Most of {HEAD ~ the prior art designs} utilize {TAIL ~ a metal or ceramic ring} around the outer edge of the target to confine the arc, allowing the arc to travel right up to the ring 
utilize
Most of { HEAD ~ the prior art designs } utilize { TAIL ~ a metal or ceramic ring } around the outer edge of the target to confine the arc , allowing the arc to travel right up to the ring
OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH