An Assessment of the Prospects for Inertial Fusion Energy (2013) / Chapter Skim
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2 Status and Challenges for Inertial Fusion Energy Drivers and Targets
2 Status and Challenges for Inertial Fusion Energy Drivers and Targets
Pages 29-88
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From page 29... ...
This discussion of driver approaches is based on input received from proponents who are technical experts in the field.1 As such, the R&D challenges and investment priorities for moving each approach forward to a major test facility -- Fusion Test Facility (FTF) -- are discussed independently of one another -- that is, as if a decision had been made to choose that particular approach as the best option for inertial fusion energy (IFE)
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From page 30... ...
Consequently, shock ignition is usually associated with direct drive. Hot-spot ignition and fast ignition are the main ignition modes for indirect drive.
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From page 31... ...
The greater the convergence ratio3 of the target, the greater the precision required in direct drive -- for example, in drive pressure or shell thick ness. For most laser target designs, this convergence ratio lies between 20 and 40.
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From page 32... ...
To achieve high target energy gain needed for laser inertial fusion energy (IFE) , the rr of the entire fuel, not just the hot spot, must be of the order of 3 g/cm2.
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From page 33... ...
If shock ignition (described below) turns out to be feasible for direct drive but not indirect drive, the difference in gain between direct and indirect drive for a given driver energy will be more pronounced.
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From page 34... ...
Therefore significant amounts of the informa tion learned on laser indirect-drive experiments carry over to indirect drive for ion-driven targets. As for interactions with the chamber wall, direct-drive targets and indirect drive targets have very different output spectra in terms of the fraction of energy in exhaust ions compared to the fraction of energy in X-rays.
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From page 35... ...
With modifications to improve beam smoothness, NIF is also able to study polar direct drive with and without shock ignition.6 Such modifications are estimated to take 4 or more years to complete and cost $50 million to $60 million (including a 25 percent contingency added by this committee; see Chapter 4) .7 In summary, both direct drive and indirect drive have advantages.
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From page 36... ...
The minimum ignition energy, Eig, is independent of target size and scales only with the density of the target; the greater the mass density, the less the beam energy required for ignition (about 20 kJ of collimated electron/ion beam energy is required for a ~300 g/cm3 fuel assembly) .12 The optimum compressed-fuel configuration for fast ignition is an approxi mately uniform-density spherical assembly of high-density DT fuel without a cen tral hot spot.
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From page 37... ...
SOURCE: H Azechi, Osaka University, "Inertial Fusion Energy: Activities and Plans in Japan," Presentation to the committee on June 15, 2011.
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From page 38... ...
Zalasek, and D.E. Fyfe, 2010, Shock ignition target design for inertial fusion energy, Physics of Plasmas 17: 042701.
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From page 39... ...
While there is considerable experimental information at scale sizes that are too small to achieve ignition and burn, these instabilities are an important concern for both direct drive and indirect drive for fusion-scale targets, especially because the available experimental data are limited. Furthermore, the instabilities become more deleterious with increasing wavelength and increasing laser intensity.
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From page 40... ...
. ignition using laser indirect drive is not likely in the next several years."19 In the same place, it also states that "resolving the present issues and addressing any new challenges that might arise are likely to push the timetable for ignition to 2013-2014 or beyond." The panel goes on to also conclude as follows: • If ignition is achieved with indirect drive at NIF, then an energy gain of 50-100 should be possible at a future facility.
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From page 41... ...
The program on NIF should be expanded to include direct drive and alternate modes of ignition. It should aim for ignition with moderate gain and comprehensive scientific understanding leading to codes with predictive capabilities for a broad range of IFE targets.
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From page 42... ...
From a fuel-capsule standpoint, the status and issues are the same as those discussed above for laser indirect drive. The principal new ques tions are these: • Can one correctly predict the range of intense ion beams in hot matter?
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From page 43... ...
Unfortunately, there is no experi mental information on ion direct drive. Ion-Driven Fast Ignition The earliest targets for heavy-ion fusion, described in the mid-1970s, were based on fast ignition using intense ion beams.27 Imploding the fuel using ion beams and igniting it with a laser is another option.
