Ion source of an ion implanter

An ion source uses at least one induction coil to generate ac magnetic field to couple rf/VHF power into a plasma within a vessel, where the excitation coil may be a single set of turns each turn having lobes or multiple separate sets of windings. The excitation coil is positioned outside and proximate that side of the vessel that is opposite to the extraction slit, and elongated parallel to the length dimension of the extraction slit. The conducting shield(s) positioned outside or integrated with the well of the vessel are used to block the capacitive coupling to the plasma and/or to collect any rf/VHF current may be coupled into the plasma. The conducting shield positioned between the vessel and the coil set can either shield the plasma from capacitive coupling from the excitation coils, or be tuned to have a higher rf/VHF voltage to ignite or clean the source.