Experiments on the injection, confinement, and ejection of electron clouds in a magnetic mirror

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Abstract
A cloud of (5 to 10 keV) electrons is injected into a magnetic mirror field. The magnetic field rises in 40–120 μsec to a maximum of 10 kG. Two methods of injection were tried: In the first, the injector is located at the mirror midplane and electrons are injected perpendicular to the magnetic field lines. In the second scheme, the injector is located near the mirror maximum. Up to about 1011 electrons were trapped in both schemes with a mean kinetic energy of 0.3 MeV. Measured confinement time is limited only by the magnetic field decay time. The compressed electron cloud executes electrostatic oscillations. The frequency of the oscillation is proportional to the number of electrons trapped, and it is independent of the value of the magnetic field and the initial electron energy. The electron cloud was ejected along the mirror axis and properties of the ejected electron cloud were measured by x‐ray pulses from bremstrahlung of electrons on the vacuum system wall and by collecting electrons on a Faraday cup.