The response of electrons in a collisionless plasma to a fast‐rising voltage step is investigated experimentally and theoretically. At small amplitudes the step generates a wave train, the leading edge of which propagates along the column at the long‐wavelength electron plasma wave velocity. At large step amplitudes a fast burst of electrons is observed, with kinetic energy roughly proportional to the step amplitude, followed by a nonlinear electron plasma wave signal which shows solitonlike behavior.
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This assumption about the absence of higher modes cannot be resolved theoretically since we do not yet know the radial structure of the electron plasma wave peak. However, the presence of only one electron plasma wave signal (at the density at which Fig. 6, for example, was obtained) suggests that higher modes are at least strongly damped, if not altogether absent. Modemode coupling to higher modes would then provide a mechanism for the damping of the lowest mode (see Fig. 6).
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© 1971 American Institute of Physics.
1971
American Institute of Physics
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