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From page 44... ...
Pulsed-Power Targets Historically, both indirect drive and ion- and electron-driven direct drive have been studied for pulsed-power inertial fusion. Many of the considerations discussed above for laser and heavy-ion targets also apply to these classes of pulsed-power targets.
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From page 45... ...
As noted in the preceding section, the technical approaches to achieving inertial fusion energy include three kinds of drivers: lasers, heavy-ion accelerators, and elec trical pulsed-power systems. As discussed below, good progress has been made in developing the repetitively pulsed systems required for fusion energy.
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From page 46... ...
A recently published handbook provides an overview of the status of high-power lasers, including chapters on the NIF laser, the KrF laser, and on high-power diode arrays for pumping high-average-power, solid-state lasers.30 Projected Target Gains Ignition and gain with indirect drive are presently being pursued in the NIF, following decades of research on earlier laser systems such as Nova.31 Computa tions at LLNL suggest that in a power plant, reactor-scale target gains of ≥60 might be attainable with optimized indirect-drive targets driven by 2 MJ of 3w32 light.33 Direct-drive targets are also being considered. Their designs evolved from work at the University of Rochester's LLE and the Naval Research Laboratory (NRL)
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From page 47... ...
Colombant, J.L. Giuliani, et al., 2010, The science and technologies for fusion energy with lasers and direct-drive targets, IEEE Transactions on Plasma Science 38: 690.
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From page 48... ...
The scale of the laser energy required for an indirect-drive or direct-drive IFE power plant is likely to be comparable to the NIF laser -- i.e., ~2 MJ per pulse in the ultraviolet but operated at 5 to 15 pulses per second repetition rate. Although a DPSSL driver can be used to drive either direct-drive or indirect-drive targets, this section describes a DPSSL-driven IFE power plant based on indirect drive because that approach is more mature and has been studied in the NIF-driven target experiments in depth.
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From page 49... ...
S tat u s & C h a l l e n g e s for Inertial Fusion Energy Drivers & Targets 49 FIGURE 2.5 (a) Isometric view of a proposed laser-driven IFE power plant showing compact beam architecture composed of 384 lasers.
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From page 50... ...
Aceves, T Anklam, et al., 2011, "Compact, efficient laser systems required for laser inertial fusion energy," Fusion Science and Technology 60: 28-48.
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From page 51... ...
Aceves, T Anklam, et al., 2011, Compact, efficient laser systems required for laser inertial fusion energy, Fusion Science and Technology 60: 28-48.
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From page 52... ...
Aceves, T Anklam, et al., 2011, Compact, efficient laser systems required for laser inertial fusion energy, Fusion Science and Technology 60: 28-48.
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From page 53... ...
SG-III laser, which will operate frequency-tripled (like the NIF) at 351 nm for inertial confinement fusion experiments with 48 beams at 3 ns and 200 kJ total energy.
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From page 54... ...
It should be tested to determine that it can meet the hot-swap requirements for a line-replaceable unit. Path Forward for Diode-Pumped Solid-State Laser-Based Inertial Fusion Energy In this section, the integrated systems engineering and supporting R&D required to develop a solid-state, laser-driven IFE power plant is described.
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From page 55... ...
Aceves, T Anklam, et al., 2011, Compact, efficient laser systems required for laser inertial fusion energy, Fusion Science and Technology 60: 28-48.
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From page 56... ...
Conclusion 2-2: If the diode-pumped, solid-state laser technical approach is selected for the roadmap development path, the demonstration of a diode pumped, solid-state laser beam-line module and line-replaceable-unit at full scale is a critical step toward laser driver development for IFE. Conclusion 2-3: Laser beam delivery to the target via a UV beam line, the final optics components, and target tracking and engagement are critical technologies for laser-driven inertial fusion energy.
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From page 57... ...
