Laboratory-device configurations for investigating new dusty-plasma equilibria

Abstract

Two configurations that are designed for laboratory investigations of dusty-plasma equilibria are being prepared for operation. The first configuration has a vertical magnetic field that confines horizontally a vertically oriented, 6.4 cm diameter, low-temperature, alkali-metal-ion plasma column. The plasma is produced via the Q-machine method (Rynn and D'Angelo 1960 Rev. Sci. Instrum. 31 1326) with contact-ionized alkali-metal ions and thermionically emitted electrons. The dust grains will be injected to form a small number of horizontal dusty-plasma layers levitated electrostatically above the plasma sheath. The advantage of using a Q-machine plasma source is the insensitivity of its plasma production to the background pressure of neutral particles. The plan is to study the competition between neutral-particle cooling and streaming-ion energization in dusty-plasma crystallization and decrystallization (i.e., freezing and melting) over a wide range of neutral-particle pressure. The second configuration has a large vacuum chamber (2 m diameter, 4 m length) and a large, solenoidal, magnetic field (0.1 T) that will magnetically confine small-diameter dust grains in a large-volume dusty plasma. The advantage of producing a large-volume, dusty plasma in a strong magnetic field is the ability to meet the criterion that the dust gyroradius is much smaller than the dusty-plasma-column diameter. The plan is to study third-component effects in microinstabilities and the influence of size distribution on magnetized dusty-plasma equilibrium and stability.