Study of the optical properties of a square polycapillary slice

Conventional polycapillary X-ray lenses, which are important components of widely used X-ray optics, are very suitable for focusing or parallelling the X-rays. However, for the hexagonal arrangement of the capillary, there are some shortcomings when it is used for X-ray imaging. Although, these shortcomings can be overcome by adopting a polycapillary X-ray lens structure with a square cross-section fabricated from a square matrix array of capillaries, it is challenging to manufacture it. In this paper, we present a new type of X-ray optics: a square polycapillary slice, which is 3 mm thick. It is like a sheet and consists of 1080×1080 square arrayed square micro-channels. Each external wall of a square micro-channel can be approximately expressed as a paraboloid. To study its optical properties, we conducted both simulation and experimental measurements. The simulated results showed that the focal distances of the cases in which the square polycapillary slice had no fluctuations and had fluctuations were 36.7 ± 0.9 and 36.7 ± 1.8 mm, respectively. The measured focal distance was 36.6 ± 2.5 mm. The full widths of the simulated focal spot of the cases in which the square polycapillary slice had no fluctuations and had fluctuations were 621 and 657μm, respectively. The full width of the measured focal spot was 600μm. The centre area of the focal spot was star-like. Its optical properties were similar to those of the polycapillary X-ray lens. Because the micro-channels are squared arrayed, it is more suitable for X-ray imaging than conventional polycapillary X-ray lens.