Plasma states in a cylindrical cusp-shaped magnetic field composed of a permanent magnet array

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Abstract
In a cylindrical cusp-shaped magnetic field, spatial variations of plasma density, electric potential, electron temperature, and particle drift are investigated experimentally. Plasma parameters are observed to vary rapidly across the magnetic field in the line cusp geometry. A characteristic length of those plasma variations is in the order of a hybrid gyroradius, which is a geometric mean of an ion and electron gyroradius. The electric potential and electron temperature change little along a center axis of the line cusp. The equi-electric-potential lines are similar to the magnetic lines of force. An electron drift due to the spatial gradient of electric potential is measured by detecting electrons emitted from a small heater. It is confirmed that the observed drift velocity is comparable to both the electric velocity and the hybrid velocity which is determined from the electron temperature and the geometric mean value of an ion and an electron mass.