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Plasma Science, IEEE Transactions on

Issue 2 • Date April 1987

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  • Table of contents

    Publication Year: 1987 , Page(s): c1
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  • IEEE Transactions on Plasma Science

    Publication Year: 1987 , Page(s): c2
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  • Guest Editorial Introduction to the Special Issue on Plasma-Based High-Energy Accelerators

    Publication Year: 1987 , Page(s): 85 - 87
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  • On Beat Wave Excitation of Relativistic Plasma Waves

    Publication Year: 1987 , Page(s): 88 - 106
    Cited by:  Papers (4)
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    The beat wave excitation process is examined analytically in the Eulerian fluid description. The effects of plasma drifts, harmonics, pump rise time, frequency mismatch, phenomenological damping, plasma inhomogeneities, and two dimensions are discussed. The consistency between the Eulerian and Lagrangian fluid descriptions is verified. View full abstract»

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  • Electrostatic Mode Coupling of Beat-Excited Electron Plasma Waves

    Publication Year: 1987 , Page(s): 107 - 130
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    The process of beat excitation of electron plasma waves in a plasma containing a density ripple is studied theoretically, experimentally, and computationally. A simple theoretical model has been developed which, for modest experimental parameters, predicts a new beat wave saturation mechanism. This mechanism involves the excitation of a spectrum of secondary electrostatic modes which divert pump energy from the beat wave and can lead to saturation of the beat wave at an amplitude well below that expected for relativistic detuning. Experiments designed to study the coupled mode spectrum were performed. The measured properties of the electrostatic spectrum are in reasonable agreement with the theory. To bridge the gap between the idealized model and the experiment, computer simulations were performed for a variety of parameters. The results of the simulations are in excellent agreement with the theory at early times prior to the onset of purely kinetic effects. For later times the simulations exhibit qualitative behavior which is consistent with the experimental measurements. Under certain conditions the model predicts the thermal quenching of the mode coupling saturation mechanism. These predictions are also verified in the simulations. View full abstract»

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  • Temporal Energy Cascading in the Beat Wave Accelerator

    Publication Year: 1987 , Page(s): 131 - 133
    Cited by:  Papers (1)
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    A preliminary analytic study of the temporal evolution of the beat wave accelerator (BWA) has been conducted. It was found that while energy cascading is crucial to the interpretation of current simulations, it will be less important in an actual device where the existing simple fluid model will be adequate. View full abstract»

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  • Beat Wave Generation of Plasma Waves for Particle Acceleration

    Publication Year: 1987 , Page(s): 134 - 144
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    The space-time evolution of beat wave generation is studied analytically and numerically. Electromagnetic cascading, collisional damping and relativistic frequency shift of the beat plasmon are taken into account in the model. In particular, detuning and dispersion effects are investigated. The achievable plasmon amplitude depends strongly on the collisional damping. At low electron temperatures, the induced beat wave follows the laser pulse and decays rapidly behind it. At high electron temperatures, amplitude modulation appears and an intense slowly decaying plasmon wake can be excited. The wake formation is controllable by varying the pulse length or by detuning the driver slightly off resonance. The amount of electromagnetic cascading is proportional to the plasmon amplitude and the propagation distance of the pulse. The EM spectra offer excellent diagnostics for beat wave experiments, because plasmon amplitude variations are directly reflected in them. View full abstract»

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  • Relativistic Self-Focusing of Short-Pulse Radiation Beams in Plasmas

    Publication Year: 1987 , Page(s): 145 - 153
    Cited by:  Papers (15)
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    An envelope equation is derived which describes the radial evolution of a radiation beam propagating through a plasma. The radiation envelope equation contains a defocusing term due to diffraction spreading and a focusing term due to relativistic oscillations of the plasma electrons. The case of a constant density background plasma is analyzed in detail and an expression for a critical laser power is derived. For powers exceeding the critical power, the radiation envelope oscillates and does not diffract. Under certain conditions the radiation beam propagates through the plasma with a constant radius envelope. View full abstract»

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  • Laser Self-Trapping for the Plasma Fiber Accelerator

    Publication Year: 1987 , Page(s): 154 - 160
    Cited by:  Papers (6)
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    A short-pulsed intense laser is injected into an underdense plasma to sustain a self-trapped photon channel. With either high-enough intensity or strong-enough focusing the optical beam causes total electron evacuation on the beam axis. Under appropriate conditions this laser and plasma fiber system can provide a slow wave structure of the electromagnetic wave that is suitable for high-energy acceleration. View full abstract»

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  • Generation of Uniform Plasmas for Beat Wave Experiments

    Publication Year: 1987 , Page(s): 161 - 166
    Cited by:  Papers (3)
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    The laser plasma "beat wave" mechanism for the generation of ultrahigh electric fields requires plasmas of several meters length with density uniformity of about 1 percent. Multiphoton ionization of molecular hydrogen gas at a pressure of a few torr provides a scalable mechanism for generating these plasmas using the same laser beams that drive the beat wave. We describe measurements of electron density, temperature, and uniformity of plasmas generated by a frequency doubled Neodymium glass laser, at an irradiance of about 1014 W · cm-2. The plasma density corresponds to 100-percent ionization and is measured to be uniform to within the measurement errors over a length of 8 mm. View full abstract»

