Objectives
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| In some settings, when the production rate of electrons is too high in comparison with losses, the potential on axis may drop down to negative values. Electrons in this region are no more confined and could escape the lens longitudinally. The typical column with a hollow profile will be then constitute (A-C) and ExB drift waves are observed. It is well studied (for example [1]) that such kind of annular layer lead to so called diocotron instabillity (D-I). |
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3D-PIC(Particle-in-cell) simulation results of a confined electron cloud under such conditions are shown in picture above. Evolution time (A-I) corresponds here to 6e-7s. The simulation was done on 36 processors of CSC(Computer for Scientific Computation) computer cluster and 4e+6 Macro-particles. The azimuthal modes l=1, l=2, l=3 are unstable (D-F). Afterwards mode l=4 seems stable. Literature: |