Abstract

A new method of focusing x-rays using a tapered, hollow glass fiber is being developed. By directing an x-ray beam down the bore of such a fiber, one can obtain increased intensity since the guided radiation suffers only slight loss upon repeated total reflections from the air/glass interface of the inner wall. The fiber must be drawn so that the angle of taper of the inner diameter is small compared to the critical angle of the impinging x-rays. We have overcome this challenge by drawing fibers with taper angles as small as 0.1 milliradians. A 1.6 meter long hollow fiber with an inner diameter that decreased linearly from 470 to 110 microns was tested using monochromtic synchrotron radiation of 8.04, 13, and 20 keV as well as characteristic radiation from a conventional x-ray tube with a copper target. Transmission and focusing characteristics are reported. Intensity enhancements as large as 10 corresponding to a transmission efficiency of 54% were observed. The high efficiency of this prototype fiber supports the notion that this confinement technique should yield gains of many orders of magnitude as the optimal fiber design is achieved.

© 1990 Optical Society of America