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  • High-Intensity CO2 Laser Breakdown of Low-Pressure Gas

    Publication Year: 1987 , Page(s): 167 - 172
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    We have performed CO2 interferometry measurements to characterize the high-intensity (1 ¿ 1.0 × 1014 W/cm2) CO2 laser breakdown in low-pressure (0.4 torr < P < 2.0 torr) dry air and demonstrate that this plasma can be used for beat wave accelerator studies. The plasma has a diameter and axial length of 0.2 mm and 2.0 mm, respectively, slightly greater than the focal diameter and depth of focus of the focusing optics. Peak electron density corresponds to partial ionization ( = 3, ne = 1.0 × 1017 cm-3) at low pressure (P = 0.4-0.5 torr) increasing to full ionization (Z = 7.2) at P > 1.0 torr. A theoretical model of laser breakdown provides insight into the time evolution of the electron density. View full abstract»

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  • Enhanced Beat Wave Saturation Amplitude in an Ionizing Plasma

    Publication Year: 1987 , Page(s): 173 - 178
    Cited by:  Papers (2)
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    The excitation of a plasma wave by two laser beams, whose frequency difference is near the plasma frequency, is studied in a plasma with a density that is slowly increasing with time due to ongoing ionization as appropriate for experiments done in laser breakdown plasmas. Numerical integration of the relativistic equation for the evolution of the wave amplitude reveals that for a rate of increase of the plasma density of approximately 1017 cm-3/ns at a laser intensity I = 1014 W/cm2, the wave amplitude can rise considerably above the relativistic saturation limit of Rosenbluth and Liu which was obtained for a plasma of constant density. This increase in plasma density compensates the reduction in plasma frequency caused by the relativistic electron mass increase when the wave amplitude is large. The frequency and phase excursions of the plasma wave are reduced for an optimum time increasing density. We find that moderate damping can stabilize both the amplitude and the phase of the plasma wave with respect to the pump. View full abstract»

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  • A Microwave-Driven Beat Wave Accelerator for Scaled Experments

    Publication Year: 1987 , Page(s): 179 - 185
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    It is shown that large-amplitude (~ 104 V/cm) plasma waves can be resonantly excited by beating microwave pumps in an open resonator filled with plasma of subcritical density. The advantages and the possibilities of scaled experiments on beat wave accelerator concepts are discussed, in particular the plasma wave growth and saturation and the role of competing instabilities. View full abstract»

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  • Nonlinear Plasma Dynanics in the Plasma Wakefield Accelerator

    Publication Year: 1987 , Page(s): 186 - 191
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    Excitation of nonlinear plasma oscillations by an ultrarelativistic electron beam is considered in this paper. It is shown, by analytical solutions of the fully relativistic nonlinear fluid equations in one dimension, that under certain conditions on the relative densities of the electron beam and the plasma, extremely large longitudinal electric fields can be generated in the wake of the beam. This scheme can be considered as a nonlinear regime of the plasma wakefield accelerator (PWFA), and is seen to have the advantage that the transformer ratio, the ratio of the maximum amplitude of the accelerating field behind the driving beam over the maximum amplitude of the decelerating field inside of the beam, can be made arbitrarily large, dependent only on the length of the driving beam. The effects of beam loading on the efficiency of this scheme are considered, and are shown to be equivalent to those predicted in the linear regime. View full abstract»

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  • Stability of the Driving Bunch in the Plasma Wakefield Accelerator

    Publication Year: 1987 , Page(s): 192 - 198
    Cited by:  Papers (6)
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    We investigate the stability of the driving electron or positron beam in the plasma wakefield accelerator (PWFA). Although the beam is subject to self-focusing, filamentation, and two-stream instability, we find that all of these can be stabilized by introducing thermal energy and an axial magnetic field. View full abstract»

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  • Simulation of the Wisconsin-Argonne Plasma Wakefield Experiment

    Publication Year: 1987 , Page(s): 199 - 202
    Cited by:  Papers (3)
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    The plasma wakefield accelerator (PWFA) is an advanced accelerator concept that uses the large electric fields that can be generated in a plasma to accelerate charged particles. We present the results of a self-consistent two-dimensional simulation of the first experiment designed to test this concept. Linear theory predicts for this experiment an accelerating gradient of approximately 95 MV/m. However, the simulations indicate that a much larger accelerating field is achieved in the plasma. This enhancement is due to strong beam pinching, which is not treated self-consistently by a linear theory. Wave steepening due to a nonlinear modulation of the background plasma is also observed. This steepening results in a phase shift that degrades the acceleration. View full abstract»

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  • Ion Plasma Wave Wakefield Accelerators

