A comparison of three-dimensional multimode hydrodynamic instability growth on various National Ignition Facility capsule designs with <scp>HYDRA</scp> simulations

Marinak, M. M.; Haan, S. W.; Dittrich, Thomas; Tipton, Robert; Zimmerman, G. B.

doi:10.1063/1.872643

Cited by 126 publications

(64 citation statements)

References 31 publications

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“…The energy distribution for the intrinsic prepulse, the auxiliary prepulse and the main pulse were measured by sampling beam leakage through the last turning mirror prior to the final focusing optic, at a plane equivalent to the focal plane on target [13]. Best focus for both the prepulse and the main pulse was set at the inside surface of the cone tip.The system was modeled in two parts: (i) The radiativehydro code HYDRA [14] was used to calculate the distribution of the preformed plasma created by laser ablation from the inside wall of the cone due to the prepulse; (ii) the plasma simulation code PSC [15] was used to perform a massively parallel particle in cell (PIC) simulation of the ultraintense short pulse laser interaction with the pre- PRL 104, 055002 (2010) …”

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confidence: 99%

“…The system was modeled in two parts: (i) The radiativehydro code HYDRA [14] was used to calculate the distribution of the preformed plasma created by laser ablation from the inside wall of the cone due to the prepulse; (ii) the plasma simulation code PSC [15] was used to perform a massively parallel particle in cell (PIC) simulation of the ultraintense short pulse laser interaction with the pre-…”

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confidence: 99%

“…The density of the cone wall was clamped at 100Â critical (n c ) to avoid numerical heating. The initial conditions for the PIC simulation were imported from a 2D hydrodynamic simulation performed using HYDRA [14] to model the actual target geometry and the experimentally measured prepulse (both intrinsic and external). The near field intensity distribution of the Titan laser was reconstructed from the measured high power focal spot, resulting in an aberrated spot consistent with experiment.…”

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Limitation on Prepulse Level for Cone-Guided Fast-Ignition Inertial Confinement Fusion

MacPhee¹,

Divol²,

Kemp³

et al. 2010

Phys. Rev. Lett.

108

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The viability of fast-ignition (FI) inertial confinement fusion hinges on the efficient transfer of laser energy to the compressed fuel via multi-MeV electrons. Preformed plasma due to the laser prepulse strongly influences ultraintense laser plasma interactions and hot electron generation in the hollow cone of an FI target. We induced a prepulse and consequent preplasma in copper cone targets and measured the energy deposition zone of the main pulse by imaging the emitted K radiation. Simulation of the radiation hydrodynamics of the preplasma and particle in cell modeling of the main pulse interaction agree well with the measured deposition zones and provide an insight into the energy deposition mechanism and electron distribution. It was demonstrated that a under these conditions a 100 mJ prepulse eliminates the forward going component of $2-4 MeV electrons. Cone-guided fast-ignition inertial confinement fusion (FI) depends on the efficient transfer of laser energy to a forward directed beam of $2 MeV electrons at the tip of a hollow cone embedded in the side of an inertialconfinement fusion fuel capsule [1]. This scheme is particularly susceptible to laser prepulse [2,3] as the cone wall confines the expanding preformed plasma [4,5] increasing both density scale lengths and laser beam filamentation [6].The igniter laser pulse requirements for fast ignition depend on the conversion efficiency from laser energy to hot electrons [7], the electron energy spectrum [8], the electron transport efficiency to the ignition hot spot [9,10], and the electron energy deposition efficiency in the hot spot [10]. The required laser energy has been estimated at approximately 100 kJ in a 20 ps pulse [1,11]. Since the ignition hot spot diameter is $40 m, the cone tip must be similar in diameter and the laser intensity $4 Â 10 20 W=cm 2 . Existing petawatt class laser systems deliver up to 1 kJ with typical energy contrast $1 Â 10 À5 and with nonlinear devices this ratio can be improved by a further order of magnitude [12]. Contrast due to amplified superfluorescence and spontaneous emission is independent of the final laser energy; hence, for an ignition pulse of 100 kJ the prepulse energy on target could range from 100 mJ to 1 J. Recent work by Baton et al. [5] has shown that some amount of prepulse can strongly affect coupling to cones; however, a detailed understanding of this limit has not been reported.In this Letter we report recent studies of laser interactions with hollow cone targets comparing simulations and experiments in conditions approaching full fast ignition (FI) using prepulse up to 100 mJ with main pulse irradiance $10 20 W cm À2 for picosecond durations. These parameters were accessible using the Titan laser at LLNL, which delivers ð150 AE 10Þ J in ð0:7 þ = À 0:2Þ ps at 1 m with $10% of the energy deposited above an intensity of $10 20 W cm À2 at best focus, as described in [13].We compare coupling for two well-characterized prepulse conditions: (1) an intrinsic Titan laser prepulse with ð7:5 AE 3Þ mJ in 1.7 n...

