High-energy electron acceleration by ponderomotive forces in tenuous plasmas

Boreham, B. W.; Luther‐Davies, Barry

doi:10.1063/1.326250

Cited by 60 publications

(19 citation statements)

References 14 publications

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“…Similar measurements were performed by Yergeau, Chin & Lavigne (1987), Xiong et al (1988) (a slight error in the intensity calibration there has been corrected in the present paper), Corkum, Burnett & Brunei (1988), Tuk et al (1985), and Augst et al (1989). The Keldysh (1965) parameter-similar to the threshold of the laser intensity for the correspondence principle of electromagnetic interaction separating classical and quantum-mechanical interaction ) -is less or much less than unity, while the experiments of Boreham & Hora (1979) and Boreham & Luther-Davies (1979) had a large parameter.…”

Section: Introductionmentioning

confidence: 62%

“…The present work shows that the initial electron energy might be zero because with such an assumption, one can fit the electron spectra very well. The energy of electrons emitted during ionization was observed by Boreham & Hora (1979) and Boreham & Luther-Davies (1979) with 1.06-^m, 25-ns pulses and by Corkum, Burnett & Brunei (1988) with 2-ps CO 2 laser pulses of both linear and circular polariza-tions. This indirectly indicates that the most probable initial electron energy is zero.…”

Section: Introductionmentioning

confidence: 81%

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Tunnel ionization of K and Xe atoms by an intense CO₂ laser

Xiong

Chin

1992

Laser Part. Beams

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Section: Introductionmentioning

confidence: 62%

Section: Introductionmentioning

confidence: 81%

Tunnel ionization of K and Xe atoms by an intense CO₂ laser

Xiong

Chin

1992

Laser Part. Beams

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“…A direct proof of this is the linear dependence of the fast ion energies on the charge number (which is not explainable by thermokinetics or "hot" electrons), these ions being generated in most cases after ponderomotive self-focusing (Hora 1969b) and the generation of the caviton which was discovered numerically on the basis of the preceding theory (Hora 1969b) by Shearer et al (1970). This caviton generation in numerous experiments was clear evidence of the nonlinear force [see chapter 10 of Hora (1991)], although a direct action has been demonstrated by other experiments (Boreham & Hora 1979;Boreham & Luther-Davies 1979;Baldwin & Boreham 1981).…”

Section: Introductionmentioning

confidence: 87%

Beam smoothing and temporal effects:Optimized preparation of laser beams for direct-drive inertial confinement fusion

et al. 1997

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Direct-drive laser fusion received a number of setbacks from the experimental observation in the 1960s and 1970s of very complex interactions in laser plasma experiments caused by a number of nonlinear and anomalous phenomena. Although smoothing methods were introduced intuitively or empirically-succeeding in reducing these difficulties -it was not until a few years ago that the 20-ps stochastic pulsation mechanism was discovered. We assume here that this 20-ps stochastic pulsation may be the major obstacle to achieving direct-drive fusion, even though it is now generally assumed that the major challenge to the achievement of direct-drive fusion is the Rayleigh-Taylor instability. While we do not discount the importance of the Rayleigh-Taylor mechanisms, we concentrate here on the analysis of the pulsation process. A method of analysis was developed, using time-dependent real-time computations employing a genuine two-fluid model, which includes the interior electric fields and the very large amplitude longitudinal plasma oscillations that are driven by the laser field. These mechanisms, which were first suggested in 1974, reveal themselves now as self-generated von-Laue gratings, preventing the propagation of laser radiation through the outermost plasma corona and preventing energy deposition by temporal interruption caused by thermal relaxation and the subsequent reestablishment of these gratings, and so on. The abolition of this pulsation by broad-band laser irradiation or other smoothing methods is now well understood. A synopsis of these developments is presented here, consistent with Rubbia's proposition of using the MJ drivers for laser fusion, the technology for which is now available.

