| Polycapillary optics consist of arrays of tiny hollow glass tubes. The x rays incident at an angles smaller than a critical angle are guided down the tubes by external total reflection. Polycapillary optics can be used to shape, collimate, and focus the x-ray beam.; Polycapillary fibers were measured over a broad energy range. The transmission spectra of straight borosilicate glass single fibers were measured and were nearly flat in the 10–50 keV energy range. From the simulations and measurements, it was shown that the drop in transmission at high energies is due to fiber bending. Measurements and simulations were also performed on the behavior of leaded glass polycapillary fibers over a broad energy range. Type B leaded glass capillary optics with a length of 3–6 cm have more than 45% in the 25–50 keV transmission efficiency energy range. The low transmission at low energies is due to glass inclusions which blocking the channels. The scatter transmission of these fibers is very low, 3.6% for 3 cm length and less than 2% for 6 cm length.; A prototype collector for high energy x-rays with a 2 m focal length was characterized. Measurements of a prototype collector, performed in collimating mode, showed that the optic had high transmission up to 40 keV, good uniformity, and small exit divergence. The performance of the optic was excellent since the optic was designed accurately based on the good agreement between the computer models and single fiber data. Scatter transmission and contrast enhancement were measured in focussing mode using a parallel beam input. The optic gave better contrast than a parallel beam air gap. Contrast enhancement was measured for a small tapered optic. This tapered optic was designed to be placed into a multiple taper jig to create a large area device. Because of the removal of scatter radiation, the measured contrast enhancement for the optic was nearly factor of three at 40 keV. |