    Publication Year: 1987 , Page(s): 203 - 209
    Cited by:  Papers (3)
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    The possibility of using space-charge waves on an ion beam or column as a wakefield accelerator is discussed. The primary advantages of using ion plasma waves over electron plasma waves are that the kinetic energy and fall-time requirements on the driving beam are reduced. One disadvantage in using a lower plasma frequency is that a larger current is required to achieve the same accelerating gradient. The basic aspects of wakefield accelerators are reviewed and this concept is analyzed in this context. Particle-in-cell simulations show that wakefields utilizing ion waves, although more complicated than plasma wakefields, can produce acceleration. View full abstract»

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  • Beam Loading in Plasma Waves

    Publication Year: 1987 , Page(s): 210 - 217
    Cited by:  Papers (5)
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    Certain key accelerator issues relevant to plasma-based accelerators are studied in this article. Analytic results for important quantities of interest, such as maximum beam current, efficiency, and energy spread will be given. These results will then be compared with one-and two-dimensional particle-in-cell (PIC) computer simulations. Special emphasis will be placed on those schemes that offer not only high accelerating gradients, but also high efficiency and small energy spread. View full abstract»

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  • Plasma Focusing for High-Energy Beams

    Publication Year: 1987 , Page(s): 218 - 225
    Cited by:  Papers (6)
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    We analyze the self-focusing effect of a relativistic electron or positron beam traversing through a thin slab of plasma in a linearized fluid theory, and show that the effect is very strong. The idea of employing this effect for a plasma lens suggested by Chen is then reviewed. The self-focusing force can be made uniform over the length of the beam by injecting an appropriate precursor. Computer simulations on both thin and thick plasma lenses are presented, which show reasonable agreement with theoretical predictions. View full abstract»

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  • A Z-Pinch Plasma Lens for Focusing High-Energy Particles in an Accelerator

    Publication Year: 1987 , Page(s): 226 - 237
    Cited by:  Papers (11)
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    The high azimuthal magnetic field of a current-carrying plasma column (z-pinch) can be used to collect and focus high-energy charged particles in accelerators. The beam optics and the apparent advantages of such a linear lens compared with conventional focusing devices, such as magnets and magnetic horns, are described. When a plasma lens shall be operated in routine accelerator runs, the physics of the plasma dynamics must be largely understood and the technology has to be mastered. The results of plasma dynamics measurements and of long-term behavior tests with a plasma lens for antiproton collection are reported. The problems of the plasma dynamics control and of the plasma-wall interaction are discussed in view of the envisaged performance for antiproton collection. View full abstract»

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  • Acceleration of Electron-Positron Plasmas to High Energies

    Publication Year: 1987 , Page(s): 238 - 242
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    It is suggested that electron-positron (e+ e-) plasma can be accelerated using the concept of cyclotron autoresonance between the particles and a linearly polarized laser radiation propagating along an axial magnetic field (Bz). This scheme can also be applied for other plasmas with oppositely charged particles of equal ¿q¿/m (e.g., positive and negative ions). An e+ e- plasma can be accelerated to about 2 GeV in the first meter along a 100-kG guide magnetic field by using an Nd: glass laser (¿0 = 1 ¿m) with intensity I0 = 1018 W/cm2. The acceleration scales asymptotically as (Bz, I0 ¿0 Z2)1/3, where z is the axial distance. View full abstract»

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  • High-Energy Electron Production by Vp × B Acceleration in Microwave-Plasma Interaction Experiments

    Publication Year: 1987 , Page(s): 243 - 250
    Cited by:  Papers (4)
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    Detailed experimental observations on the microwave plasma interaction in a nonuniform plasma with weak magnetic field (¿/¿ ¿ 10-2) have revealed that high-energy electrons are produced by a process of the VP × B acceleration, where ¿ and ¿ are, respectively, electron cyclotron and microwave frequencies. The maximum energy of hot electrons increases almost linearly to about 1 keV with the RF power up to 8 kW. Hot electrons are produced from typically two regions; one in the underdense region (several centimeters down the critical layer for the resonance absorption) and the other in the resonance absorption area. The theoretical predictions have interpreted the experimental results in reasonable agreement. View full abstract»

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  • A TB-Mode Accelerator

    Publication Year: 1987 , Page(s): 251 - 255
    Cited by:  Papers (1)
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    An accelerator is proposed in which a TE-mode wave is used to drive charged particles in contrast to the usual linear accelerators in which longitudinal electric fields or TM-mode waves are supposed to be utilized. The principle of the acceleration is based on the Vp × B acceleration of a dynamo force acceleration. That is, a charged particle trapped in a transverse wave feels a constant electric field (Faraday induction field) and subsequently is accelerated when an appropriate magnetic field is externally applied in the direction perpendicular to the wave propagation. A pair of dielectric plates is used to produce a slow TE mode. Discussions will be given on what the conditions of the particle trapping are and how to stabilize the particle orbit. View full abstract»

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  • Announcing the Second Special Issue of the IEEE Transactions on Plasma Science on High-Power Microwave Generation

    Publication Year: 1987 , Page(s): 256
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  • Information for authors

    Publication Year: 1987 , Page(s): 256a
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IEEE Transactions on Plasma Sciences focuses on plasma science and engineering, including: magnetofluid dynamics and thermionics; plasma dynamics; gaseous electronics and arc technology.

 

 

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