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“…One has to realiZe that this result was enforced from our studies of the radial emission of electrons in vacuum (or very low density plasma with a Debye length larger than the diameter of the laser beam) [14] where the electrons are accelerated by the nonlinear force to 100 eVor 1 keY energy at neodymium glass laser intensities of 1015 0r 1016W/cm2respectively (experiments by Boreham and Luther-Davies [14] [294]). This was very easily understood from the ponderomotive part of the nonlinear force from the radial action of the gradient of the decaying square of the electric field where then according to Eq.…”

Section: Exact Gaussian Beam Cluster Injection Laser Amplifier and mentioning

confidence: 99%

“…The laser beams had a focal intensity of about 10 15 W/cm 2 . From this time delay it was possible for the first time [294] to measure the tunnel-type ionization process [295] according to the Keldysh theory [296] where the conditions of avalange ionization or the multiphoton ionization [297] are not given. Later, nearly no difference was found for other directions.…”

Section: Tenuous Plasmas Exact Beams and Free Electron Lasersmentioning

confidence: 99%

Plasmas at High Temperature and Density

Hora¹

1991

Lecture Notes in Physics Monographs

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Preface"New physics" is an appealing new keyword, not yet devalued by the ravages of inflation. But what has this to do with such an ugly field as plasma physics, steeped in classical physics, mostly outworn, with all its unsolved and ambiguous technological problems and its messy and open ended numerical studies?"New physics" is concerned with quarks, Higgs particles, grand unified theory, superstrings, gravitational waves, and the profound basics of cosmology and black holes. It is the field of astonishing quantum effects, demonstrated by the von Klitzing effect and hightemperature superconductors. But what can plasma physicists offer, after so many years of expensive and frustrating research to solve the problem of fusion energy?One may suggest that the fascinating research of chaos with applications to plasma, or the achievements of statistical mechanics applied to plasmas, has something to offer and should be the subject of attention. However, this is not the aim of this book.Complementing the traditional aim of physics, which is to interpret the phenomena of nature by generalizing laws such that exact predictions about new properties and effects can be drawn, this book demonstrates how new physics has been derived over the last 30 years from the state of matter which exists at high temperatures (plasma). The advent of the laser, with its very high energy densities and its concentration to extremely small volumes and to very short time periods, opened up a whole new regime for the interaction of materials and high-density plasmas, which enforced the appearance of the "rather new physics".Here are a few examples:• Who would have expected that optical waves in vacuum have a longitudinal component? Thomas Young discovered in 1801 the pure transversality of optical radiation. This was not understandable at that time, when it was known that mechanical waves never exist without longitudinal components. Maxwell's equation then only revealed solutions of the purely transverse plane waves in electromagnetism. Against all this traditional knowledge, the recent findings about the dynamics of electrons driven by laser beams by nonlinear forces led to thẽ xact derivation of longitudinal optical wave components.• The same nonlinear force interaction, in view of momentum transfer in experiments, led to the clarification of the angular momentum ofoptical beams and brought about the first substantiation of the photon spin by a macroscopic property.• The conditions of very high laser intensities led to nonlinear and relativistic generalization of the optical response (dielectrics and absorption) with a prediction of relativistic self-focusing to understand how GeV ions are produced by laser irradiation of solid targets.• The quantum generalization of Coulomb collisions in plasmas at high temperatures explains the anomalous resistivity, in agreement with observations where links are given between the simply derived Coulomb collision frequency and quantum electrodynamics, including stimulated emission. IX that after the first l...

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High-energy electron acceleration by ponderomotive forces in tenuous plasmas

Cited by 60 publications

References 14 publications

Tunnel ionization of K and Xe atoms by an intense CO₂ laser

Tunnel ionization of K and Xe atoms by an intense CO₂ laser

Beam smoothing and temporal effects:Optimized preparation of laser beams for direct-drive inertial confinement fusion

Plasmas at High Temperature and Density

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High-energy electron acceleration by ponderomotive forces in tenuous plasmas

Cited by 60 publications

References 14 publications

Tunnel ionization of K and Xe atoms by an intense CO2 laser

Tunnel ionization of K and Xe atoms by an intense CO2 laser

Beam smoothing and temporal effects:Optimized preparation of laser beams for direct-drive inertial confinement fusion

Plasmas at High Temperature and Density

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Product

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Tunnel ionization of K and Xe atoms by an intense CO₂ laser

Tunnel ionization of K and Xe atoms by an intense CO₂ laser