Considerations and Requirements for Providing Cryogenic Targets for Direct-Drive Inertial Fusion Implosions at the National Ignition Facility

Harding, D. R.; Wittman, Mark D.; Edgell, D. H.

doi:10.13182/fst13-a16326

Cited by 13 publications

(11 citation statements)

References 8 publications

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“…Another layering process succeeds in realizing low RMS surface roughness. In order to meet the requirement within 1 µm RMS roughness for central ignition experiments, a monocrystal solid fuel layer is formed [30,31]. Starting from a seed crystal is required to grow a monocrystal solid layer.…”

Section: Resultsmentioning

confidence: 99%

Preliminary Cryogenic Layering by the Infrared Heating Method Modified with Cone Temperature Control for the Polystyrene Shell FIREX Target

Iwano

Iwamoto

Yamanoi

et al. 2021

Plasma and Fusion Research

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The infrared (IR) heating method for a central ignition target with spherical symmetry is modified for the axisymmetric Fast Ignition Realization EXperiment (FIREX) target. The challenge is that the FIREX target pretends to be a thermally spherical shell. Our previous simulation studies (A. Iwamoto et al., Fusion Sci. Technol. 56, 427 (2009), A. Iwamoto et al., J. Phys.: Conf. Ser. 244, 032039 (2010) have shown that the combination of volumetric heating in a fuel and cone temperature control has the potential to finish a uniform fuel layer. We have developed the IR heating system, dedicated to the FIREX target, with exclusive cone temperature control. The ability of solid fuel layering was examined by using an 826 µm polystyrene (PS) shell with a gold cone of 1.2 mm in length instead of the 500 µm FIREX target for easy observation. The system could control the profile of a solid fuel layer in the PS shell target. Eventually, the solid layer with the best sphericity of 92% was formed, and the RMS roughness of the inner surface was 44 -49 µm in modes 1 to 100 and 14 -26 µm in modes 5 to 100.

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Section: Resultsmentioning

confidence: 99%

Preliminary Cryogenic Layering by the Infrared Heating Method Modified with Cone Temperature Control for the Polystyrene Shell FIREX Target

Iwano

Iwamoto

Yamanoi

et al. 2021

Plasma and Fusion Research

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“…13-10) shows good agreement. 708 In this experiment, the D 2 gas used to fill the target was contained in a 4-cm 3 reservoir, held at a higher temperature (<5 K differential) than the target to provide the pressure differential needed to force the gas into the target. Liquid was contained in the target by cooling the fill tube to create an ice plug.…”

Section: Ice-layer Characterizationmentioning

confidence: 99%

“…Further information on the fill-tube/reservoir system being developed for the NIF is found in Ref. 708.…”

Section: Ice-layer Characterizationmentioning

confidence: 99%

“…A more-recent 3-D version of the model was used to calculate the DT ice-thickness uniformity of a NIF direct-drive target attached to a fill tube and positioned inside the prototype cryogenic system 708 [ Fig. 13-1(e)].…”

Section: Ice-layer Characterizationmentioning

confidence: 99%

“…The FLUENT model was also used to evaluate the effect on the ice layer of not having the target optimally positioned in the layering sphere. 708 The following three topics remain active areas of study because they can affect the implosion performance: (1) the presence of 3 He resulting from tritium decay; (2) fractionation of the D 2 , DT, and T 2 isotopes during crystal growth (radial variation of the isotopic ratio because of the triple-point He is minimized by purifying the tritium source using a Pd permeation membrane, 329 filling the target rapidly through a fill tube, and minimizing the life span of the target. The accumulation of 3 He in the ice layer does not affect the ice roughness if the ice layer is less than one week old.…”

Section: Ice-layer Characterizationmentioning

confidence: 99%

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Direct-drive inertial confinement fusion: A review

et al. 2015

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The direct-drive, laser-based approach to inertial confinement fusion (ICF) is reviewed from its inception following the demonstration of the first laser to its implementation on the present generation of high-power lasers. The review focuses on the evolution of scientific understanding gained from target-physics experiments in many areas, identifying problems that were demonstrated and the solutions implemented. The review starts with the basic understanding of laser–plasma interactions that was obtained before the declassification of laser-induced compression in the early 1970s and continues with the compression experiments using infrared lasers in the late 1970s that produced thermonuclear neutrons. The problem of suprathermal electrons and the target preheat that they caused, associated with the infrared laser wavelength, led to lasers being built after 1980 to operate at shorter wavelengths, especially 0.35 μm—the third harmonic of the Nd:glass laser—and 0.248 μm (the KrF gas laser). The main physics areas relevant to direct drive are reviewed. The primary absorption mechanism at short wavelengths is classical inverse bremsstrahlung. Nonuniformities imprinted on the target by laser irradiation have been addressed by the development of a number of beam-smoothing techniques and imprint-mitigation strategies. The effects of hydrodynamic instabilities are mitigated by a combination of imprint reduction and target designs that minimize the instability growth rates. Several coronal plasma physics processes are reviewed. The two-plasmon–decay instability, stimulated Brillouin scattering (together with cross-beam energy transfer), and (possibly) stimulated Raman scattering are identified as potential concerns, placing constraints on the laser intensities used in target designs, while other processes (self-focusing and filamentation, the parametric decay instability, and magnetic fields), once considered important, are now of lesser concern for mainline direct-drive target concepts. Filamentation is largely suppressed by beam smoothing. Thermal transport modeling, important to the interpretation of experiments and to target design, has been found to be nonlocal in nature. Advances in shock timing and equation-of-state measurements relevant to direct-drive ICF are reported. Room-temperature implosions have provided an increased understanding of the importance of stability and uniformity. The evolution of cryogenic implosion capabilities, leading to an extensive series carried out on the 60-beam OMEGA laser [Boehly et al., Opt. Commun. 133, 495 (1997)], is reviewed together with major advances in cryogenic target formation. A polar-drive concept has been developed that will enable direct-drive–ignition experiments to be performed on the National Ignition Facility [Haynam et al., Appl. Opt. 46(16), 3276 (2007)]. The advantages offered by the alternative approaches of fast ignition and shock ignition and the issues associated with these concepts are described. The lessons learned from target-physics and implosion experiments are taken into account in ignition and high-gain target designs for laser wavelengths of 1/3 μm and 1/4 μm. Substantial advances in direct-drive inertial fusion reactor concepts are reviewed. Overall, the progress in scientific understanding over the past five decades has been enormous, to the point that inertial fusion energy using direct drive shows significant promise as a future environmentally attractive energy source.

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Mechanical Design and Analysis of an Indirect-drive Cryogenic Target

Hong

Lei

et al. 2016

J Fusion Energ

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Considerations and Requirements for Providing Cryogenic Targets for Direct-Drive Inertial Fusion Implosions at the National Ignition Facility

Cited by 13 publications

References 8 publications

Preliminary Cryogenic Layering by the Infrared Heating Method Modified with Cone Temperature Control for the Polystyrene Shell FIREX Target

Preliminary Cryogenic Layering by the Infrared Heating Method Modified with Cone Temperature Control for the Polystyrene Shell FIREX Target

Direct-drive inertial confinement fusion: A review

Mechanical Design and Analysis of an Indirect-drive Cryogenic Target

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