This provides {HEAD ~ reliable operation} of the arc for {TAIL ~ a wide range} of the cathode sizes and shapes, and at low to very high power levels 
for
This provides { HEAD ~ reliable operation } of the arc for { TAIL ~ a wide range } of the cathode sizes and shapes , and at low to very high power levels
OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH