Performance improvement of a Kα source by a high-resolution thin-layer-graphite spectrometer and a polycapillary lens
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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/ΔE 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 × 1010 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 × 106 ph/s) and the detector (3.4 × 103 ph/s). A spectral brightness of 1.4 × 107 ph/s/mm2/mrad2 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).
PVN acknowledges support of the World Class University program (R31-2008-000-10026-0) grant provided by National Research Foundation (NRF) of Korea. HS acknowledges support by the BMBF German-Korean Collaboration Program (no. KOR 10/016). The project was also supported by the Ministry of Education, Science and Technology of Korea through Basic Science Research Program (No. R15-2008-006-03001-0), the Korea-Germany collaboration program of Korean National Research Foundation (no. 2010-00633) and by Gwangju Institute of Science and Technology through a grant from the DASAN fund and the Photonics 2020 project.
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