ARCING OF NEGATIVELY BIASED SOLAR-CELLS IN A PLASMA ENVIRONMENT

Experimental and theoretical efforts have been conducted to investigat e the arcing of negatively biased solar arrays in a low-Earth orbit pl asma environment. Experiments were conducted in an ultrahigh vacuum pl asma test chamber, where the environment could be controlled carefully . Outgassing of the adhesive used to bind the protective coverglass to the solar cells was determined to be a key factor in observed arcing rates. These rates could be reduced by greater than a factor of 100 by eliminating or fully outgassing the excess adhesive remaining at the edge of the solar cells. Optical emission from solar cell arcs was obs erved to correlate linearly with arc current, both temporally and in t otal intensity. Solar cell arcing rates were also observed to scale li nearly with plasma density. The plasma scaling is in good agreement wi th a theory based on enhanced field electron emission charging of diel ectric surfaces, leading to enhanced electric fields at the conductor/ adhesive/plasma triple junction. Apparent thresholds for solar cell ar cing are reported.