Influence of energy bandwidth of pink beam on small angle X-ray scattering

Abstract

Background: Compared with the traditional monochromatic synchrotron radiation beam, a pink beam is a quasi-monochromatic beam which can be obtained by screening a harmonic of the undulator. The energy bandwidth (Δ E/ E) of a pink beam is about 10 - 2. Despite the intensity gain from the quasi-monochromatic beam, the decrease in the energy resolution will lead the collected data to be smeared. Purpose: To study the influence of the energy bandwidth on the small angle X-ray scattering (SAXS) by experiments and verify the feasibility of SAXS with a pink beam. Method: Firstly, the influence of different energy bandwidths on SAXS has been studied by simulation and experiment. Then, TEM tests have been performed and compared with the experimental results. Result: It has been shown that the scattering curves deviate slightly from the traditional monochromatic ones. This deviation does not influence the data processing for the maximum deviation of the results is just less than 2%. In return, the gain in the intensity (one to two orders of magnitude) makes the pink beam very important for the time-resolved SAXS. Further, the results of TEM and SAXS have shown an excellent agreement. Conclusion: This work proves that the pink beam could be used for SAXS directly without a desmearing procedure. Benefiting from the increase in the beam intensity, the exposure time can be greatly shortened, thus enhancing the utilization efficiency of the synchrotron radiation.