Electrostatic Oscillations Observed in Non-Neutral Electron Plasmas Confined in a Magnetic Field Gradient

Abstract

Non-neutral electron plasmas were confined in an axisymmetric magnetic mirror field of the mirror ratio R ∼ 3. Axial plasma oscillations (Trivelpiece-Gould modes), diocotron oscillations with the azimuthal mode number m = 2, and solitary waves were investigated experimentally. It was observed that the velocities of an electron soliton and an electron hole decreased at high field side in a magnetic mirror confinement.

Nonneutral Electron Plasmas Confined in a Compact Magnetic Mirror Trap

“…The error becomes larger at the higher field, because the pulse shape becomes broader at the higher field. In previous experiments, 21) it was found that the solitary waves excited in a magnetic field gradient have a higher velocity at the lower field. Although a similar behavior is observed in the current experiment, the details should be checked carefully for the current device.…”

“…The azimuthally segmented electrodes can be used to apply rotating electric fields and to detect azimuthal plasma oscillations. As mentioned in previous papers, [19][20][21] the multiring electrode configuration is quite flexible to apply various electric fields. Two examples of calculated electric potentials along the axis of symmetry are shown in Fig.…”

“…Recently, the basic properties of nonneutral electron plasmas in a magnetic field gradient, i.e., the confinement time, electrostatic oscillations including solitary waves, and the density and potential profiles have been investigated experimentally. [19][20][21] In these experiments, nonneutral electron plasmas were confined with a magnetic mirror at the higher field and with an electrostatic potential at the lower field.…”

Non-neutral electron plasmas confined with a nested potential in a uniform magnetic field

“…This kind of multi-ring electrode structure makes it possible to excite and detect various plasma oscillations and to provide various electric potentials. [28][29][30][31][32] An electron gun at the one end of the trap is set on the axis of symmetry and a Faraday cup is placed at the other end of the trap. The vacuum pressure is ∼5 × 10 −9 torr.…”