a solid electromagnetically lossy substantially gas impermeable plug fused to the interior wall of said casing passageway and to said electrode so as to partially imbed said {HEAD ~ electrode} within {TAIL ~ said plug} and completely span the remaining free cross section of said passageway, 
within
a solid electromagnetically lossy substantially gas impermeable plug fused to the interior wall of said casing passageway and to said electrode so as to partially imbed said { HEAD ~ electrode } within { TAIL ~ said plug } and completely span the remaining free cross section of said passageway ,
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH