Experiments on Characteristics and Control of Positron Plasma

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Positron plasmas were successfully formed through experimental research for three years. The following results have been obtained.1.Slow positrons were generated at a time-average production rate of 6x10^<10> [e+/s] by combining a developed "Photon-Positron Converter" and a high current LINAC.2.Positron plasmas were formed by stacking pulsed slow positrons moderated with a cryogenic solid Ar film.3.A new configuration for trapping slow positrons was developed, which consists of a lot of ring electrodes. A stable rigid rotor plasma can be confined in a closed potential cell.4.Cyclotron radiation cooling in a high magnetic field was applied to get a cold positron plasma. Positrons emerging from 22Na of 3.7 MBq were first moderated by cold electrons and stacked in the trap for longer than 10^4s. Thereby, positron plasmas at room temperature in the magnetic field of 7 T were formed.5.Nonlinear mode-conversions among different electrostatic wave modes were found for spheroidal nonneutral plasmas, and also suppression of diocotron oscillations by rf-electric fields was observed.