Thermonuclear ignition in inertial confinement fusion and comparison with magnetic confinement

Betti, R.; Chang, Po-Yu; Spears, B. K.; Anderson, K.S.; Edwards, John; Fatenejad, Milad; Lindl, J. D.; McCrory, R. L.; Nora, R.; Shvarts, D.

doi:10.1063/1.3380857

Cited by 157 publications

(106 citation statements)

References 29 publications

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“…Several forms of a generalized Lawson criterion [9][10][11][12] have been developed to assess progress towards ignition. For ICF, hot spot formation and thermonuclear fuel assembly can be characterized by the neutron yield from primary deuterium-tritium reactions in the central hot plasma, D + T = 4 He(3.5 MeV) + n(14.1 MeV), and the ratio of down scattered to primary neutrons, N (10 − 12 MeV)/N (13 − 15 MeV), quantifying neutrons that have lost energy by scattering processes in the dense fuel plasma that surrounds the central hot plasma.…”

Section: Introductionmentioning

confidence: 99%

Cryogenic thermonuclear fuel implosions on the National Ignition Facility

et al. 2012

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The first inertial confinement fusion implosion experiments with equimolar deuterium-tritium thermonuclear fuel have been performed on the National Ignition Facility. These experiments use 0.17 mg of fuel with the potential for ignition and significant fusion yield conditions. The thermonuclear fuel has been fielded as a cryogenic layer on the inside of a spherical plastic capsule that is mounted in the center of a cylindrical gold hohlraum. Heating the hohlraum with 192 laser beams for a total laser energy of 1.6 mega joules produces a soft x-ray field with 300 eV temperature. The ablation pressure produced by the radiation field compresses the initially 2.2-mm diameter capsule by a factor of 30 to a spherical dense fuel shell that surrounds a central hot-spot plasma of 50 µm diameter. While an extensive set of x-ray and neutron diagnostics has been applied to characterize hot spot formation from the x-ray emission and 14.1 MeV deuterium-tritium primary fusion neutrons, thermonuclear fuel assembly is studied by measuring the down-scattered neutrons with energies in the range of 10 to 12 MeV. X-ray and neutron imaging of the compressed core and fuel indicate a fuel thickness of (14 ± 3) µm, which combined with magnetic recoil spectrometer measurements of the fuel areal density of (1 ± 0.09) g cm −2 result in fuel densities approaching 600 g cm −3 . The fuel surrounds a hot-spot plasma with average ion temperatures of (3.5 ± 0.1) keV that is measured with neutron time of flight spectra. Absolute neutron yields of (7.5 ± 0.1) × 10 14 have been recorded from the magnetic recoil spectrometer and nuclear activation diagnostics while gamma ray measurements provide the duration of nuclear activity of (170 ± 30) ps. These indirect-drive implosions result in the highest areal densities and neutron yields achieved on laser facilities to date. This achievement is the result of the first hohlraum and capsule tuning experiments where the stagnation pressures have been systematically increased by more than a factor of 10 by fielding low-entropy implosions through the control of radiation symmetry, small hot electron production, and proper shock timing. The stagnation pressure is above 100 Gbar resulting in high Lawson confinement parameters of P τ 10 atm s. Comparisons with radiation-hydrodynamic simulations indicate that the pressure is within a factor of three required for reaching ignition and high yield. This will be the focus of future higher-velocity implosions that will employ additional optimizations of hohlraum, capsule and laser pulse shape conditions.

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Section: Introductionmentioning

confidence: 99%

Cryogenic thermonuclear fuel implosions on the National Ignition Facility

et al. 2012

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“…The ratio of alpha particle energy deposited in the hotspot to that generated by fusion ( ) is expected to decrease with perturbation amplitude. This is calculated using a kinetic model of alpha transport [4] in which computational macroparticles interact with the fluid via 'classical' drag and scatter rates [10,11]. The fluid is held stationary; this is necessary to associate a single value of with a single value of the perturbation amplitude.…”

Section: Effect Of Perturbations On Alpha Particle Confinementmentioning

confidence: 99%

“…A similar effect may occur in ICF, preventing the hotspot from maintaining a spherical core with a well-defined 3D radius. This would need to be accounted for in scaling studies such as [3] and [4].…”

Section: Introductionmentioning

confidence: 99%

Effect of perturbations on yield in ICF targets – 4π3D hydro simulations

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et al. 2013

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Abstract. ICF simulations were carried out with the amplitude of perturbations from spherical symmetry treated as a free parameter with the aim of reproducing experimentally observed yields. The simulations began at peak velocity and multi-wavelength perturbations were imposed in the velocity field. It was found that increasing the perturbation caused the gamma bang time to lag behind the xray bang time. Fluid motion broadening of the neutron spectrum was also examined. The effect of perturbation amplitude on alpha particle losses was investigated.

