A nonneutral spheroidal plasma can be settled in a rigid rotor equilibrium inside a closed conducting cell independently of induced image charges on the cell wall if the electrostatic potential distribution on the wall surface is set equal to the sum of the external hyperbolic potential (r 2 - 2z 2) and the self-potential produced by the plasma. A confinement system equipped with a train of properly biased ring electrodes can approximately generate any axisymmetric potential, including the above field. Experiments on confinement of electron spheroids in such a system showed that the confinement time became the longest when the condition to diminish the image charge effects was satisfied. The observed frequency of the centre-of-mass harmonic oscillation of the plasma in this configuration was in good agreement with the estimated one.

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The field configuration formed by the superposition of a cusped magnetic field and an electrostatic octapole field provides a closed system of confinement for a charged particle. In a cusped magnetic field, the Störmer region which constrains a charged particle is open, but it is closed by adding a potential barrier made by the octapole field. One-component plasmas are thus expected to be confined in this configuration, preserving superior characteristics of the cusp field for plasma stability. A preliminary experiment was performed on the confinement of electrons in this field configuration. An electron plasma was confined for 3 s in a magnetic field as weak as B=50 G at the circular line cusp. The confinement time was roughly proportional to B 2, suggesting that the confinement would be improved substantially in a higher magnetic field.

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A simple method of producing an intense beam of slow positrons is proposed. X-rays radiating forward from a high Z target at the bombardment of pulsed e-beams penetrate many thin tungsten foil strips which are aligned parallel and assembled into a stack of modules with grids on one side. Stepwise electric potentials applied between the neighbouring modules produce the grid focussing field for collecting slow positrons emerging from the strip surfaces. The total wide surface area and the effective collection realize a high production rate of slow positrons above 1014 s-1 during the pulse of a 35 MeV, 0.5 A LINAC.