The tool comprises one or more core-coil assemblies 2 jacketed in an non-magnetic and electrically insulating, tubular outer housing, 10. The housing enables high power transfer efficiency. A structural skeleton 20 extends longitudinally through the tool for axially reinforcement. The core-coil assemblies 2 are encapsulated in epoxy 77 to mechanically rigidify and protect them as well as to isolate the coil windings 51 from the power bus 23 extending longitudinally of the core-coil assemblies through a peripheral busway 60, 61.