Experimental Investigation of Snapover: The Sudden Increase of Plasma Current Drawn to a Positively Biased Conductor When Surrounded by a Dielectric

• Main Author: Thomson, Clint D.
• Format: Others
• Published: DigitalCommons@USU 2001
• Subjects: investigation; snapover; increase; plasma; current; biased; conductor; dielectric; Physics
• Online Access: https://digitalcommons.usu.edu/etd/2092; https://digitalcommons.usu.edu/cgi/viewcontent.cgi?article=3095&context=etd

Snapover is particularly relevant to Earth-orbiting spacecraft powered by high-voltage solar arrays. During snapover, the current collected by a positively biased conductor that is immersed in a plasma suddenly increases when two conditions are met: i) there is an immediately adjacent insulator; ii) the conductor exceeds a positive threshold voltage with respect to the plasma. The enhanced current develops as a consequence of the insulator, either through secondary electron (SE) emission or by material ionization. Experiments were performed to examine snapover onset potential and current collection dependence on conductor and insulator materials, conductor size and shape, sample history, biasing rate, and contamination and smoothness of the dielectric surface. Numerous current jumps were observed between applied voltages of 100 V and 1000 V. Both surface roughening and surface coatings were found to inhibit snapover. In general, the results did not support previous simple interpretations of the SE model.