Metal capillary optics: novel fabrication methods and characterization

A method for manufacturing metal monocapillary optics is described. The fabrication process begins by withdrawing an initially uniform wire from an etchant bath at a variable rate using a computer-controlled translation stage. This generates a precise taper profile on the wire that corresponds to the bore of a capillary that will be produced in subsequent steps. Paraboloidal, ellipsoidal or other capillary figures can be programmed into the motion controller. Two different methods are discussed for generating the completed optic from the etched wire. In both of these techniques, the wire functions as an expendable mandrel. In the first method, the wire is first coated with a radiation-reflecting material and then bonded to a rigid substrate. The wire is then dissolved using a chemical process to produce the hollow capillary optic. In the second method, a purely mechanical process imprints the wire figure into a softer material to create the capillary optic. Both manufacturing processes permit the production of capillaries that are accurately figured, extremely straight and have very low surface roughness. Wide latitude is possible in the selection of reflective materials that coat the internal surface of the optics. Experimental measurements using the optics with synchrotron radiation have demonstrated 5-10 μm diameter beams having flux-density gains near 100. Potential improvements to the capillaries for achieving higher gains and smaller sizes are discussed. In addition to synchrotron radiation experiments, applications with small laboratory instruments are considered. The ultimate limitations of the optics and their comparison with glass capillaries are discussed.