Collimation by a polycapillary half lens at 277 eV

We report on the efficient collimation of soft X-rays with an energy of 277 eV by a halved polycapillary lens (PCL), made of borosilicate glass. Using electron-excited, micro fluorescence emission in the focus of the PCL, experiments reveal an angular divergence of (6.9 +/- 0.2) mrad in the far field of the emitted beam. For a source of approximate to 5 mu m in size, that result is confirmed by simulations, obtained with a newly developed ray tracing code. An analytical fit model is proposed and applied to characterize the evolution of the measured as well as calculated, three-dimensional (3-D) intensity distribution. The photon flux density in a free-space propagation distance of (0.4 - 0.9) m from the PCL is enhanced by a factor of approximate to(30 - 90) in comparison to the direct, not collimated radiation, as it is detected through a mm-sized transmission slit. Our findings could help to establish the halved PCL as a versatile tool in the table-top metrology of optical elements, such as mirrors and gratings for soft X-rays.(c) 2023 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement

Automated summary

This paper reports on the efficient collimation of soft X-rays with an energy of 277 eV using a halved polycapillary lens (PCL). Experimental results and simulations confirm that the PCL significantly reduces the angular divergence of the emitted beam and enhances the photon flux density. This finding is of great importance for the metrology of optical elements for soft X-rays.