High-gain, low-intensity ICF targets for a charged-particle beam fusion driver

Sweeney, M. A.; Farnsworth, A. V.

doi:10.1088/0029-5515/21/1/004

Cited by 47 publications

(35 citation statements)

References 30 publications

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“…In MIF, fuel magnetization relaxes the extreme pressure requirements characteristic of traditional ICF and enhances thermal insulation of the hot fuel from the colder pusher [1][2][3][4][5][6][7][8][9][10]. We consider paradigmatically the radial compression of a long, thin cylinder of fuel magnetized with a uniform, axial field prior to compression [11][12][13][14][15][16][17].…”

Section: Pacs Numbersmentioning

confidence: 99%

Understanding Fuel Magnetization and Mix Using Secondary Nuclear Reactions in Magneto-Inertial Fusion

Schmit¹,

Knapp²,

Hansen³

et al. 2014

Phys. Rev. Lett.

113

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Magnetizing the fuel in inertial confinement fusion relaxes ignition requirements by reducing thermal conductivity and changing the physics of burn product confinement. Diagnosing the level of fuel magnetization during burn is critical to understanding target performance in magneto-inertial fusion (MIF) implosions. In pure deuterium fusion plasma, 1.01 MeV tritons are emitted during DD fusion and can undergo secondary DT reactions before exiting the fuel. Increasing the fuel magnetization elongates the path lengths through the fuel of some of the tritons, enhancing their probability of reaction. Based on this feature, a method to diagnose fuel magnetization using the ratio of overall DT to DD neutron yields is developed. Analysis of anisotropies in the secondary neutron energy spectra further constrain the measurement. Secondary reactions are also shown to provide an upper bound for volumetric fuel-pusher mix in MIF. The analysis is applied to recent MIF experiments [M. R. Gomez et al., to appear in PRL] on the Z Pulsed Power Facility, indicating that significant magnetic confinement of charged burn products was achieved and suggesting a relatively low-mix environment. Both of these are essential features of future ignition-scale MIF designs. PACS numbers:Introduction.-Magneto-inertial fusion (MIF) offers some key advantages over traditional inertial confinement fusion (ICF). In MIF, fuel magnetization relaxes the extreme pressure requirements characteristic of traditional ICF and enhances thermal insulation of the hot fuel from the colder pusher [1-10]. We consider paradigmatically the radial compression of a long, thin cylinder of fuel magnetized with a uniform, axial field prior to compression [11][12][13][14][15][16][17]. At stagnation, the compressed magnetic flux redirects charged burn products axially, increasing the effective fuel areal density from ρR to ρZ, where ρ is the fuel mass density, R is the fuel radius, Z is the fuel length, and A ≡ Z/R ≫ 1 is the aspect ratio.Sandia National Laboratories has fielded the first integrated experiments investigating Magnetized Liner I nertial F usion (MagLIF) [14][15][16][17], which involves direct compression of magnetized, preheated deuterium fuel by a solid metal (beryllium) liner, imploded on the 26 MA, 100 ns Z Pulsed Power Facility [18]. The imploding cylindrical liner compresses a pre-seeded axial magnetic field, B 0 (≈ 10 T in the first experiments), to high amplitude at stagnation, B, where perfect flux conservation would imply B = B 0 (R 0 /R) 2 , and R 0 = 2.325 mm is the initial fuel radius. However, detailed simulations suggest that multiple effects (e.g., resistive losses, Nerst effect) can lead to leakage of magnetic flux out of the hot fuel [14,17]. Thus, diagnosing the efficacy of flux compression in experiments is critical for understanding target performance and the viability of the concept.

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Section: Pacs Numbersmentioning

confidence: 99%

Understanding Fuel Magnetization and Mix Using Secondary Nuclear Reactions in Magneto-Inertial Fusion

Schmit¹,

Knapp²,

Hansen³

et al. 2014

Phys. Rev. Lett.