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Limitation on Prepulse Level for Cone-Guided Fast-Ignition Inertial Confinement Fusion

MacPhee¹,

Divol²,

Kemp³

et al. 2010

Phys. Rev. Lett.

108

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“…Polyimide, with its O and N content, is best left undoped at 300 eV, and is too opaque to make a good ablator at 250 eV. These three ablators-polyimide, CH(Ge), and Be(Cu), all uniformly doped or undoped-have been the mainline NIF targets, and considerable work has been done investigating their features [7,8,9]. Concurrently, some work was done with radially graded dopants.…”

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confidence: 99%

Increasing robustness of indirect drive capsule designs against short wavelength hydrodynamic instabilities

et al. 2005

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Simulations indicate dramatically reduced growth of short wavelength hydrodynamic instabilities, resulting from two changes in the designs. First, better optimization results from systematic mapping of the ignition target performance over the parameter space of ablator and fuel thickness combinations, using techniques developed by one of us (Herrmann). After the space is mapped with one-dimensional simulations, exploration of it with two-dimensional simulations quantifies the dependence of instability growth on target dimensions. Low modes and high modes grow differently for different designs, allowing a trade-off of the two regimes of growth. Significant improvement in high-mode stability can be achieved, relative to previous designs, with only insignificant increase in low-mode growth. This procedure produces capsule designs that, in simulations, tolerate several times the surface roughness that could be tolerated by capsules optimized by older more heuristic techniques. Another significant reduction in instability growth, by another factor of several, is achieved with ablators with radially varying dopant. In this type of capsule the mid-Z dopant, which is needed in the ablator to minimize xray preheat at the ablator-ice interface, is optimally positioned within the ablator. A fabrication scenario for graded dopants already exists, using sputter coating to fabricate the ablator shell. We describe the systematics of these advances in capsule design, discuss the basis behind their improved performance, and summarize how this is affecting our plans for NIF ignition.

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“…However most of the current design emphasis in the ICF field is on minimizing laser and capsule size. [6][7][8] In such optically thin systems, radiation is predominantly a volume loss term with negligible reabsorption and negligible Compton scattering. Advanced designs, such as the fast ignition concept, [9][10][11] are intended to burn much more fuel mass, but still operate mostly as transparent to the emitted x rays.…”

Section: Introductionmentioning

confidence: 99%

Photon coupling theory for plasmas with strong Compton scattering: Four temperature theory

et al. 2009

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ARTICLES YOU MAY BE INTERESTED INStudy of the ion kinetic effects in ICF run-away burn using a quasi-1D hybrid model Physics of Plasmas 24, 022704 (2017) When an equimolar mixture of deuterium ͑D͒ and tritium ͑T͒ at high density undergoes fusion burn, the system becomes extremely nonequilibrium. The ion temperature rises much higher than the electron temperature which, in turn, is much higher than the radiation temperature. Accurately simulating this nonequilibrium burn process has previously required a multigroup representation of the radiation field. Although simulating this D-T burn with a simple three temperature model ͑3T͒ also results in significant departures from thermal equilibrium, the ion and electron temperature histories from the 3T simulations are much lower than from the multigroup simulations. In this paper, a theory that overcomes the deficiencies of the 3T model in simulating burn of high density D-T is developed. The primary deficiency of the 3T model for this physical system is with the treatment of the Compton scattering energy exchange. The theory here developed culminates in a four temperature model ͑4T͒ which describes the radiation field with two temperatures. These are T R , which is the standard radiation temperature of the 3T model ͑proportional to the fourth root of the radiation energy density͒, and T p , which is the true thermodynamic temperature of the photon distribution. This 4T theory gives excellent agreement with the multigroup model for the nonequilibrium burn of D-T. Further, the 4T model transitions smoothly to the 3T model when this is appropriate. Thus the kinetic theory derivation of the 4T model also provides a solid theoretical foundation for the 3T model. Extensions of the theory to inhomogeneous systems are under development to allow treatment of geometries where the computational efficiency of the 4T approach can convey a sizable advantage. There appear to be at least two important applications where the model can be applied. One is for inertial confinement fusion capsules that are optically thick and utilize volume ignition. The second application involves astrophysical accretion disks in the high temperature regime that also exhibit matter heating radiation, albeit without a fusion energy source. A reduced complexity radiation model with the associated reduced computer resource requirements has the potential to facilitate high resolution two dimensional and three dimensional simulations of these astrophysical objects.

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A comparison of three-dimensional multimode hydrodynamic instability growth on various National Ignition Facility capsule designs with HYDRA simulations

Cited by 126 publications

References 31 publications

Limitation on Prepulse Level for Cone-Guided Fast-Ignition Inertial Confinement Fusion

Limitation on Prepulse Level for Cone-Guided Fast-Ignition Inertial Confinement Fusion

Increasing robustness of indirect drive capsule designs against short wavelength hydrodynamic instabilities

Photon coupling theory for plasmas with strong Compton scattering: Four temperature theory

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