{HEAD ~ The distal ends} of the electrodes are positioned at a central volume of {TAIL ~ the airtight vessel} 
{ HEAD ~ The distal ends } of the electrodes are positioned at a central volume of { TAIL ~ the airtight vessel }
HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL