J. Perkins

Bio: J. Perkins is an academic researcher. The author has contributed to research in topics: Ignition system & Shock (mechanics). The author has an hindex of 1, co-authored 1 publications receiving 365 citations.

Shock Ignition of Thermonuclear Fuel with High Areal Density

Abstract: A novel method by C. Zhou and R. Betti [Bull. Am. Phys. Soc. 50, 140 (2005)] to assemble and ignite thermonuclear fuel is presented. Massive cryogenic shells are first imploded by direct laser light with a low implosion velocity and on a low adiabat leading to fuel assemblies with large areal densities. The assembled fuel is ignited from a central hot spot heated by the collision of a spherically convergent ignitor shock and the return shock. The resulting fuel assembly features a hot-spot pressure greater than the surrounding dense fuel pressure. Such a nonisobaric assembly requires a lower energy threshold for ignition than the conventional isobaric one. The ignitor shock can be launched by a spike in the laser power or by particle beams. The thermonuclear gain can be significantly larger than in conventional isobaric ignition for equal driver energy.

Direct-drive inertial confinement fusion: A review

Abstract: 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.

Inertial-confinement fusion with lasers

Abstract: The quest for controlled fusion energy has been ongoing for over a half century. The demonstration of ignition and energy gain from thermonuclear fuels in the laboratory has been a major goal of fusion research for decades. Thermonuclear ignition is widely considered a milestone in the development of fusion energy, as well as a major scientific achievement with important applications in national security and basic sciences. The US is arguably the world leader in the inertial confinement approach to fusion and has invested in large facilities to pursue it, with the objective of establishing the science related to the safety and reliability of the stockpile of nuclear weapons. Although significant progress has been made in recent years, major challenges still remain in the quest for thermonuclear ignition via laser fusion. Here, we review the current state of the art in inertial confinement fusion research and describe the underlying physical principles. The quest for energy production from controlled nuclear fusion reactions has been ongoing for many decades. Here, the inertial confinement fusion approach, based on heating and compressing a fuel pellet with intense lasers, is reviewed.

Fast ignition with laser-driven proton and ion beams

Abstract: Fusion fast ignition (FI) initiated by a laser-driven particle beam promises a path to high-yield and high-gain for inertial fusion energy. FI can readily leverage the proven capability of inertial confinement fusion (ICF) drivers, such as the National Ignition Facility, to assemble DT fusion fuel at the relevant high densities. FI provides a truly alternate route to ignition, independent of the difficulties with achieving the ignition hot spot in conventional ICF. FI by laser-driven ion beams provides attractive alternatives that sidestep the present difficulties with laser-driven electron-beam FI, while leveraging the extensive recent progress in generating ion beams with high-power density on existing laser facilities. Whichever the ion species, the ignition requirements are similar: delivering a power density ≈1022 W cm−3 (∼10 kJ in ≈20 ps within a volume of linear dimension ≈20 µm), to the DT fuel compressed to ∼400 g cm−3 with areal density ∼2 g cm−2. High-current, laser-driven beams of many ion species are promising candidates to deliver such high-power densities. The reason is that high energy, high-power laser drivers can deliver high-power fluxes that can efficiently make ion beams that are born neutralized in ∼fs–ps timescales, making them immune to the charge and current limits of conventional beams. In summary, we find that there are many possible paths to success with FI based on laser-driven ion beams. Although many ion species could be used for ignition, we concentrate here on either protons or C ions, which are technologically convenient species. We review the work to date on FI design studies with those species. We also review the tremendous recent progress in discovering, characterizing and developing many ion-acceleration mechanisms relevant to FI. We also summarize key recent technological advances and methods underwriting that progress. Based on the design studies and on the increased understanding of the physics of laser-driven ion acceleration, we provide laser and ion-generation laser-target design points based on several distinct ion-acceleration mechanisms.