Performance improvement of a Kα source by a high-resolution thin-layer-graphite spectrometer and a polycapillary lens

A tabletop, short-pulse laser-based hard X-ray ( Kα ) source equipped with an advanced X-ray optics and dedicated for high-resolution spectroscopy and time-resolved diffraction is described. Operation of the source together with a high-resolution spectrometer containing a large-aperture highly annealed pyrolytic graphite gave a resolution E/ Δ E of ~1,800 for the spectral range around Kα line of Cu. The estimated total flux of the 8.05-keV photons was equal to 5.9 × 10 10 ph/s in 4π sr. Performance boost of the source caused by X-ray optics relied on the significant increase in the Cu- Kα photon flux on both, the sample (4.7 × 10 6 ph/s) and the detector (3.4 × 10 3 ph/s). A spectral brightness of 1.4 × 10 7 ph/s/mm 2 /mrad 2 was derived from the source parameters for the Kα line. Better performance due to high collecting power and reflectivity of the spectrometer enabled application of the cross-correlation technique with an Ni foil. An upper bound of emission duration of 323 ± 47 fs was obtained in this measurement. X-ray absorption near-edge spectroscopy on an Ni sample with an acquisition time of only 15 min confirmed the increased capability of the setup also for continuous spectrum (bremsstrahlung).