Abstract: Dielectric bodies are arranged in waveguide portions for passing microwave radiation and for holding a plasma generating chamber 25 at a vacuum. The dielectric bodies are arranged to intersect at least an electron cyclotron resonance area of the waveguide portions. A tip end portion of the dielectric bodies at a side of the plasma generating chamber are positioned toward at a side of the plasma generating chamber from an intermediate portion in an axial direction length of a first permanent magnet which is arranged by enclosing an outer periphery of the waveguide portions, and a tip end portion of the dielectric bodies at a side of the plasma generating chamber is substantially consistent with an inner face of the plasma generating chamber.

Abstract: A roller for rolling mill comprising an entirely non-metallic sintered body composed principally of at least one material selected from silicon carbide, silicon nitride, sialon, alumina and zirconia and having a relative density which is at least 96% of the theoretical density, the roller having an initial crown in the range of -300 .mu.m to +300 .mu.m, is provided. This roller for rolling mill has a high hardness and high wear resistance and can be used as a work roll.

Abstract: A roller for rolling mill comprising an entirely non-metallic sintered body composed principally of at least one material selected from silicon carbide, silicon nitride, sialon, alumina and zirconia and having a relative density which is at least 96% of the theoretical density of the sintered body, the roller having an initial crown in the range of -300 .mu.m to +300 .mu.m, is provided. This roller for rolling mill has a high hardness and high wear resistance and can be used as a work roll.