A Continuous, In-Chamber Target Tracking and Engagement Approach for Laser Fusion

Petzoldt, Ron; Alexander, Neil B.; Carlson, L.; Flint, Graham; Goodin, D. T.; Spalding, Jon; Tillack, M. S.

doi:10.13182/fst07-a1529

Cited by 14 publications

(11 citation statements)

References 1 publication

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“…898 The concept uses a low-intensity laser to reflect off the Au-Pd coating on the target surface. This glint reflection is then used to direct the final steering mirrors to precisely illuminate the target.…”

Section: Target Tracking/placementmentioning

confidence: 99%

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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Section: Target Tracking/placementmentioning

confidence: 99%

Direct-drive inertial confinement fusion: A review

et al. 2015

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“…This approach was successfully used for target position detection performed by Petzoldt at all. [1,2] in 2007.…”

Section: Introductionmentioning

confidence: 99%

“…There is possible to use 1D or 2D photo detectors and evaluate the target off axis displacement with numerical data processing. It was presented evaluation of target off axis position from a Poisson spot displacement measurement [1,2] and shadow figures [3] recently. Employment these kinds of detectors leads to digitizing the target off axis position data to few positions along the target main movement direction given by a detector sampling frequency.…”

Section: Introductionmentioning

confidence: 99%

Alternative fusion target tracking techniques

et al. 2011

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This paper presents a short analysis of possible techniques for fusion targets tracking in rep-rate regime. Target tracking solution is limited with necessity of high speed, high precise and long-distance measurement combined with a harsh environment of the vacuum fusion chamber. The only optical measurement seems to be usable to meet required conditions to measurement system. Few standards and less traditional methods are presented in this paper. Its possibility to meet the target goal resolution is discussed. Preparation of experimental techniques for verification of measurement conditions of suggested methods is shown too.

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“…Targets must be injected into the chamber with a placement accuracy of ± 1 mm at a standoff distance of~20 m. The required engagement accuracy of the driver beams is ± 20 mm in 3-dimensions (also at a standoff of ~20 m. ) We have developed a target tracking and engagement concept to meet these requirements and have assembled a tabletop experiment that engages an injected target onthe-fly. 1 This method differs from previous approaches 2 in that it uses continuous tracking along the target's trajectory together with a final steering correction that is made relative to the target itself. The tabletop experiment will demonstrate proof-of-principle at reduced speeds and distances and will establish the concepts' feasibility for a real power plant.…”

Section: Introductionmentioning

confidence: 99%