| Research Abstract |
Experimental results : (1) The coupling between an upper hybrid solitary wave (soliton) and an ion wave (caviton) is found experimentaly in the beam-plasma system. The ion wave appears as the triangular wave with steep negative front on the beam collector current and the soliton coincide with this front. This means that the beam electron emits the soliton when the beam collide to the steep negative front of the ion wave by the Bremsstrahlung in the decelera-tion field. In the region of high plasma density, the ion waves appear as cavitons. IF the ratio between the density depression of the caviton deltan and the normal density n satisfies inequality, deltan/n<greater than or equal> 0.5, then a strong beam-plasma discharge by high frequency starts
(2) The soliton turns up intermittently as a burst, the sustained time of which is 300ns-600ns in the low plasma density and 800ns-1mus at high plasma density. The phase of carrier in the soliton is confirmed to be continuous.
(3) In the low plasma density, the soliton forms a slender style of hyperbolic secant curve, however at high plasma density, the soliton amplitude lessens and its time width increases by the nonlinear Landau damping. The style of the soliton is not the hyperbolic secant function, in contrast to lower density case, but has many fine splits, showing that the modulation at in-stability happens to appear.
Theoretical results : (1) We succeeded theoretically in an attempt to described the emis-sion of the soliton with a completely nonlinear theory. It is found that the presence of slower responce of ions is necessary for tile emission, i.e., without the ions, the electron beam can not emit a. soliton.
(2) The deformation of wave envelope from the hyperbolic secant curve is analized as an initial value problems of the nonlinear Schrodinger equation with an nonlinear Landau damping term. We get the satisfactry results compared with the experiments.
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