Ignition target design and robustness studies for the National Ignition Facility

Krauser, William J.; Hoffman, N. M.; Wilson, D. C.; Wilde, B. H.; Varnum, W. S.; Harris, David B.; Swenson, Fritz J.; Bradley, P. A.; Haan, S. W.; Pollaine, S. M.; Wan, A.; Moreno, Juan Carlos; Amendt, Peter

doi:10.1063/1.872006

Cited by 99 publications

(52 citation statements)

References 19 publications

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“…According to simulations, capsule designs using a Be ablator also require doping (e.g., with Cu) in order to achieve optimum performance. Currently, these Be ablator capsule designs span several peak x-ray drive temperatures and total laser energies: 330 eV/1.3 MJ (Krauser et al 1996), 300 eV/1.3 MJ (Dittrich et al 1996), 250 eV/900 kJ ), 280 eV/1.4 MJ , and 350 eV/700 kJ (Hinkel et al ). Capsules using a polyimide ablator do not require any doping and been designed to work at 250 eV/900 kJ and 300 eV/1.3 MJ (D&rich et al 1996).…”

Section: Introductionmentioning

confidence: 99%

Capsule design for the National Ignition Facility

Dittrich¹,

Haan²,

Marinak³

et al. 1999

Laser Part. Beams

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Abstract.Several choices exist in the design and production of capsules intended to ignite and propagate fusion burn of the DT fuel when imploded by indirect drive at the National Ignition Facility. These choices include ablator material, ablator dopant concentration and distribution, capsule dimensions, and x-ray drive profile (shock timings and strengths). The choice of ablator material must also include fabrication and material characteristics, such as attainable surface finishes, permeability, strength, transparency to radio frequency and infrared radiation, thermal conductivity, and material homogeneity. Understanding the advantages and/or limitations of these choices is an ongoing effort for LLNL and LANL designers. At this time, simulations in one-two-and three-dimensions show that capsules with either a copper doped beryllium or a polyimide (C,,H,,N,O,) ablator material have both the least sensitivity to initial surface roughnesses and favorable fabrication qualities. Simulations also indicate the existence of capsule designs based on these ablator materials which ignite and burn when imploded by less than nominal laser performance (900 kJ energy, 250 TW power, producing 250 eV peak radiation temperature). We will describe and compare these reduced scale capsules, in addition to several designs which use the expected 300 eV peak x-ray drive obtained from the nominal NIF laser (1.3 MJ, 500 TW). Introduction.National Ignition Facility (NIF) (Paisner et al. 1994) capsule designs cover a range of x-ray drive temperatures, ablator materials, and total laser energies. Ablator materials studied to date include polystyrene (CH) doped with bromine (Br) or germanium (Ge), beryllium (Be) doped with copper (Cu), and polyimide (C,,H,,N,O,). Numerical simulations show that a capsule design using a CH ablator requires a dopant material such as Br or Ge to achieve optimum performance when imploded by a 300 eV peak temperature x-ray source obtained from a 1.3 MJ total energy laser. According to simulations, capsule designs using a Be ablator also require doping (e.g., with Cu) in order to achieve optimum performance. Currently, these Be ablator capsule designs span several peak x-ray drive temperatures and total laser energies: 330 eV

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Section: Introductionmentioning

confidence: 99%

Capsule design for the National Ignition Facility

Dittrich¹,

Haan²,

Marinak³

et al. 1999

Laser Part. Beams

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“…The formation of the central hot spot and the assembly of the thermonuclear fuel requires implosions velocities of 350 km/s and a symmetrically compressed capsule to a sphere with a diameter of 60 µm. While round implosions have been demonstrated by controlling the laser beam power on the hohlraum wall either by directly tuning the power of individual beams [7][8][9] or more efficiently with self-generated plasma optics gratings on the NIF [10,11], the implosion velocity and compression are directly related to the hohlraum radiation temperature and consequently to the absorbed laser energy in the hohlraum [12,13].…”

mentioning

confidence: 99%

Demonstration of Ignition Radiation Temperatures in Indirect-Drive Inertial Confinement Fusion Hohlraums

Glenzer¹,

MacGowan²,

Meezan³

et al. 2011

Phys. Rev. Lett.

