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