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 ≈5µm 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 ≈(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.

Polycapillary-boosted instrument performance in the extreme ultraviolet regime for inverse photoemission spectroscopy: erratum.

We correct values and figures for the resolution of the spectrometer, as proposed in [Opt. Express25, 31840 (2017)10.1364/OE.25.031840OPEXFF1094-4087]. The new results take into account previously unknown, incoherent phase fluctuations, caused by the polycapillary lens (PCL), and estimate the realistic performance of the instrument.