113

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“…The subsequent reduction in the electron thermal conductivity was enough to allow the fuel to reach temperatures high enough to generate a measurable number ͑Ͼ10 contrast, no neutrons could be measured for implosions without fuel magnetization. High yield designs were later proposed for charged-particle beam capsules based on fuel magnetization, 7 but no further experiments were performed.…”

Section: Introductionmentioning

confidence: 99%

Pulsed-power-driven cylindrical liner implosions of laser preheated fuel magnetized with an axial field

Slutz¹,

Herrmann²,

Vesey³

et al. 2010

Physics of Plasmas

533

328

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The radial convergence required to reach fusion conditions is considerably higher for cylindrical than for spherical implosions since the volume is proportional to r2 versus r3, respectively. Fuel magnetization and preheat significantly lowers the required radial convergence enabling cylindrical implosions to become an attractive path toward generating fusion conditions. Numerical simulations are presented indicating that significant fusion yields may be obtained by pulsed-power-driven implosions of cylindrical metal liners onto magnetized (>10 T) and preheated (100–500 eV) deuterium-tritium (DT) fuel. Yields exceeding 100 kJ could be possible on Z at 25 MA, while yields exceeding 50 MJ could be possible with a more advanced pulsed power machine delivering 60 MA. These implosions occur on a much shorter time scale than previously proposed implosions, about 100 ns as compared to about 10 μs for magnetic target fusion (MTF) [I. R. Lindemuth and R. C. Kirkpatrick, Nucl. Fusion 23, 263 (1983)]. Consequently the optimal initial fuel density (1–5 mg/cc) is considerably higher than for MTF (∼1 μg/cc). Thus the final fuel density is high enough to axially trap most of the α-particles for cylinders of approximately 1 cm in length with a purely axial magnetic field, i.e., no closed field configuration is required for ignition. According to the simulations, an initial axial magnetic field is partially frozen into the highly conducting preheated fuel and is compressed to more than 100 MG. This final field is strong enough to inhibit both electron thermal conduction and the escape of α-particles in the radial direction. Analytical and numerical calculations indicate that the DT can be heated to 200–500 eV with 5–10 kJ of green laser light, which could be provided by the Z-Beamlet laser. The magneto-Rayleigh-Taylor (MRT) instability poses the greatest threat to this approach to fusion. Two-dimensional Lasnex simulations indicate that the liner walls must have a substantial initial thickness (10–20% of the radius) so that they maintain integrity throughout the implosion. The Z and Z-Beamlet experiments are now being planned to test the various components of this concept, e.g., the laser heating of the fuel and the robustness of liner implosions to the MRT instability.

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“…It consists of 1) creating of a warm plasma with a closed magnetic field strong enough to reduce electron thermal conduction, 2) operating at lower densities than IFE (but much higher than MFE) in order to reduce radiation losses, and 3) compressing the plasma and embedded field to fusion conditions. [21][22][23][24][25][26][27][28] Early experiments on wall confinement [28,29] and the IFE theory lead to early experiments, [23,24] but later proposed variants [31,32] are based on a field-reversed configuration with a guide field. 1-D & 2-D calculations [4,24,32,33] indicate that both approaches can provide adequate compression of the magnetized plasma, i.e., sufficient to initiate thermonuclear bum.…”

Section: Altering the Fusion Physicsmentioning

confidence: 99%

A Tutorial on Ignition and Gain for Small Fusion Targets

Kirkpatrick¹

2009

AIP Conference Proceedings

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High-gain, low-intensity ICF targets for a charged-particle beam fusion driver

Cited by 47 publications

References 30 publications

Understanding Fuel Magnetization and Mix Using Secondary Nuclear Reactions in Magneto-Inertial Fusion

Understanding Fuel Magnetization and Mix Using Secondary Nuclear Reactions in Magneto-Inertial Fusion

Pulsed-power-driven cylindrical liner implosions of laser preheated fuel magnetized with an axial field

A Tutorial on Ignition and Gain for Small Fusion Targets

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