PPPL-4991


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<b>  Experimental Test Of Whether Electrostatically Charged Micro-organisms And Their Spores Contribute To The Onset Of Arcs Across Vacuum Gaps  </b>
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<b>Authors:</b>  L.R. Grisham, A. vonHalle, A.F. Carpe, K.R. Gilton, Guy Rossi and T.N. Stevenson
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<p><b>Abstract:</b> 
<br>  Recently it was proposed [L.R. Grisham, A. vonHalle, A.F. Carpe, Guy Rossi, K.R. Gilton, E.D. McBride, E.P. Gilson, A. Stepanov, 
T.N. Stevenson, Physics of Plasma <b>19</b> 023107 (2012)] that one of the initiators of vacuum voltage breakdown between condu cting electrodes 
might be micro-organisms and their spores, previously deposited during exposure to air, which tnen become electrostatically charged when 
an electric potential is applied across the vacuum gap.  The note describes a simple experiment to compare the number of voltage-conditioning
pulses required to reach the nominal maxium operating voltage across a gap between two metallic conductors in a vacuum, comparing cases
in which biological cleaning was done just prior to pump-down with cases where this was not done, with each preceded by exposure to ambient
air for three days.  Based upon these results, it does not appear that air-deposited microbes and their spores constitute a major pathway for arc
initiation, at least for exposure periods of a few days, and for vacuum gaps of a few millimeters, in the regime where voltage holding is
usually observed to vary linearly with gap distance.

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<b> Published in:</b> Phys. Plasmas <strong>20</strong> , 124504 (2013) </p>
<p>OSTI ID:  <a href="http://www.osti.gov/scitech/biblio/1129032" target="_parent">1129032</a><br>
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  <a href="PPPL-4991.pdf"><b>Download PPPL-4991</b></a> (pdf 275 KB / 12 pp)
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