Metal Monocapillary Optics Produced by Hydraulic Pressing

A novel method for fabricating metal monocapillary optics is described. The process begins by withdrawing an initially uniform wire from an etchant bath at a variable rate using a computer-controlled motion stage. A precisely tapered wire results, which corresponds to the bore of a capillary optic to be produced in subsequent steps. Paraboloidal, ellipsoidal, or other wire shapes can be generated. After being placed between two highly polished plates composed of a soft metal, the wire figure is symmetrically imprinted into the surfaces of both plates by the application of pressure using a hydraulic press. The completed capillary optic is produced by removing the wire; cutting and polishing the ends of the plates to define the entrance and exit apertures; and reassembling the two halves. The manufacturing process permits the production of capillaries that are accurately figured, very straight, and have low surface-roughness. Wide latitude in the selection of materials comprising the internal reflecting surface is possible by coating the plates before reassembly. Measurements using the optics with synchrotron radiation have demonstrated 5-10 μm diameter beams having flux-density gains near 100 when used with unfocused input radiation. Research applications employing the optics have been performed at SSRL. Ongoing efforts aimed at achieving significantly smaller beam sizes, higher gains, and alternative materials of construction are discussed. The ultimate limitations of the metal optics and their comparison with glass capillaries are considered