidence in NIF’s ability to meet the planned 700 shots per year when it is fully operational. 

Laser physicists have determined how NIF’s current injection laser, main amplifier, and beam transport system could be modified to allow up to 20 high-energy petawatt-class (HEPW) beams to be directed to target chamber center. 

Other NIF experiments will study physical processes at temperatures approaching 108 K and 1011 bar; conditions that exist naturally only in the interior of stars and planets. 

These designs include extremely narrow micron-diameter fill tubes and graded-dopant beryllium capsules that ease the filling and maintenence of cryogenic DT in the capsule. 

These beams are being regularly used for laser performance and physics experiments and to date nearly 250 system shots have been conducted. 

58 Figure 11 shows recent calculations suggesting that as much as 1.5 MJ of energy may couple to a capsule at 250- eV drive temperature. 

NIF is housed in a 26,000 square meter environmentally controlled building and is the world’s largest and most energetic laser experimental system. 

54A NIF “point design” ignition hohlraum and capsule has been developed using increasingly sophisticated 3D computer calculations.