Near-surface cusp confinement of micro-scale plasma (Past)

Ben Dankongkakul Samuel Jun Araki Richard Wirz

The development of permanent magnet microdischarge on the scale of 1 cm requires an improved understanding of magnetic cusp confinement physics very near the anode. Larger magnetically confined discharges benefit from relatively low surface-to-volume ratios, which can provide favorable electron confinement and high ionization efficiency. As a result, designers of many larger cusp confined devices, such as ring-cusp ion thrusters, have been able to yield favorable performance for large discharges by focusing on the design of the macroscopic magnetic field structure far from the magnet surfaces.,, However, these permanent magnets also result in strong microscopic cusp structures that dominate a large region in smaller discharges, a region that involves interactions between a divergent magnetic field, multiple plasma species, and the sheath conditions near the surface. The experimental effort aims to better understand cusp physics by examining plasma behavior for both a single and multi-array of permanent magnet cusps. Previous work measuring primary electron loss have shown that it is strongly influenced by the upstream magnetic field structure. The current experiments using a simplified cusp confinement geometry will determine if this behavior extends to a weakly ionized plasma. Results can then also also be used to validate computational and analytical models.