Soft X-rays with orbital angular momentum for resonant scattering experiments at Synchrotron SOLEIL

The paper presents a comprehensive description of a new setup implemented and commissioned at the SEXTANTS beamline of Synchrotron SOLEIL for absorption and scattering experiments with X-ray beams carrying an orbital angular momentum, also known as twisted X-ray beams. Two alternative methods have been implemented, based on the use of either spiral zone plates or fork grating devices, and we show how they can be used for both defining and assessing the orbital angular momentum of an X-ray beam. We also demonstrate that cascading multiple devices enables integer operations on the orbital angular momentum of the resulting X-ray beam. Finally, we report the results of the first resonant scattering pilot experiments in transmission and reflection mode, intended to assess the feasibility of future users' measurements. The availability of twisted soft X-rays complements the range of experimental techniques in elastic, resonant and coherent scattering available at the SEXTANTS beamline.