Plasma heating by a relativistic electron beam

Abstract

Reported are measurements on the interaction between a relativistic electron beam (REB) with the parameters 800 kV, 6 kA, 50–150 nsec, and a plasma with a density of ne=1.0×1019 m−3–1.0×1020 m−3. The electron temperature during and after the beam pulse is obtained by means of Thomson scattering. Also measured is the angular distribution of the beam electrons as a function of time and position. By varying the angular spread of the beam it is possible to pass from a kinetic to a quasihydrodynamic interaction. In both regimes measurements are compared with the appropriate theoretical model. Energy transfer is largest in the quasihydrodynamic regime and amounts to 2.5×103 J/m3 or 2.2×1016 eV/cm3. The electron temperature reaches values of 150 eV and appears limited by the electron heat conduction along the magnetic field.

Systematic approximations for magnetized transit-time interactions

“…In this section, we outline the analytic theory of magnetized, electrostatic transit-time interactions, extending the results of Melatos & Robinson (1993a) to accommodate non-axisymmetric wave packets. From the general expressions for the first-and second-order wave-particle energy transfers, we identify the algebraic forms of the integrals to be approximated in § §4 and 5.…”

“…The field phase (f> is that seen by the particle at t = 0. As discussed by Melatos & Robinson (1993a, b), maximizing W with respect to 0 yields the energy scattering experienced by a monoenergetic ensemble of particles, while averaging W over <p yields the mean wave disspiation by such an ensemble.…”

“…The analytical perturbation theory of transit-time interactions (Morales & Lee 1974;) has recently been extended to treat interactions in magnetic fields (Lamb, Dimonte & Morales 1984;Melatos& Robinson 1993a, 6). A drawback of the theory in this general form is its algebraic complexity, which makes practical calculations onerous -even numerically.…”

“…Transit-time dissipation is an especially important process in strongly turbulent plasmas, where it acts to arrest the nonlinear collapse of coherent Langmuir or lower-hybrid wave packets at short scales ( « 20A D ) and intense fields . Arrest of wave collapse, and the transit-time acceleration associated with it, therefore feature prominently in a wide variety of physical situations, among them relativistic electron-beam experiments (Jannsen et al 1984;), microwave-plasma and laser-plasma systems (e.g. Wong, Leung & Eggleston 1977), the earth's electron foreshock (Robinson & Newman 1991) and computer simulations of strong turbulence (Newman et al 1990, and references therein).…”

Nonlinear High Harmonics Generation in REB-Plasma System

“…It is not surprising to find up till now a long list of studies and research on beam-plasma interaction and applications, which was also reviewed by many authors, e.g. [1][2][3][4][5][6][7].…”