404 has a proximal end 416 that is tapered to form a convex frusto conical electrode rear terminal surface 418 the plunger 406 has a plunger front contact surface 420 that is formed as a frustoconical cavity shaped to mateably receive the electrode rear terminal surface 418 the electrode 404 is configured relative to the band 412 so as to be insertable into engagement with the plunger front contact surface 420 fig1 15 illustrate an electrode supporting assembly 450 that forms another embodiment of the present invention and which has many features in common with the electrode supporting assembly 350 shown in fig7 9 the assembly 450 again has an electrode 452 that engages a plunger 454 which in turn engages a resilient element 456 that connects to a power contact element 458 these elements 454 456 458 serving to provide electrical power to the electrode 452 when biased to the electrode 39 s forward position by the resilient element 456 the electrode 452 mates with the plunger 454 as is the situation with the earlier embodiments an insulator 460 is provided having a passage 462 therethrough the passage 462 has a band 464 which partitions the passage 462 into a forward chamber 466 and a rear chamber 468 again the plunger 454 and the resilient element 456 are trapped in the rear chamber 468 this embodiment differs from the earlier electrode supporting assembly 350 in that the plunger 454 has a cylindrical extension 470 positioned between a frustoconical plunger front contact surface 472 and a collar 474 this.