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