Abstract: A radio frequency amplifier having a slow wave structure supported adjacent an electron beam by a support structure. The support structure includes at least one structural support member, having a supporting rod, and a dielectric material disposed on an outer surface portion of the supporting rod. The dielectric material is different from the material of the supporting rod. More particularly the dielectric material is electrically insulating having either a resistivity which reduces upon impingement of electrons from the electron beam or a secondary emission ratio that is substantially unity. The supporting rod has high thermal conductivity and is preferably boron nitride. The dielectric material is preferably titania, magnesia or beryllia.

Abstract: A laser material removal apparatus and method of removing material from a workpiece wherein a laser forms a beam of radiation having a substantially circular cross-sectional configuration, and optical means is provided for compressing portions of the beam so that the resultant focused beam will provide an image of substantially rectangular shape and uniform energy whereby improved control of the size and shape of the area to be removed is obtained.