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“…From Newton's law, the hot-spot confinement time is related to the shell inertia like τ ∼ ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi ffi M=4πPR p . Combining these expressions shows that Pτ ∝ v × ρR [4]. This means that a successful ignition experiment must achieve high v and high ρR.…”

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confidence: 99%

“…The conditions necessary for ignition are related to a minimum requirement of the energy density delivered to the DT hot spot and the confinement time of that energy, or equivalently Pτ, the product of the hot-spot pressure (P), a measure of the hotspot energy density, and the energy confinement time (τ) [3]. Betti et al [4] showed that P is related to the implosion velocity (v) by balancing the hot-spot internal energy to the shell kinetic energy via 2πPR 3 ∼ θ 1 2 Mv 2 , where R is the radius of the hot spot, θ is the fraction of the shell kinetic energy converted to hot-spot energy, and M is the mass of the shell. Note that assuming a thin shell results in M ∼ 4πR 2 × ρR; where ρR is the areal density of the imploded shell.…”

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Performance and Mix Measurements of Indirect Drive Cu-Doped Be Implosions

et al. 2015

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The ablator couples energy between the driver and fusion fuel in inertial confinement fusion (ICF). Because of its low opacity, high solid density, and material properties, beryllium has long been considered an ideal ablator for ICF ignition experiments at the National Ignition Facility. We report here the first indirect drive Be implosions driven with shaped laser pulses and diagnosed with fusion yield at the OMEGA laser. The results show good performance with an average DD neutron yield of ∼2 × 10 9 at a convergence ratio of R 0 =R ∼ 10 and little impact due to the growth of hydrodynamic instabilities and mix. In addition, the effect of adding an inner liner of W between the Be and DD is demonstrated. DOI: 10.1103/PhysRevLett.114.205002 PACS numbers: 52.57. Fg, 52.70.La In inertial confinement fusion (ICF) experiments, like those performed at the National Ignition Facility (NIF) [1] and the OMEGA laser facility [2], capsules of deuterium and tritium fuel are imploded to high densities and temperatures to initiate fusion burn. The indirect drive ICF concept uses a laser to irradiate a hohlraum, which produces a nearly uniform thermal x-ray drive. The x-ray drive then ablates the outer capsule material imploding the remaining cryogenically frozen DT shell-mass inward. The conditions necessary for ignition are related to a minimum requirement of the energy density delivered to the DT hot spot and the confinement time of that energy, or equivalently Pτ, the product of the hot-spot pressure (P), a measure of the hotspot energy density, and the energy confinement time (τ) [3]. Betti et al. [4] showed that P is related to the implosion velocity (v) by balancing the hot-spot internal energy to the shell kinetic energy via 2πPR 3 ∼ θ 1 2 Mv 2 , where R is the radius of the hot spot, θ is the fraction of the shell kinetic energy converted to hot-spot energy, and M is the mass of the shell. Note that assuming a thin shell results in M ∼ 4πR 2 × ρR; where ρR is the areal density of the imploded shell. From Newton's law, the hot-spot confinement time is related to the shell inertia like τ ∼ ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi ffi M=4πPR p . Combining these expressions shows that Pτ ∝ v × ρR [4]. This means that a successful ignition experiment must achieve high v and high ρR. In the attempt to achieve these conditions, several ablator materials have been considered, i.e., plastic (CH), high density carbon (HDC), and beryllium. The choice of ablator material has important consequences for the implosion hydrodynamics. For example, the mass ablation rate ( _ m) can be quite different for different materials. Olson et al.[5] measured _ m (in mg=cm 2 =ns) experimentally and found it to be 0.75T 3 r for Be (with and without 1% Cu dopant), 0.50T 3 r for HDC, and 0.35T 3 r for CH (0.6% Ge dopant), where T r is the drive radiation temperature in units of hundreds of eV (or heV). Because the ablation velocity is V a ¼ _ m=ρ, where ρ is the ablator density, Be has the highest V a for the same in-flight ρ. Als...

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Thermonuclear ignition in inertial confinement fusion and comparison with magnetic confinement

Cited by 157 publications

References 29 publications

Cryogenic thermonuclear fuel implosions on the National Ignition Facility

Cryogenic thermonuclear fuel implosions on the National Ignition Facility

Effect of perturbations on yield in ICF targets – 4π3D hydro simulations

Performance and Mix Measurements of Indirect Drive Cu-Doped Be Implosions

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