Preface 1. Basic concepts 2. The Vlasov, two-fluid, and MHD models of plasma dynamics 3. Motion of a single plasma particle 4. Elementary plasma waves 5. Streaming instabilities and the Landau problem 6. Cold plasma waves in a magnetized plasma 7. Waves in inhomogeneous plasmas and wave energy relations 8. Vlasov theory of warm electrostatic waves in a magnetized plasma 9. MHD equilibria 10. Stability of static MHD equilibria 11. Magnetic helicity interpreted and Woltjer-Taylor relaxation 12. Magnetic reconnection 13. Fokker-Planck theory of collisions 14. Wave-particle nonlinearities 15. Wave-wave nonlinearities 16. Non-neutral plasmas 17. Dusty plasmas Appendix A. Intuitive method for vector calculus identities Appendix B. Vector calculus in orthogonal curvilinear coordinates Appendix C. Frequently used physical constants and formulae Bibliography References Index.

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Fundamentals of Plasma Physics

The use of intense laser light to bring about thermonuclear reactions in a plasma is of considerable current interest. We present detailed analytical and computational studies which show the feasibility of laser-driven fusion. The required laser technology and the presently anticipated practical difficulties are discussed in outline.

Laser-driven fusion

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.

Direct-drive inertial confinement fusion: A review

We consider ion heating by turbulent Alfv?n waves (AWs) and kinetic Alfv?n waves (KAWs) with wavelengths (measured perpendicular to the magnetic field) that are comparable to the ion gyroradius and frequencies ? smaller than the ion cyclotron frequency ?. We focus on plasmas in which ? 1, where ? is the ratio of plasma pressure to magnetic pressure. As in previous studies, we find that when the turbulence amplitude exceeds a certain threshold, an ion's orbit becomes chaotic. The ion then interacts stochastically with the time-varying electrostatic potential, and the ion's energy undergoes a random walk. Using phenomenological arguments, we derive an analytic expression for the rates at which different ion species are heated, which we test by simulating test particles interacting with a spectrum of randomly phased AWs and KAWs. We find that the stochastic heating rate depends sensitively on the quantity ? = ?v ?/v ?, where v ? (v ?) is the component of the ion velocity perpendicular (parallel) to the background magnetic field B 0, and ?v ? (?B ?) is the rms amplitude of the velocity (magnetic-field) fluctuations at the gyroradius scale. In the case of thermal protons, when ? ?crit, where ?crit is a constant, a proton's magnetic moment is nearly conserved and stochastic heating is extremely weak. However, when ?>?crit, the proton heating rate exceeds half the cascade power that would be present in strong balanced KAW turbulence with the same value of ?v ?, and magnetic-moment conservation is violated even when ? ?. For the random-phase waves in our test-particle simulations, ?crit = 0.19. For protons in low-? plasmas, ? ??1/2?B ?/B 0, and ? can exceed ?crit even when ?B ?/B 0 ?crit. The heating is anisotropic, increasing v 2 ? much more than v 2 ? when ? 1. (In contrast, at ? 1 Landau damping and transit-time damping of KAWs lead to strong parallel heating of protons.) At comparable temperatures, alpha particles and minor ions have larger values of ? than protons and are heated more efficiently as a result. We discuss the implications of our results for ion heating in coronal holes and the solar wind.

https://iopscience.iop.org/article/10.1088/0004-637X/720/1/503/pdf

Perpendicular ion heating by low-frequency Alfven-wave turbulence in the solar wind

The experiments on solitons in plasmas performed during the period 1970 to 1982 are reviewed. Suggestions for future experiments are presented.

https://iopscience.iop.org/article/10.1088/0032-1028/25/9/001/pdf

Soliton experiments in plasmas

Laser-induced fluorescence of ionic states is used to measure local ion densities and velocities in argon plasmas.

Plasma Ion Diagnostics Using Resonant Fluorescence

Anomalously fast ion heating has been observed in the Caltech Encore tokamak [Phys. Rev. Lett. 59, 1436 (1987)], with the use of laser-induced fluorescence. This heating was found to be independent of electron temperature, but was well correlated with the presence of large-amplitude drift-Alfven waves. Evidence is presented that suggests that the heating is stochastic and occurs when the ion displacement due to polarization drift becomes comparable to the perpendicular wavelength, i.e., when k[perpendicular] (mik[perpendicular] phi0/qB^2)~1. Stochastic heating may also be the cause of the anomalously high ion temperatures observed in reversed-field pinches.

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Observation of fast stochastic ion heating by drift waves

The simultaneous excitation of electron-plasma and ion-acoustic oscillations by means of a single electromagnetic wave at $\ensuremath{\omega}\ensuremath{\cong}{\ensuremath{\omega}}_{p}$ has been observed experimentally and analyzed theoretically, with consistent results.

Parametric Coupling Between Electron-Plasma and Ion-Acoustic Oscillations

This article reports work in progress on laser diagnostics of negative‐ion transport velocity in H−‐ion volume sources. The plasma dynamics after the laser shot is discussed in detail, and the effect of the potential perturbation on the H− velocities is evaluated. A method of evaluation of the H− transport velocity from single‐laser‐beam photodetachment experiments is proposed. To substantiate this method, two‐laser‐beam photodetachment experiments have been effected. The velocities thus determined are pressure dependent; they correspond to H− energies in the range 0.23–0.08 eV.

Photodetachment technique for measuring H− velocities in a hydrogen plasma

Anomalously fast ion heating has been observed in the Caltech Encore tokamak [Phys. Rev. Lett. 59, 1436 (1987)], with the use of laser‐induced fluorescence. This heating was found to be independent of electron temperature, but was well correlated with the presence of large‐amplitude drift‐Alfven waves. Evidence is presented that suggests that the heating is stochastic and occurs when the ion displacement due to polarization drift becomes comparable to the perpendicular wavelength, i.e., when k⊥ (mik⊥ φ0/qB2)∼1. Stochastic heating may also be the cause of the anomalously high ion temperatures observed in reversed‐field pinches.

/pdf/observation-of-fast-stochastic-ion-heating-by-drift-waves-4q0rr0ctn8.pdf

R. A. Stern

Papers

Plasma Ion Diagnostics Using Resonant Fluorescence

Observation of fast stochastic ion heating by drift waves

Parametric Coupling Between Electron-Plasma and Ion-Acoustic Oscillations

Photodetachment technique for measuring H− velocities in a hydrogen plasma

Observation of fast stochastic ion heating by drift waves