A dielectric-loaded field applicator and an EHID lamp assembly are provided wherein the applicator comprises a helical resonator having a cylindrical dielectric core and a helical conductor, the dielectric core having a helical groove extending along its surface substantially from end to end; the helical conductor being contained in the helical groove and connectable at one end to a power source, the dielectric core being comprised of a dielectric material having a relative permittivity greater than about 3, preferably polycrystalline alumina. The EHID lamp assembly includes two opposed dielectric-loaded applicators with a discharge vessel supported between them.