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