Aceves, T Anklam, et al., 2011, Compact, efficient laser systems required for laser inertial fusion energy, Fusion Science and Technology 60: 28-48.
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From page 58... ...
The third step, referred to as LIFE 3 power plant design, captures the improvements gained from LIFE 2 operation and provides insight into the economics for the commercial power plant operation.
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From page 59... ...
Because inductance slows the rise of high-current electron beams and the excimer upper-state radiative lifetime is only on the order of 1 ns in typical conditions, the "angular multiplex" architecture was proposed67 to compress electron beam energy delivered in several hundred nanoseconds down to a laser fusion driver pulse of few nanoseconds. The multiplex architecture passes many sequential copies of the desired drive pulse through the electron-beam pumped medium, extracting all of the energy, before the copies are time-shifted to all arrive simultaneously at the target.
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From page 60... ...
Sethian et al., 2010, The science and technologies for fusion energy with lasers and direct drive targets, IEEE Transactions on Plasma Science 3: 690-703. and supported with modeling at a scale to support KrF as a technical application approach for an IFE laser driver.
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From page 61... ...
Obenschain, "Krypton Fluoride Laser Driven Inertial Fusion Energy," Presentation to the committee on January 29, 2011.
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From page 62... ...
Giuliani, and A.J. Schmitt, 2009, Pulse shaping and energy storage capabilities of angularly-multiplexed KrF laser fusion drivers, Journal of Applied Physics 106: 023103, and references therein.
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From page 63... ...
Giuliani, and A.J. Schmitt, 2009, Pulse shaping and energy storage capabilities of angularly-multiplexed KrF laser fusion drivers, Journal of Applied Physics 106: 023103, and references therein.
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From page 64... ...
Sethian et al., 2010, The science and technologies for fusion energy with lasers and direct drive targets, IEEE Transactions on Plasma Science 38(4)
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From page 65... ...
Obenschain, NRL, "Krypton Fluoride Laser Driven Inertial Fusion Energy," Presentation to the committee on January 29, 2011. targets may be studied initially with 1-steradian segments of target and a single 20 kJ module as proposed below by the NRL (Figure 2.7)
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From page 66... ...
Phase II would consist of a full-size KrF laser beam line (20 kJ at 5 Hz) along with other inertial fusion energy components.
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From page 67... ...
Heavy-Ion Accelerators Background and Status The U.S. Department of Energy supported the development of heavy-ion accelerators for fusion power production until 2003, and it funded several concep tual power plant designs for both accelerator and laser drivers.
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From page 68... ...
The most recent two-dimensional simulations of indirectly driven targets, carried out by LLNL, showed better performance than the target used for the con ceptual power plant design. Specifically, the simulations indicated that it would be possible to achieve gains on the order of 90 to 130 at beam energies from 1.8 to 3.3 MJ, respectively.92 The two-dimensional codes used were the same as those used for laser drivers, but the X-rays were produced when the ion beams hit material inside the hohlraum rather than the hohlraum walls, as with laser beams.
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From page 69... ...
Abbott, et al., 2003, An updated point design for heavy ion fusion, Fusion Science and Technology 44: 266-273; DOE, 1992, OSIRIS and SOMBRERO Inertial Fusion Power Plant Designs, Final Report, DOE/ER/54100; DOE, 1992, Inertial Fusion Energy Reactor Design Studies, PROMETHEUS-L and PROMETHIUS-H, Final Report, DOE/ER/54101. More recent design studies that have been reviewed as rigorously as those cited here do not exist in this case.
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From page 70... ...
Although the cost reduction program and other parts of the program aimed at fusion energy were discontinued in 2003, accelerator development was fortunately able to continue at a modest budget level in support of high-energy-density physics research. Most recently, Recovery Act funds have allowed the construction of the NDCX-II accelerator.
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From page 71... ...
• Optimizing plasma source development technology for intense ion-beam pulse compression and focusing. • Raising the beam energy from ~1 J to ~100 kJ per beam.
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From page 72... ...
• Demonstrating technologies needed to produce repetitively cycled liquid walls. The committee notes as follows: • While the base case considered for HIF uses an induction linac, indirect drive, and thick liquid walls, other options are possible, such as polar direct drive, shock ignition, and thin liquid or solid walls.
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From page 73... ...
Conclusion 2-7: Demonstrating that the Neutralized Drift Compression Experiment-II (NDCX-II) meets its energy, current, pulse length, and spot size objectives will be of great technical importance, both for heavy-ion inertial fusion energy applications and for high-energy-density physics.
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From page 74... ...
Assess the need for radiation-resistant plasma sources. • Do a power plant study of the reference ≥3 MJ target approach for a liquid wall chamber.
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From page 75... ...
Moreover, for indirect drive, the physics of the fuel capsule itself is largely independent of the source of the X-rays used to drive the fuel cap sule as long as the X-rays have the correct spectrum (approximately thermal) , time dependence, and symmetry.
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From page 76... ...
In contrast, much of the needed accelerator technology has been developed for nuclear and particle physics and, in the case of induction accelerators, for radiography and other 110 See A.W. Maschke, 1975, Relativistic ions for fusion applications, Proceedings of the 1975 Particle Accelerator Conference, Washington, D.C., IEEE Transactions on Nuclear Science NS-22 (3)
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From page 77... ...
The proposed HIF Ignition Test Facility will initially be built without all the power supplies needed for high-repetition rate operation. At this point, it will be used to refine and validate those aspects of target physics that have not yet been tested at full scale.
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From page 78... ...
115 See, for example, J.P. VanDevender, 1986, Inertial confinement fusion with light ion beams, Plasma Physics and Controlled Fusion 28: 841-855.
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From page 79... ...
ignition of magnetized fusion fuel -- MagLIF -- and recent favorable com puter simulation results for this concept have caused MagLIF to become a leading candidate for pulsed-power fusion energy.118 Imploding a magnetized, field-reversed target plasma in a solid or liquid liner by a pulsed external magnetic field is a 1970s (or earlier) idea that has been pushed from the millisecond to the microsecond timescale in the present embodiment, MTF.119 This approach is very properly described as a hybrid of magnetic and inertial confinement fusion, since the magnetic field configuration is a closed confinement geometry.
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From page 80... ...
Cipiti, et al., Z-inertial fusion energy: Power plant final report FY06, Sandia National Laboratories report SAND2006-7148.
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From page 81... ...
Thus, the major target physics challenges that are to be addressed in the near term on Z are the following: • Demonstrating that the predicted high-efficiency energy transfer from electrical energy to hot magnetized fusion fuel plasma compressed by magnetic-field-driven implosion of a cylindrical conducting liner occurs in experiments. Determining plasma conditions inside the imploding liner is a major part of this challenge.
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From page 82... ...
Rodriguez, C.O. Farnum, et al., 2006, Z-inertial fusion energy: Power plant, SAND2006-7148.
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From page 83... ...
Fowler, A.A. Kim, et al., 2009, High current, 0.5-MA, fast, 100-ns, linear transformer driver experiments, Physical Review Special Topics-Accelerators and Beams 12: 050401.
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From page 84... ...
inertial confinement fusion program. Recommendation 2-2: Physics issues associated with the Magnetized Liner Inertial Fusion (MagLIF)
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From page 85... ...
• Target physics. Using existing facilities, validate the magnetically imploded cylindrical target concept to the point of achieving scientific breakeven (fusion energy out = energy delivered to the fuel)
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From page 86... ...
New funding between $8 million and $10 million per year is needed to under take the last four engineering development tasks.132 Medium Term (5-15 Years, Assumes All Milestones in Phase 1 Are Achieved) • Target physics: Ignition.
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From page 87... ...
6, received March 24, 2011. • Target design and fabrication for inertial fusion energy.
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From page 88... ...
These approaches involve three kinds of targets: indirect drive, direct drive, and magnetized target. In addition, the chamber may have a solid or a thick-liquid first wall that faces the fusion fuel explosion, as discussed in Chapter 3.
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