105

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“…This "indirect-drive" laser geometry has been chosen for the first experiments to heat the interior of centimeter-scale cylindrical gold hohlraums (8,(12)(13)(14)(15) through laser entrance holes (LEH) on the top and bottom end of the cylinder (Fig. 1).…”

mentioning

confidence: 99%

Symmetric Inertial Confinement Fusion Implosions at Ultra-High Laser Energies

Glenzer

MacGowan

Michel

et al. 2010

Science

333

184

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Indirect-drive hohlraum experiments at the National Ignition Facility have demonstrated symmetric capsule implosions at unprecedented laser drive energies of 0.7 MJ. 192 simultaneously fired laser beams heat ignition emulate hohlraums to radiation temperatures of 3.3 million Kelvin compressing 1.8-millimeter capsules by the soft x rays produced by the hohlraum. Self-generated plasma-optics gratings on either end of the hohlraum tune the laser power distribution in the hohlraum producing symmetric x-ray drive as inferred from the shape of the capsule self-emission. These experiments indicate conditions suitable for compressing deuterium-tritium filled capsules with the goal to achieve burning fusion plasmas and energy gain in the laboratory.With completion (1) and commissioning (2) of the National Ignition Facility (NIF) the quest for producing a burning fusion plasma has begun (3, 4). The goal of these experiments is to compress matter to densities and temperatures higher than the interior of the sun (5-7) which will initiate nuclear fusion and burn of hydrogen isotopes (8-10). This technique holds promise to demonstrate a highly efficient carbon-free process that will burn milligram quantities of nuclear fuel on each laser shot for producing energy gain in the laboratory.The NIF (11) consists of 192 laser beams that have been arranged into cones of beams to irradiate a target from the top and bottom hemispheres. This "indirect-drive" laser geometry has been chosen for the first experiments to heat the interior of centimeter-scale cylindrical gold hohlraums (8,(12)(13)(14)(15) through laser entrance holes (LEH) on the top and bottom end of the cylinder (Fig. 1). Hohlraums act as radiation enclosures that convert the optical laser light into soft x-rays that are characterized by the radiation temperature T RAD . Present ignition designs operate at temperatures of 270 to 305 eV or 3.1 to 3.5 million K. The radiation field compresses a spherical fusion capsule mounted in the center of the hohlraum by x-ray ablation of the outer shell. The ablation process compresses the cryogenically prepared solid deuterium-tritium fuel layer in a spherical rocket implosion. In the final stages, the fuel reaches densities 1000-times solid and the central hot spot temperatures will approach 100 million K to initiate the nuclear burn process.We have symmetrically imploded 1.8-mm diameter fusion capsules in cryogenically fielded centimeter-scale hohlraums at 20 K. These experiments show efficient hohlraum heating to radiation temperatures of 3.3 million K. In addition, the large scale-length plasmas encountered in these experiments have allowed us to use self-generated plasma optics gratings (16) to control the radiation symmetry (17) and to achieve symmetric fusion capsule implosions.Figure 2 A shows the laser power at the frequency-tripled wavelength of 351 nm versus time for two different pulse shapes. These 11-ns and 16-ns long pulses heat 8.4-mm long, 4.6-mm diameter hohlraums with 20% helium, 80% hydrogen (atomic) mixtures and ...

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Ignition target design and robustness studies for the National Ignition Facility

Cited by 99 publications

References 19 publications

Capsule design for the National Ignition Facility

Capsule design for the National Ignition Facility

Demonstration of Ignition Radiation Temperatures in Indirect-Drive Inertial Confinement Fusion Hohlraums

Symmetric Inertial Confinement Fusion Implosions at Ultra-High Laser Energies

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